Bump version

This PR introduces a Nix flake, allowing for InfiniTime to be built as a
Flake, including a FHS development environment.

It's derived from #1850 and
c57c57f3c6.

We also introduce `flake-compat`, allowing for non-Flake Nix mahcines to
use the project as-is, both for building (`default.nix`), and
development (`shell.nix`).

Additionally, we introduce `.envrc`, meaning that with `direnv`, the Nix
Flake is activated automatically.

Fixes #1850.

Signed-off-by: Dom Rodriguez <shymega@shymega.org.uk>

.envrc

@@ -0,0 +1 @@
+use flake

.gitmodules

@@ -4,9 +4,6 @@
 [submodule "src/libs/littlefs"]
 	path = src/libs/littlefs
 	url = https://github.com/littlefs-project/littlefs.git
-[submodule "src/libs/QCBOR"]
-	path = src/libs/QCBOR
-	url = https://github.com/laurencelundblade/QCBOR.git
 [submodule "src/libs/arduinoFFT"]
 	path = src/libs/arduinoFFT
 	url = https://github.com/kosme/arduinoFFT.git

CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.10)
 
 set(CMAKE_BUILD_TYPE Release CACHE STRING "Choose Debug or Release")
 
-project(pinetime VERSION 1.14.0 LANGUAGES C CXX ASM)
+project(pinetime VERSION 1.15.3 LANGUAGES C CXX ASM)
 
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_CXX_STANDARD 20)

default.nix

@@ -0,0 +1,10 @@
+(import
+  (
+    let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
+    fetchTarball {
+      url = lock.nodes.flake-compat.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  { src = ./.; }
+).defaultNix

flake.lock

@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-compat": {
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "revCount": 57,
+        "type": "tarball",
+        "url": "https://api.flakehub.com/f/pinned/edolstra/flake-compat/1.0.1/018afb31-abd1-7bff-a5e4-cff7e18efb7a/source.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://flakehub.com/f/edolstra/flake-compat/1.tar.gz"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1728492678,
+        "narHash": "sha256-9UTxR8eukdg+XZeHgxW5hQA9fIKHsKCdOIUycTryeVw=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "5633bcff0c6162b9e4b5f1264264611e950c8ec7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,102 @@
+{
+  description = "A very basic flake";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+    flake-compat.url = "https://flakehub.com/f/edolstra/flake-compat/1.tar.gz";
+  };
+
+  outputs = { self, ... }@inputs:
+    let
+      forAllSystems = function:
+        inputs.nixpkgs.lib.genAttrs [
+          "x86_64-linux"
+          "aarch64-linux"
+        ]
+          (system: function (import inputs.nixpkgs {
+            inherit system;
+            config.allowUnfree = true;
+          }));
+    in
+    {
+      packages = forAllSystems (pkgs:
+        let
+          infinitime-nrf5-sdk = pkgs.nrf5-sdk.overrideAttrs (old: {
+            version = "15.3.0";
+            src = pkgs.fetchzip {
+              url = "https://nsscprodmedia.blob.core.windows.net/prod/software-and-other-downloads/sdks/nrf5/binaries/nrf5sdk153059ac345.zip";
+              sha256 = "sha256-pfmhbpgVv5x2ju489XcivguwpnofHbgVA7bFUJRTj08=";
+            };
+          });
+        in
+        with pkgs; {
+          default = stdenv.mkDerivation rec {
+            name = "infinitime";
+            version = "1.14.1";
+
+            src = fetchFromGitHub {
+              owner = "InfiniTimeOrg";
+              repo = "InfiniTime";
+              rev = "refs/tags/${version}";
+              hash = "sha256-IrsN+9LgEjgfoRR6H7FhsdLMK+GLxc41IBnSbdpwv/E=";
+              fetchSubmodules = true;
+            };
+
+            nativeBuildInputs = [
+              adafruit-nrfutil
+              nodePackages.lv_font_conv
+              patch
+              python3
+              python3.pkgs.cbor
+              python3.pkgs.click
+              python3.pkgs.cryptography
+              python3.pkgs.intelhex
+              python3.pkgs.pillow
+            ];
+
+            postPatch = ''
+              # /usr/bin/env is not available in the build sandbox
+              substituteInPlace src/displayapp/fonts/generate.py --replace "'/usr/bin/env', 'patch'" "'patch'"
+              substituteInPlace tools/mcuboot/imgtool.py --replace "/usr/bin/env python3" "${python3}/bin/python3"
+            '';
+
+            cmakeFlags = [
+              ''-DARM_NONE_EABI_TOOLCHAIN_PATH=${gcc-arm-embedded-10}''
+              ''-DNRF5_SDK_PATH=${infinitime-nrf5-sdk}/share/nRF5_SDK''
+              ''-DBUILD_DFU=1''
+              ''-DBUILD_RESOURCES=1''
+              ''-DCMAKE_SOURCE_DIR=${src}''
+            ];
+
+            installPhase = ''
+              SOURCES_DIR=${src} BUILD_DIR=. OUTPUT_DIR=$out ./post_build.sh
+            '';
+          };
+        });
+
+      devShells = forAllSystems (pkgs:
+        let
+          infinitime-nrf5-sdk = pkgs.nrf5-sdk.overrideAttrs (old: {
+            version = "15.3.0";
+            src = pkgs.fetchzip {
+              url = "https://nsscprodmedia.blob.core.windows.net/prod/software-and-other-downloads/sdks/nrf5/binaries/nrf5sdk153059ac345.zip";
+              sha256 = "sha256-pfmhbpgVv5x2ju489XcivguwpnofHbgVA7bFUJRTj08=";
+            };
+          });
+        in
+        with pkgs; {
+          default =
+            mkShell {
+              packages = [
+                (writeShellScriptBin "cmake_infinitime" ''
+                  ${cmake}/bin/cmake -DARM_NONE_EABI_TOOLCHAIN_PATH="${gcc-arm-embedded-10}" \
+                        -DNRF5_SDK_PATH="${infinitime-nrf5-sdk}/share/nRF5_SDK" \
+                        "$@"
+                '')
+                ninja
+              ] ++ self.packages.${pkgs.system}.default.nativeBuildInputs;
+            };
+        });
+    };
+}
+      

shell.nix

@@ -0,0 +1,10 @@
+(import
+  (
+    let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
+    fetchTarball {
+      url = lock.nodes.flake-compat.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  { src = ./.; }
+).shellNix

src/CMakeLists.txt

@@ -411,6 +411,7 @@ list(APPEND SOURCE_FILES
         displayapp/screens/settings/SettingWeatherFormat.cpp
         displayapp/screens/settings/SettingWakeUp.cpp
         displayapp/screens/settings/SettingDisplay.cpp
+        displayapp/screens/settings/SettingHeartRate.cpp
         displayapp/screens/settings/SettingSteps.cpp
         displayapp/screens/settings/SettingSetDateTime.cpp
         displayapp/screens/settings/SettingSetDate.cpp
@@ -478,6 +479,7 @@ list(APPEND SOURCE_FILES
 
         systemtask/SystemTask.cpp
         systemtask/SystemMonitor.cpp
+        systemtask/WakeLock.cpp
         drivers/TwiMaster.cpp
 
         heartratetask/HeartRateTask.cpp
@@ -542,6 +544,7 @@ list(APPEND RECOVERY_SOURCE_FILES
 
         systemtask/SystemTask.cpp
         systemtask/SystemMonitor.cpp
+        systemtask/WakeLock.cpp
         drivers/TwiMaster.cpp
         components/rle/RleDecoder.cpp
         components/heartrate/HeartRateController.cpp
@@ -660,6 +663,7 @@ set(INCLUDE_FILES
         displayapp/InfiniTimeTheme.h
         systemtask/SystemTask.h
         systemtask/SystemMonitor.h
+        systemtask/WakeLock.h
         displayapp/screens/Symbols.h
         drivers/TwiMaster.h
         heartratetask/HeartRateTask.h

src/components/alarm/AlarmController.cpp

@@ -19,11 +19,13 @@
 #include "systemtask/SystemTask.h"
 #include "task.h"
 #include <chrono>
+#include <libraries/log/nrf_log.h>
 
 using namespace Pinetime::Controllers;
 using namespace std::chrono_literals;
 
-AlarmController::AlarmController(Controllers::DateTime& dateTimeController) : dateTimeController {dateTimeController} {
+AlarmController::AlarmController(Controllers::DateTime& dateTimeController, Controllers::FS& fs)
+  : dateTimeController {dateTimeController}, fs {fs} {
 }
 
 namespace {
@@ -36,11 +38,28 @@ namespace {
 void AlarmController::Init(System::SystemTask* systemTask) {
   this->systemTask = systemTask;
   alarmTimer = xTimerCreate("Alarm", 1, pdFALSE, this, SetOffAlarm);
+  LoadSettingsFromFile();
+  if (alarm.isEnabled) {
+    NRF_LOG_INFO("[AlarmController] Loaded alarm was enabled, scheduling");
+    ScheduleAlarm();
+  }
+}
+
+void AlarmController::SaveAlarm() {
+  // verify if it is necessary to save
+  if (alarmChanged) {
+    SaveSettingsToFile();
+  }
+  alarmChanged = false;
 }
 
 void AlarmController::SetAlarmTime(uint8_t alarmHr, uint8_t alarmMin) {
-  hours = alarmHr;
-  minutes = alarmMin;
+  if (alarm.hours == alarmHr && alarm.minutes == alarmMin) {
+    return;
+  }
+  alarm.hours = alarmHr;
+  alarm.minutes = alarmMin;
+  alarmChanged = true;
 }
 
 void AlarmController::ScheduleAlarm() {
@@ -53,18 +72,19 @@ void AlarmController::ScheduleAlarm() {
   tm* tmAlarmTime = std::localtime(&ttAlarmTime);
 
   // If the time being set has already passed today,the alarm should be set for tomorrow
-  if (hours < dateTimeController.Hours() || (hours == dateTimeController.Hours() && minutes <= dateTimeController.Minutes())) {
+  if (alarm.hours < dateTimeController.Hours() ||
+      (alarm.hours == dateTimeController.Hours() && alarm.minutes <= dateTimeController.Minutes())) {
     tmAlarmTime->tm_mday += 1;
     // tm_wday doesn't update automatically
     tmAlarmTime->tm_wday = (tmAlarmTime->tm_wday + 1) % 7;
   }
 
-  tmAlarmTime->tm_hour = hours;
-  tmAlarmTime->tm_min = minutes;
+  tmAlarmTime->tm_hour = alarm.hours;
+  tmAlarmTime->tm_min = alarm.minutes;
   tmAlarmTime->tm_sec = 0;
 
   // if alarm is in weekday-only mode, make sure it shifts to the next weekday
-  if (recurrence == RecurType::Weekdays) {
+  if (alarm.recurrence == RecurType::Weekdays) {
     if (tmAlarmTime->tm_wday == 0) { // Sunday, shift 1 day
       tmAlarmTime->tm_mday += 1;
     } else if (tmAlarmTime->tm_wday == 6) { // Saturday, shift 2 days
@@ -79,7 +99,10 @@ void AlarmController::ScheduleAlarm() {
   xTimerChangePeriod(alarmTimer, secondsToAlarm * configTICK_RATE_HZ, 0);
   xTimerStart(alarmTimer, 0);
 
-  state = AlarmState::Set;
+  if (!alarm.isEnabled) {
+    alarm.isEnabled = true;
+    alarmChanged = true;
+  }
 }
 
 uint32_t AlarmController::SecondsToAlarm() const {
@@ -88,20 +111,72 @@ uint32_t AlarmController::SecondsToAlarm() const {
 
 void AlarmController::DisableAlarm() {
   xTimerStop(alarmTimer, 0);
-  state = AlarmState::Not_Set;
+  isAlerting = false;
+  if (alarm.isEnabled) {
+    alarm.isEnabled = false;
+    alarmChanged = true;
+  }
 }
 
 void AlarmController::SetOffAlarmNow() {
-  state = AlarmState::Alerting;
+  isAlerting = true;
   systemTask->PushMessage(System::Messages::SetOffAlarm);
 }
 
 void AlarmController::StopAlerting() {
-  // Alarm state is off unless this is a recurring alarm
-  if (recurrence == RecurType::None) {
-    state = AlarmState::Not_Set;
+  isAlerting = false;
+  // Disable alarm unless it is recurring
+  if (alarm.recurrence == RecurType::None) {
+    alarm.isEnabled = false;
+    alarmChanged = true;
   } else {
     // set next instance
     ScheduleAlarm();
   }
 }
+
+void AlarmController::SetRecurrence(RecurType recurrence) {
+  if (alarm.recurrence != recurrence) {
+    alarm.recurrence = recurrence;
+    alarmChanged = true;
+  }
+}
+
+void AlarmController::LoadSettingsFromFile() {
+  lfs_file_t alarmFile;
+  AlarmSettings alarmBuffer;
+
+  if (fs.FileOpen(&alarmFile, "/.system/alarm.dat", LFS_O_RDONLY) != LFS_ERR_OK) {
+    NRF_LOG_WARNING("[AlarmController] Failed to open alarm data file");
+    return;
+  }
+
+  fs.FileRead(&alarmFile, reinterpret_cast<uint8_t*>(&alarmBuffer), sizeof(alarmBuffer));
+  fs.FileClose(&alarmFile);
+  if (alarmBuffer.version != alarmFormatVersion) {
+    NRF_LOG_WARNING("[AlarmController] Loaded alarm settings has version %u instead of %u, discarding",
+                    alarmBuffer.version,
+                    alarmFormatVersion);
+    return;
+  }
+
+  alarm = alarmBuffer;
+  NRF_LOG_INFO("[AlarmController] Loaded alarm settings from file");
+}
+
+void AlarmController::SaveSettingsToFile() const {
+  lfs_dir systemDir;
+  if (fs.DirOpen("/.system", &systemDir) != LFS_ERR_OK) {
+    fs.DirCreate("/.system");
+  }
+  fs.DirClose(&systemDir);
+  lfs_file_t alarmFile;
+  if (fs.FileOpen(&alarmFile, "/.system/alarm.dat", LFS_O_WRONLY | LFS_O_CREAT) != LFS_ERR_OK) {
+    NRF_LOG_WARNING("[AlarmController] Failed to open alarm data file for saving");
+    return;
+  }
+
+  fs.FileWrite(&alarmFile, reinterpret_cast<const uint8_t*>(&alarm), sizeof(alarm));
+  fs.FileClose(&alarmFile);
+  NRF_LOG_INFO("[AlarmController] Saved alarm settings with format version %u to file", alarm.version);
+}

src/components/alarm/AlarmController.h

@@ -30,47 +30,65 @@ namespace Pinetime {
   namespace Controllers {
     class AlarmController {
     public:
-      AlarmController(Controllers::DateTime& dateTimeController);
+      AlarmController(Controllers::DateTime& dateTimeController, Controllers::FS& fs);
 
       void Init(System::SystemTask* systemTask);
+      void SaveAlarm();
       void SetAlarmTime(uint8_t alarmHr, uint8_t alarmMin);
       void ScheduleAlarm();
       void DisableAlarm();
       void SetOffAlarmNow();
       uint32_t SecondsToAlarm() const;
       void StopAlerting();
-      enum class AlarmState { Not_Set, Set, Alerting };
       enum class RecurType { None, Daily, Weekdays };
 
       uint8_t Hours() const {
-        return hours;
+        return alarm.hours;
       }
 
       uint8_t Minutes() const {
-        return minutes;
+        return alarm.minutes;
       }
 
-      AlarmState State() const {
-        return state;
+      bool IsAlerting() const {
+        return isAlerting;
+      }
+
+      bool IsEnabled() const {
+        return alarm.isEnabled;
       }
 
       RecurType Recurrence() const {
-        return recurrence;
+        return alarm.recurrence;
       }
 
-      void SetRecurrence(RecurType recurType) {
-        recurrence = recurType;
-      }
+      void SetRecurrence(RecurType recurrence);
 
     private:
+      // Versions 255 is reserved for now, so the version field can be made
+      // bigger, should it ever be needed.
+      static constexpr uint8_t alarmFormatVersion = 1;
+
+      struct AlarmSettings {
+        uint8_t version = alarmFormatVersion;
+        uint8_t hours = 7;
+        uint8_t minutes = 0;
+        RecurType recurrence = RecurType::None;
+        bool isEnabled = false;
+      };
+
+      bool isAlerting = false;
+      bool alarmChanged = false;
+
       Controllers::DateTime& dateTimeController;
+      Controllers::FS& fs;
       System::SystemTask* systemTask = nullptr;
       TimerHandle_t alarmTimer;
-      uint8_t hours = 7;
-      uint8_t minutes = 0;
+      AlarmSettings alarm;
       std::chrono::time_point<std::chrono::system_clock, std::chrono::nanoseconds> alarmTime;
-      AlarmState state = AlarmState::Not_Set;
-      RecurType recurrence = RecurType::None;
+
+      void LoadSettingsFromFile();
+      void SaveSettingsToFile() const;
     };
   }
 }

src/components/ble/DfuService.cpp

@@ -124,9 +124,11 @@ int DfuService::WritePacketHandler(uint16_t connectionHandle, os_mbuf* om) {
                    bootloaderSize,
                    applicationSize);
 
-      // wait until SystemTask has finished waking up all devices
-      while (systemTask.IsSleeping()) {
-        vTaskDelay(50); // 50ms
+      // Wait until SystemTask has disabled sleeping
+      // This isn't quite correct, as we don't actually know
+      // if BleFirmwareUpdateStarted has been received yet
+      while (!systemTask.IsSleepDisabled()) {
+        vTaskDelay(pdMS_TO_TICKS(5));
       }
 
       dfuImage.Erase();

src/components/ble/MusicService.cpp

@@ -18,6 +18,8 @@
 #include "components/ble/MusicService.h"
 #include "components/ble/NimbleController.h"
 #include <cstring>
+#include <FreeRTOS.h>
+#include <task.h>
 
 namespace {
   // 0000yyxx-78fc-48fe-8e23-433b3a1942d0

src/components/ble/MusicService.h

@@ -25,6 +25,7 @@
 #include <host/ble_uuid.h>
 #undef max
 #undef min
+#include <FreeRTOS.h>
 
 namespace Pinetime {
   namespace Controllers {

src/components/ble/NimbleController.cpp

@@ -454,9 +454,15 @@ void NimbleController::PersistBond(struct ble_gap_conn_desc& desc) {
     /* Wakeup Spi and SpiNorFlash before accessing the file system
      * This should be fixed in the FS driver
      */
-    systemTask.PushMessage(Pinetime::System::Messages::GoToRunning);
     systemTask.PushMessage(Pinetime::System::Messages::DisableSleeping);
-    vTaskDelay(10);
+
+    // This isn't quite correct
+    // SystemTask could receive EnableSleeping right after passing this check
+    // We need some guarantee that the SystemTask has processed the above message
+    // before we can continue
+    while (!systemTask.IsSleepDisabled()) {
+      vTaskDelay(pdMS_TO_TICKS(5));
+    }
 
     lfs_file_t file_p;
 

src/components/heartrate/Ppg.cpp

@@ -142,7 +142,7 @@ Ppg::Ppg() {
   spectrum.fill(0.0f);
 }
 
-int8_t Ppg::Preprocess(uint32_t hrs, uint32_t als) {
+int8_t Ppg::Preprocess(uint16_t hrs, uint16_t als) {
   if (dataIndex < dataLength) {
     dataHRS[dataIndex++] = hrs;
   }

src/components/heartrate/Ppg.h

@@ -14,7 +14,7 @@ namespace Pinetime {
     class Ppg {
     public:
       Ppg();
-      int8_t Preprocess(uint32_t hrs, uint32_t als);
+      int8_t Preprocess(uint16_t hrs, uint16_t als);
       int HeartRate();
       void Reset(bool resetDaqBuffer);
       static constexpr int deltaTms = 100;

src/components/settings/Settings.cpp

@@ -8,13 +8,11 @@ Settings::Settings(Pinetime::Controllers::FS& fs) : fs {fs} {
 }
 
 void Settings::Init() {
-
   // Load default settings from Flash
   LoadSettingsFromFile();
 }
 
 void Settings::SaveSettings() {
-
   // verify if is necessary to save
   if (settingsChanged) {
     SaveSettingsToFile();

src/components/settings/Settings.h

@@ -50,6 +50,17 @@ namespace Pinetime {
         int colorIndex = 0;
       };
 
+      enum class HeartRateBackgroundMeasurementInterval : uint8_t {
+        Off,
+        Continuous,
+        FifteenSeconds,
+        ThirtySeconds,
+        OneMinute,
+        FiveMinutes,
+        TenMinutes,
+        ThirtyMinutes,
+      };
+
       Settings(Pinetime::Controllers::FS& fs);
 
       Settings(const Settings&) = delete;
@@ -298,10 +309,21 @@ namespace Pinetime {
         return bleRadioEnabled;
       };
 
+      HeartRateBackgroundMeasurementInterval GetHeartRateBackgroundMeasurementInterval() const {
+        return settings.heartRateBackgroundMeasurementInterval;
+      }
+
+      void SetHeartRateBackgroundMeasurementInterval(HeartRateBackgroundMeasurementInterval newHeartRateBackgroundMeasurementInterval) {
+        if (newHeartRateBackgroundMeasurementInterval != settings.heartRateBackgroundMeasurementInterval) {
+          settingsChanged = true;
+        }
+        settings.heartRateBackgroundMeasurementInterval = newHeartRateBackgroundMeasurementInterval;
+      }
+
     private:
       Pinetime::Controllers::FS& fs;
 
-      static constexpr uint32_t settingsVersion = 0x0008;
+      static constexpr uint32_t settingsVersion = 0x0009;
 
       struct SettingsData {
         uint32_t version = settingsVersion;
@@ -325,6 +347,8 @@ namespace Pinetime {
         uint16_t shakeWakeThreshold = 150;
 
         Controllers::BrightnessController::Levels brightLevel = Controllers::BrightnessController::Levels::Medium;
+
+        HeartRateBackgroundMeasurementInterval heartRateBackgroundMeasurementInterval = HeartRateBackgroundMeasurementInterval::Off;
       };
 
       SettingsData settings;

src/displayapp/DisplayApp.cpp

@@ -47,6 +47,7 @@
 #include "displayapp/screens/settings/SettingSteps.h"
 #include "displayapp/screens/settings/SettingSetDateTime.h"
 #include "displayapp/screens/settings/SettingChimes.h"
+#include "displayapp/screens/settings/SettingHeartRate.h"
 #include "displayapp/screens/settings/SettingShakeThreshold.h"
 #include "displayapp/screens/settings/SettingBluetooth.h"
 
@@ -255,9 +256,20 @@ void DisplayApp::Refresh() {
           isDimmed = true;
           brightnessController.Set(Controllers::BrightnessController::Levels::Low);
         }
-        if (IsPastSleepTime()) {
-          systemTask->PushMessage(System::Messages::GoToSleep);
-          state = States::Idle;
+        if (IsPastSleepTime() && uxQueueMessagesWaiting(msgQueue) == 0) {
+          PushMessageToSystemTask(System::Messages::GoToSleep);
+          // Can't set state to Idle here, something may send
+          // DisableSleeping before this GoToSleep arrives
+          // Instead we check we have no messages queued before sending GoToSleep
+          // This works as the SystemTask is higher priority than DisplayApp
+          // As soon as we send GoToSleep, SystemTask pre-empts DisplayApp
+          // Whenever DisplayApp is running again, it is guaranteed that
+          // SystemTask has handled the message
+          // If it responded, we will have a GoToSleep waiting in the queue
+          // By checking that there are no messages in the queue, we avoid
+          // resending GoToSleep when we already have a response
+          // SystemTask is resilient to duplicate messages, this is an
+          // optimisation to reduce pressure on the message queues
         }
       } else if (isDimmed) {
         isDimmed = false;
@@ -273,6 +285,9 @@ void DisplayApp::Refresh() {
   if (xQueueReceive(msgQueue, &msg, queueTimeout) == pdTRUE) {
     switch (msg) {
       case Messages::GoToSleep:
+        if (state != States::Running) {
+          break;
+        }
         while (brightnessController.Level() != Controllers::BrightnessController::Levels::Low) {
           brightnessController.Lower();
           vTaskDelay(100);
@@ -307,6 +322,9 @@ void DisplayApp::Refresh() {
         lv_disp_trig_activity(nullptr);
         break;
       case Messages::GoToRunning:
+        if (state == States::Running) {
+          break;
+        }
         if (settingsController.GetAlwaysOnDisplay()) {
           lcd.LowPowerOff();
         } else {
@@ -333,7 +351,7 @@ void DisplayApp::Refresh() {
         } else {
           LoadNewScreen(Apps::Timer, DisplayApp::FullRefreshDirections::Up);
         }
-        motorController.RunForDuration(35);
+        motorController.StartRinging();
         break;
       case Messages::AlarmTriggered:
         if (currentApp == Apps::Alarm) {
@@ -564,8 +582,11 @@ void DisplayApp::LoadScreen(Apps app, DisplayApp::FullRefreshDirections directio
     case Apps::SettingWakeUp:
       currentScreen = std::make_unique<Screens::SettingWakeUp>(settingsController);
       break;
+    case Apps::SettingHeartRate:
+      currentScreen = std::make_unique<Screens::SettingHeartRate>(settingsController);
+      break;
     case Apps::SettingDisplay:
-      currentScreen = std::make_unique<Screens::SettingDisplay>(this, settingsController);
+      currentScreen = std::make_unique<Screens::SettingDisplay>(settingsController);
       break;
     case Apps::SettingSteps:
       currentScreen = std::make_unique<Screens::SettingSteps>(settingsController);

src/displayapp/apps/Apps.h.in

@@ -35,6 +35,7 @@ namespace Pinetime {
       SettingWatchFace,
       SettingTimeFormat,
       SettingWeatherFormat,
+      SettingHeartRate,
       SettingDisplay,
       SettingWakeUp,
       SettingSteps,

src/displayapp/screens/Alarm.cpp

@@ -48,7 +48,7 @@ Alarm::Alarm(Controllers::AlarmController& alarmController,
              Controllers::Settings::ClockType clockType,
              System::SystemTask& systemTask,
              Controllers::MotorController& motorController)
-  : alarmController {alarmController}, systemTask {systemTask}, motorController {motorController} {
+  : alarmController {alarmController}, wakeLock(systemTask), motorController {motorController} {
 
   hourCounter.Create();
   lv_obj_align(hourCounter.GetObject(), nullptr, LV_ALIGN_IN_TOP_LEFT, 0, 0);
@@ -117,7 +117,7 @@ Alarm::Alarm(Controllers::AlarmController& alarmController,
 
   UpdateAlarmTime();
 
-  if (alarmController.State() == Controllers::AlarmController::AlarmState::Alerting) {
+  if (alarmController.IsAlerting()) {
     SetAlerting();
   } else {
     SetSwitchState(LV_ANIM_OFF);
@@ -125,14 +125,15 @@ Alarm::Alarm(Controllers::AlarmController& alarmController,
 }
 
 Alarm::~Alarm() {
-  if (alarmController.State() == AlarmController::AlarmState::Alerting) {
+  if (alarmController.IsAlerting()) {
     StopAlerting();
   }
   lv_obj_clean(lv_scr_act());
+  alarmController.SaveAlarm();
 }
 
 void Alarm::DisableAlarm() {
-  if (alarmController.State() == AlarmController::AlarmState::Set) {
+  if (alarmController.IsEnabled()) {
     alarmController.DisableAlarm();
     lv_switch_off(enableSwitch, LV_ANIM_ON);
   }
@@ -172,7 +173,7 @@ bool Alarm::OnButtonPushed() {
     HideInfo();
     return true;
   }
-  if (alarmController.State() == AlarmController::AlarmState::Alerting) {
+  if (alarmController.IsAlerting()) {
     StopAlerting();
     return true;
   }
@@ -181,7 +182,7 @@ bool Alarm::OnButtonPushed() {
 
 bool Alarm::OnTouchEvent(Pinetime::Applications::TouchEvents event) {
   // Don't allow closing the screen by swiping while the alarm is alerting
-  return alarmController.State() == AlarmController::AlarmState::Alerting && event == TouchEvents::SwipeDown;
+  return alarmController.IsAlerting() && event == TouchEvents::SwipeDown;
 }
 
 void Alarm::OnValueChanged() {
@@ -205,7 +206,7 @@ void Alarm::SetAlerting() {
   lv_obj_set_hidden(btnStop, false);
   taskStopAlarm = lv_task_create(StopAlarmTaskCallback, pdMS_TO_TICKS(60 * 1000), LV_TASK_PRIO_MID, this);
   motorController.StartRinging();
-  systemTask.PushMessage(System::Messages::DisableSleeping);
+  wakeLock.Lock();
 }
 
 void Alarm::StopAlerting() {
@@ -216,21 +217,16 @@ void Alarm::StopAlerting() {
     lv_task_del(taskStopAlarm);
     taskStopAlarm = nullptr;
   }
-  systemTask.PushMessage(System::Messages::EnableSleeping);
+  wakeLock.Release();
   lv_obj_set_hidden(enableSwitch, false);
   lv_obj_set_hidden(btnStop, true);
 }
 
 void Alarm::SetSwitchState(lv_anim_enable_t anim) {
-  switch (alarmController.State()) {
-    case AlarmController::AlarmState::Set:
-      lv_switch_on(enableSwitch, anim);
-      break;
-    case AlarmController::AlarmState::Not_Set:
-      lv_switch_off(enableSwitch, anim);
-      break;
-    default:
-      break;
+  if (alarmController.IsEnabled()) {
+    lv_switch_on(enableSwitch, anim);
+  } else {
+    lv_switch_off(enableSwitch, anim);
   }
 }
 
@@ -247,7 +243,7 @@ void Alarm::ShowInfo() {
   txtMessage = lv_label_create(btnMessage, nullptr);
   lv_obj_set_style_local_bg_color(btnMessage, LV_BTN_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_NAVY);
 
-  if (alarmController.State() == AlarmController::AlarmState::Set) {
+  if (alarmController.IsEnabled()) {
     auto timeToAlarm = alarmController.SecondsToAlarm();
 
     auto daysToAlarm = timeToAlarm / 86400;

src/displayapp/screens/Alarm.h

@@ -22,6 +22,7 @@
 #include "displayapp/screens/Screen.h"
 #include "displayapp/widgets/Counter.h"
 #include "displayapp/Controllers.h"
+#include "systemtask/WakeLock.h"
 #include "Symbols.h"
 
 namespace Pinetime {
@@ -43,7 +44,7 @@ namespace Pinetime {
 
       private:
         Controllers::AlarmController& alarmController;
-        System::SystemTask& systemTask;
+        System::WakeLock wakeLock;
         Controllers::MotorController& motorController;
 
         lv_obj_t *btnStop, *txtStop, *btnRecur, *txtRecur, *btnInfo, *enableSwitch;

src/displayapp/screens/FlashLight.cpp

@@ -15,7 +15,7 @@ namespace {
 }
 
 FlashLight::FlashLight(System::SystemTask& systemTask, Controllers::BrightnessController& brightnessController)
-  : systemTask {systemTask}, brightnessController {brightnessController} {
+  : wakeLock(systemTask), brightnessController {brightnessController} {
 
   previousBrightnessLevel = brightnessController.Level();
   brightnessController.Set(Controllers::BrightnessController::Levels::Low);
@@ -47,14 +47,13 @@ FlashLight::FlashLight(System::SystemTask& systemTask, Controllers::BrightnessCo
   backgroundAction->user_data = this;
   lv_obj_set_event_cb(backgroundAction, EventHandler);
 
-  systemTask.PushMessage(Pinetime::System::Messages::DisableSleeping);
+  wakeLock.Lock();
 }
 
 FlashLight::~FlashLight() {
   lv_obj_clean(lv_scr_act());
   lv_obj_set_style_local_bg_color(lv_scr_act(), LV_OBJ_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_BLACK);
   brightnessController.Set(previousBrightnessLevel);
-  systemTask.PushMessage(Pinetime::System::Messages::EnableSleeping);
 }
 
 void FlashLight::SetColors() {

src/displayapp/screens/FlashLight.h

@@ -3,6 +3,7 @@
 #include "displayapp/screens/Screen.h"
 #include "components/brightness/BrightnessController.h"
 #include "systemtask/SystemTask.h"
+#include "systemtask/WakeLock.h"
 #include <cstdint>
 #include <lvgl/lvgl.h>
 
@@ -23,7 +24,7 @@ namespace Pinetime {
         void SetIndicators();
         void SetColors();
 
-        Pinetime::System::SystemTask& systemTask;
+        Pinetime::System::WakeLock wakeLock;
         Controllers::BrightnessController& brightnessController;
 
         Controllers::BrightnessController::Levels brightnessLevel = Controllers::BrightnessController::Levels::High;

src/displayapp/screens/HeartRate.cpp

@@ -29,7 +29,7 @@ namespace {
 }
 
 HeartRate::HeartRate(Controllers::HeartRateController& heartRateController, System::SystemTask& systemTask)
-  : heartRateController {heartRateController}, systemTask {systemTask} {
+  : heartRateController {heartRateController}, wakeLock(systemTask) {
   bool isHrRunning = heartRateController.State() != Controllers::HeartRateController::States::Stopped;
   label_hr = lv_label_create(lv_scr_act(), nullptr);
 
@@ -63,7 +63,7 @@ HeartRate::HeartRate(Controllers::HeartRateController& heartRateController, Syst
   label_startStop = lv_label_create(btn_startStop, nullptr);
   UpdateStartStopButton(isHrRunning);
   if (isHrRunning) {
-    systemTask.PushMessage(Pinetime::System::Messages::DisableSleeping);
+    wakeLock.Lock();
   }
 
   taskRefresh = lv_task_create(RefreshTaskCallback, 100, LV_TASK_PRIO_MID, this);
@@ -72,7 +72,6 @@ HeartRate::HeartRate(Controllers::HeartRateController& heartRateController, Syst
 HeartRate::~HeartRate() {
   lv_task_del(taskRefresh);
   lv_obj_clean(lv_scr_act());
-  systemTask.PushMessage(Pinetime::System::Messages::EnableSleeping);
 }
 
 void HeartRate::Refresh() {
@@ -101,12 +100,12 @@ void HeartRate::OnStartStopEvent(lv_event_t event) {
     if (heartRateController.State() == Controllers::HeartRateController::States::Stopped) {
       heartRateController.Start();
       UpdateStartStopButton(heartRateController.State() != Controllers::HeartRateController::States::Stopped);
-      systemTask.PushMessage(Pinetime::System::Messages::DisableSleeping);
+      wakeLock.Lock();
       lv_obj_set_style_local_text_color(label_hr, LV_LABEL_PART_MAIN, LV_STATE_DEFAULT, Colors::highlight);
     } else {
       heartRateController.Stop();
       UpdateStartStopButton(heartRateController.State() != Controllers::HeartRateController::States::Stopped);
-      systemTask.PushMessage(Pinetime::System::Messages::EnableSleeping);
+      wakeLock.Release();
       lv_obj_set_style_local_text_color(label_hr, LV_LABEL_PART_MAIN, LV_STATE_DEFAULT, Colors::lightGray);
     }
   }

src/displayapp/screens/HeartRate.h

@@ -4,6 +4,7 @@
 #include <chrono>
 #include "displayapp/screens/Screen.h"
 #include "systemtask/SystemTask.h"
+#include "systemtask/WakeLock.h"
 #include "Symbols.h"
 #include <lvgl/src/lv_core/lv_style.h>
 #include <lvgl/src/lv_core/lv_obj.h>
@@ -27,7 +28,7 @@ namespace Pinetime {
 
       private:
         Controllers::HeartRateController& heartRateController;
-        Pinetime::System::SystemTask& systemTask;
+        Pinetime::System::WakeLock wakeLock;
         void UpdateStartStopButton(bool isRunning);
         lv_obj_t* label_hr;
         lv_obj_t* label_bpm;

src/displayapp/screens/Metronome.cpp

@@ -22,7 +22,7 @@ namespace {
 }
 
 Metronome::Metronome(Controllers::MotorController& motorController, System::SystemTask& systemTask)
-  : motorController {motorController}, systemTask {systemTask} {
+  : motorController {motorController}, wakeLock(systemTask) {
 
   bpmArc = lv_arc_create(lv_scr_act(), nullptr);
   bpmArc->user_data = this;
@@ -72,7 +72,6 @@ Metronome::Metronome(Controllers::MotorController& motorController, System::Syst
 
 Metronome::~Metronome() {
   lv_task_del(taskRefresh);
-  systemTask.PushMessage(System::Messages::EnableSleeping);
   lv_obj_clean(lv_scr_act());
 }
 
@@ -128,12 +127,12 @@ void Metronome::OnEvent(lv_obj_t* obj, lv_event_t event) {
         metronomeStarted = !metronomeStarted;
         if (metronomeStarted) {
           lv_label_set_text_static(lblPlayPause, Symbols::pause);
-          systemTask.PushMessage(System::Messages::DisableSleeping);
+          wakeLock.Lock();
           startTime = xTaskGetTickCount();
           counter = 1;
         } else {
           lv_label_set_text_static(lblPlayPause, Symbols::play);
-          systemTask.PushMessage(System::Messages::EnableSleeping);
+          wakeLock.Release();
         }
       }
       break;

src/displayapp/screens/Metronome.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "systemtask/SystemTask.h"
+#include "systemtask/WakeLock.h"
 #include "components/motor/MotorController.h"
 #include "displayapp/screens/Screen.h"
 #include "Symbols.h"
@@ -21,7 +22,7 @@ namespace Pinetime {
         TickType_t startTime = 0;
         TickType_t tappedTime = 0;
         Controllers::MotorController& motorController;
-        System::SystemTask& systemTask;
+        System::WakeLock wakeLock;
         int16_t bpm = 120;
         uint8_t bpb = 4;
         uint8_t counter = 1;

src/displayapp/screens/Notifications.cpp

@@ -20,7 +20,7 @@ Notifications::Notifications(DisplayApp* app,
     notificationManager {notificationManager},
     alertNotificationService {alertNotificationService},
     motorController {motorController},
-    systemTask {systemTask},
+    wakeLock(systemTask),
     mode {mode} {
 
   notificationManager.ClearNewNotificationFlag();
@@ -40,7 +40,7 @@ Notifications::Notifications(DisplayApp* app,
     validDisplay = false;
   }
   if (mode == Modes::Preview) {
-    systemTask.PushMessage(System::Messages::DisableSleeping);
+    wakeLock.Lock();
     if (notification.category == Controllers::NotificationManager::Categories::IncomingCall) {
       motorController.StartRinging();
     } else {
@@ -65,7 +65,6 @@ Notifications::~Notifications() {
   lv_task_del(taskRefresh);
   // make sure we stop any vibrations before exiting
   motorController.StopRinging();
-  systemTask.PushMessage(System::Messages::EnableSleeping);
   lv_obj_clean(lv_scr_act());
 }
 
@@ -82,7 +81,6 @@ void Notifications::Refresh() {
 
   } else if (mode == Modes::Preview && dismissingNotification) {
     running = false;
-    currentItem = std::make_unique<NotificationItem>(alertNotificationService, motorController);
 
   } else if (dismissingNotification) {
     dismissingNotification = false;
@@ -113,15 +111,15 @@ void Notifications::Refresh() {
                                                        alertNotificationService,
                                                        motorController);
     } else {
-      currentItem = std::make_unique<NotificationItem>(alertNotificationService, motorController);
+      running = false;
     }
   }
 
-  running = currentItem->IsRunning() && running;
+  running = running && currentItem->IsRunning();
 }
 
 void Notifications::OnPreviewInteraction() {
-  systemTask.PushMessage(System::Messages::EnableSleeping);
+  wakeLock.Release();
   motorController.StopRinging();
   if (timeoutLine != nullptr) {
     lv_obj_del(timeoutLine);
@@ -173,7 +171,9 @@ bool Notifications::OnTouchEvent(Pinetime::Applications::TouchEvents event) {
         } else if (nextMessage.valid) {
           currentId = nextMessage.id;
         } else {
-          // don't update id, won't be found be refresh and try to load latest message or no message box
+          // don't update id, notification manager will try to fetch
+          // but not find it. Refresh will try to load latest message
+          // or dismiss to watchface
         }
         DismissToBlack();
         return true;

src/displayapp/screens/Notifications.h

@@ -8,6 +8,7 @@
 #include "components/ble/NotificationManager.h"
 #include "components/motor/MotorController.h"
 #include "systemtask/SystemTask.h"
+#include "systemtask/WakeLock.h"
 
 namespace Pinetime {
   namespace Controllers {
@@ -73,7 +74,7 @@ namespace Pinetime {
         Pinetime::Controllers::NotificationManager& notificationManager;
         Pinetime::Controllers::AlertNotificationService& alertNotificationService;
         Pinetime::Controllers::MotorController& motorController;
-        System::SystemTask& systemTask;
+        System::WakeLock wakeLock;
         Modes mode = Modes::Normal;
         std::unique_ptr<NotificationItem> currentItem;
         Pinetime::Controllers::NotificationManager::Notification::Id currentId;

src/displayapp/screens/StopWatch.cpp

@@ -34,7 +34,7 @@ namespace {
   constexpr TickType_t blinkInterval = pdMS_TO_TICKS(1000);
 }
 
-StopWatch::StopWatch(System::SystemTask& systemTask) : systemTask {systemTask} {
+StopWatch::StopWatch(System::SystemTask& systemTask) : wakeLock(systemTask) {
   static constexpr uint8_t btnWidth = 115;
   static constexpr uint8_t btnHeight = 80;
   btnPlayPause = lv_btn_create(lv_scr_act(), nullptr);
@@ -79,7 +79,6 @@ StopWatch::StopWatch(System::SystemTask& systemTask) : systemTask {systemTask} {
 
 StopWatch::~StopWatch() {
   lv_task_del(taskRefresh);
-  systemTask.PushMessage(Pinetime::System::Messages::EnableSleeping);
   lv_obj_clean(lv_scr_act());
 }
 
@@ -135,7 +134,7 @@ void StopWatch::Start() {
   SetInterfaceRunning();
   startTime = xTaskGetTickCount();
   currentState = States::Running;
-  systemTask.PushMessage(Pinetime::System::Messages::DisableSleeping);
+  wakeLock.Lock();
 }
 
 void StopWatch::Pause() {
@@ -145,7 +144,7 @@ void StopWatch::Pause() {
   oldTimeElapsed = laps[lapsDone];
   blinkTime = xTaskGetTickCount() + blinkInterval;
   currentState = States::Halted;
-  systemTask.PushMessage(Pinetime::System::Messages::EnableSleeping);
+  wakeLock.Release();
 }
 
 void StopWatch::Refresh() {

src/displayapp/screens/StopWatch.h

@@ -7,6 +7,7 @@
 #include "portmacro_cmsis.h"
 
 #include "systemtask/SystemTask.h"
+#include "systemtask/WakeLock.h"
 #include "displayapp/apps/Apps.h"
 #include "displayapp/Controllers.h"
 #include "Symbols.h"
@@ -43,7 +44,7 @@ namespace Pinetime {
         void Start();
         void Pause();
 
-        Pinetime::System::SystemTask& systemTask;
+        Pinetime::System::WakeLock wakeLock;
         States currentState = States::Init;
         TickType_t startTime;
         TickType_t oldTimeElapsed = 0;

src/displayapp/screens/SystemInfo.cpp

@@ -40,8 +40,7 @@ SystemInfo::SystemInfo(Pinetime::Applications::DisplayApp* app,
                        Pinetime::Controllers::MotionController& motionController,
                        const Pinetime::Drivers::Cst816S& touchPanel,
                        const Pinetime::Drivers::SpiNorFlash& spiNorFlash)
-  : app {app},
-    dateTimeController {dateTimeController},
+  : dateTimeController {dateTimeController},
     batteryController {batteryController},
     brightnessController {brightnessController},
     bleController {bleController},

src/displayapp/screens/SystemInfo.h

@@ -35,7 +35,6 @@ namespace Pinetime {
         bool OnTouchEvent(TouchEvents event) override;
 
       private:
-        DisplayApp* app;
         Pinetime::Controllers::DateTime& dateTimeController;
         const Pinetime::Controllers::Battery& batteryController;
         Pinetime::Controllers::BrightnessController& brightnessController;

src/displayapp/screens/settings/SettingDisplay.cpp

@@ -24,8 +24,7 @@ namespace {
 
 constexpr std::array<uint16_t, 6> SettingDisplay::options;
 
-SettingDisplay::SettingDisplay(Pinetime::Applications::DisplayApp* app, Pinetime::Controllers::Settings& settingsController)
-  : app {app}, settingsController {settingsController} {
+SettingDisplay::SettingDisplay(Pinetime::Controllers::Settings& settingsController) : settingsController {settingsController} {
 
   lv_obj_t* container1 = lv_cont_create(lv_scr_act(), nullptr);
 

src/displayapp/screens/settings/SettingDisplay.h

@@ -14,14 +14,13 @@ namespace Pinetime {
 
       class SettingDisplay : public Screen {
       public:
-        SettingDisplay(DisplayApp* app, Pinetime::Controllers::Settings& settingsController);
+        SettingDisplay(Pinetime::Controllers::Settings& settingsController);
         ~SettingDisplay() override;
 
         void UpdateSelected(lv_obj_t* object, lv_event_t event);
         void ToggleAlwaysOn();
 
       private:
-        DisplayApp* app;
         static constexpr std::array<uint16_t, 6> options = {5000, 7000, 10000, 15000, 20000, 30000};
 
         Controllers::Settings& settingsController;

src/displayapp/screens/settings/SettingHeartRate.cpp

@@ -0,0 +1,75 @@
+#include "displayapp/screens/settings/SettingHeartRate.h"
+#include <lvgl/lvgl.h>
+#include "displayapp/screens/Styles.h"
+#include "displayapp/screens/Screen.h"
+#include "displayapp/screens/Symbols.h"
+#include <array>
+#include <algorithm>
+
+using namespace Pinetime::Applications::Screens;
+
+namespace {
+  void event_handler(lv_obj_t* obj, lv_event_t event) {
+    auto* screen = static_cast<SettingHeartRate*>(obj->user_data);
+    screen->UpdateSelected(obj, event);
+  }
+}
+
+constexpr std::array<Option, 8> SettingHeartRate::options;
+
+SettingHeartRate::SettingHeartRate(Pinetime::Controllers::Settings& settingsController) : settingsController {settingsController} {
+
+  lv_obj_t* container1 = lv_cont_create(lv_scr_act(), nullptr);
+
+  lv_obj_set_style_local_bg_opa(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, LV_OPA_TRANSP);
+  lv_obj_set_style_local_pad_all(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, 5);
+  lv_obj_set_style_local_pad_inner(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, 5);
+  lv_obj_set_style_local_border_width(container1, LV_CONT_PART_MAIN, LV_STATE_DEFAULT, 0);
+
+  lv_obj_set_pos(container1, 10, 60);
+  lv_obj_set_width(container1, LV_HOR_RES - 20);
+  lv_obj_set_height(container1, LV_VER_RES - 50);
+  lv_cont_set_layout(container1, LV_LAYOUT_PRETTY_TOP);
+
+  lv_obj_t* title = lv_label_create(lv_scr_act(), nullptr);
+  lv_label_set_text_static(title, "Backg. Interval");
+  lv_label_set_text(title, "Backg. Interval");
+  lv_label_set_align(title, LV_LABEL_ALIGN_CENTER);
+  lv_obj_align(title, lv_scr_act(), LV_ALIGN_IN_TOP_MID, 10, 15);
+
+  lv_obj_t* icon = lv_label_create(lv_scr_act(), nullptr);
+  lv_obj_set_style_local_text_color(icon, LV_LABEL_PART_MAIN, LV_STATE_DEFAULT, LV_COLOR_RED);
+  lv_label_set_text_static(icon, Symbols::heartBeat);
+  lv_label_set_align(icon, LV_LABEL_ALIGN_CENTER);
+  lv_obj_align(icon, title, LV_ALIGN_OUT_LEFT_MID, -10, 0);
+
+  for (unsigned int i = 0; i < options.size(); i++) {
+    cbOption[i] = lv_checkbox_create(container1, nullptr);
+    lv_checkbox_set_text(cbOption[i], options[i].name);
+    cbOption[i]->user_data = this;
+    lv_obj_set_event_cb(cbOption[i], event_handler);
+    SetRadioButtonStyle(cbOption[i]);
+
+    if (settingsController.GetHeartRateBackgroundMeasurementInterval() == options[i].interval) {
+      lv_checkbox_set_checked(cbOption[i], true);
+    }
+  }
+}
+
+SettingHeartRate::~SettingHeartRate() {
+  lv_obj_clean(lv_scr_act());
+  settingsController.SaveSettings();
+}
+
+void SettingHeartRate::UpdateSelected(lv_obj_t* object, lv_event_t event) {
+  if (event == LV_EVENT_CLICKED) {
+    for (unsigned int i = 0; i < options.size(); i++) {
+      if (object == cbOption[i]) {
+        lv_checkbox_set_checked(cbOption[i], true);
+        settingsController.SetHeartRateBackgroundMeasurementInterval(options[i].interval);
+      } else {
+        lv_checkbox_set_checked(cbOption[i], false);
+      }
+    }
+  }
+}

src/displayapp/screens/settings/SettingHeartRate.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <cstdint>
+#include <lvgl/lvgl.h>
+
+#include "components/settings/Settings.h"
+#include "displayapp/screens/ScreenList.h"
+#include "displayapp/screens/Screen.h"
+#include "displayapp/screens/Symbols.h"
+#include "displayapp/screens/CheckboxList.h"
+
+namespace Pinetime {
+
+  namespace Applications {
+    namespace Screens {
+
+      struct Option {
+        const Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval interval;
+        const char* name;
+      };
+
+      class SettingHeartRate : public Screen {
+      public:
+        SettingHeartRate(Pinetime::Controllers::Settings& settings);
+        ~SettingHeartRate() override;
+
+        void UpdateSelected(lv_obj_t* object, lv_event_t event);
+
+      private:
+        Pinetime::Controllers::Settings& settingsController;
+
+        static constexpr std::array<Option, 8> options = {{
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::Off, " Off"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::Continuous, "Cont"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::FifteenSeconds, " 15s"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::ThirtySeconds, " 30s"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::OneMinute, "  1m"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::FiveMinutes, "  5m"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::TenMinutes, " 10m"},
+          {Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::ThirtyMinutes, " 30m"},
+        }};
+
+        lv_obj_t* cbOption[options.size()];
+      };
+    }
+  }
+}

src/displayapp/screens/settings/SettingSetDateTime.cpp

@@ -15,8 +15,7 @@ bool SettingSetDateTime::OnTouchEvent(Pinetime::Applications::TouchEvents event)
 SettingSetDateTime::SettingSetDateTime(Pinetime::Applications::DisplayApp* app,
                                        Pinetime::Controllers::DateTime& dateTimeController,
                                        Pinetime::Controllers::Settings& settingsController)
-  : app {app},
-    dateTimeController {dateTimeController},
+  : dateTimeController {dateTimeController},
     settingsController {settingsController},
     screens {app,
              0,

src/displayapp/screens/settings/SettingSetDateTime.h

@@ -20,7 +20,6 @@ namespace Pinetime {
         void Quit();
 
       private:
-        DisplayApp* app;
         Controllers::DateTime& dateTimeController;
         Controllers::Settings& settingsController;
 

src/displayapp/screens/settings/SettingWatchFace.cpp

@@ -54,8 +54,7 @@ SettingWatchFace::SettingWatchFace(Pinetime::Applications::DisplayApp* app,
                                    std::array<Screens::SettingWatchFace::Item, UserWatchFaceTypes::Count>&& watchfaceItems,
                                    Pinetime::Controllers::Settings& settingsController,
                                    Pinetime::Controllers::FS& filesystem)
-  : app {app},
-    watchfaceItems {std::move(watchfaceItems)},
+  : watchfaceItems {std::move(watchfaceItems)},
     settingsController {settingsController},
     filesystem {filesystem},
     screens {app, 0, CreateScreenList(), Screens::ScreenListModes::UpDown} {

src/displayapp/screens/settings/SettingWatchFace.h

@@ -34,7 +34,6 @@ namespace Pinetime {
         bool OnTouchEvent(TouchEvents event) override;
 
       private:
-        DisplayApp* app;
         auto CreateScreenList() const;
         std::unique_ptr<Screen> CreateScreen(unsigned int screenNum) const;
 

src/displayapp/screens/settings/Settings.h

@@ -38,15 +38,16 @@ namespace Pinetime {
           {Symbols::home, "Watch face", Apps::SettingWatchFace},
 
           {Symbols::shoe, "Steps", Apps::SettingSteps},
+          {Symbols::heartBeat, "Heartrate", Apps::SettingHeartRate},
           {Symbols::clock, "Date&Time", Apps::SettingSetDateTime},
           {Symbols::cloudSunRain, "Weather", Apps::SettingWeatherFormat},
-          {Symbols::batteryHalf, "Battery", Apps::BatteryInfo},
 
+          {Symbols::batteryHalf, "Battery", Apps::BatteryInfo},
           {Symbols::clock, "Chimes", Apps::SettingChimes},
           {Symbols::tachometer, "Shake Calib.", Apps::SettingShakeThreshold},
           {Symbols::check, "Firmware", Apps::FirmwareValidation},
-          {Symbols::bluetooth, "Bluetooth", Apps::SettingBluetooth},
 
+          {Symbols::bluetooth, "Bluetooth", Apps::SettingBluetooth},
           {Symbols::list, "About", Apps::SysInfo},
 
           // {Symbols::none, "None", Apps::None},

src/drivers/Hrs3300.cpp

@@ -6,6 +6,7 @@
 
 #include "drivers/Hrs3300.h"
 #include <algorithm>
+#include <iterator>
 #include <nrf_gpio.h>
 
 #include <FreeRTOS.h>
@@ -67,40 +68,37 @@ void Hrs3300::Disable() {
   WriteRegister(static_cast<uint8_t>(Registers::PDriver), 0);
 }
 
-uint32_t Hrs3300::ReadHrs() {
-  auto m = ReadRegister(static_cast<uint8_t>(Registers::C0DataM));
-  auto h = ReadRegister(static_cast<uint8_t>(Registers::C0DataH));
-  auto l = ReadRegister(static_cast<uint8_t>(Registers::C0dataL));
-  return ((l & 0x30) << 12) | (m << 8) | ((h & 0x0f) << 4) | (l & 0x0f);
-}
+Hrs3300::PackedHrsAls Hrs3300::ReadHrsAls() {
+  constexpr Registers dataRegisters[] =
+    {Registers::C1dataM, Registers::C0DataM, Registers::C0DataH, Registers::C1dataH, Registers::C1dataL, Registers::C0dataL};
+  // Calculate smallest register address
+  constexpr uint8_t baseOffset = static_cast<uint8_t>(*std::min_element(std::begin(dataRegisters), std::end(dataRegisters)));
+  // Calculate largest address to determine length of read needed
+  // Add one to largest relative index to find the length
+  constexpr uint8_t length = static_cast<uint8_t>(*std::max_element(std::begin(dataRegisters), std::end(dataRegisters))) - baseOffset + 1;
 
-uint32_t Hrs3300::ReadAls() {
-  auto m = ReadRegister(static_cast<uint8_t>(Registers::C1dataM));
-  auto h = ReadRegister(static_cast<uint8_t>(Registers::C1dataH));
-  auto l = ReadRegister(static_cast<uint8_t>(Registers::C1dataL));
-  return ((h & 0x3f) << 11) | (m << 3) | (l & 0x07);
-}
-
-void Hrs3300::SetGain(uint8_t gain) {
-  constexpr uint8_t maxGain = 64U;
-  gain = std::min(gain, maxGain);
-  uint8_t hgain = 0;
-  while ((1 << hgain) < gain) {
-    ++hgain;
+  Hrs3300::PackedHrsAls res;
+  uint8_t buf[length];
+  auto ret = twiMaster.Read(twiAddress, baseOffset, buf, length);
+  if (ret != TwiMaster::ErrorCodes::NoError) {
+    NRF_LOG_INFO("READ ERROR");
   }
+  // hrs
+  uint8_t m = static_cast<uint8_t>(Registers::C0DataM) - baseOffset;
+  uint8_t h = static_cast<uint8_t>(Registers::C0DataH) - baseOffset;
+  uint8_t l = static_cast<uint8_t>(Registers::C0dataL) - baseOffset;
+  // There are two extra bits (17 and 18) but they are not read here
+  // as resolutions >16bit aren't practically useful (too slow) and
+  // all hrs values throughout InfiniTime are 16bit
+  res.hrs = (buf[m] << 8) | ((buf[h] & 0x0f) << 4) | (buf[l] & 0x0f);
 
-  WriteRegister(static_cast<uint8_t>(Registers::Hgain), hgain << 2);
-}
+  // als
+  m = static_cast<uint8_t>(Registers::C1dataM) - baseOffset;
+  h = static_cast<uint8_t>(Registers::C1dataH) - baseOffset;
+  l = static_cast<uint8_t>(Registers::C1dataL) - baseOffset;
+  res.als = ((buf[h] & 0x3f) << 11) | (buf[m] << 3) | (buf[l] & 0x07);
 
-void Hrs3300::SetDrive(uint8_t drive) {
-  auto en = ReadRegister(static_cast<uint8_t>(Registers::Enable));
-  auto pd = ReadRegister(static_cast<uint8_t>(Registers::PDriver));
-
-  en = (en & 0xf7) | ((drive & 2) << 2);
-  pd = (pd & 0xbf) | ((drive & 1) << 6);
-
-  WriteRegister(static_cast<uint8_t>(Registers::Enable), en);
-  WriteRegister(static_cast<uint8_t>(Registers::PDriver), pd);
+  return res;
 }
 
 void Hrs3300::WriteRegister(uint8_t reg, uint8_t data) {

src/drivers/Hrs3300.h

@@ -21,6 +21,11 @@ namespace Pinetime {
         Hgain = 0x17
       };
 
+      struct PackedHrsAls {
+        uint16_t hrs;
+        uint16_t als;
+      };
+
       Hrs3300(TwiMaster& twiMaster, uint8_t twiAddress);
       Hrs3300(const Hrs3300&) = delete;
       Hrs3300& operator=(const Hrs3300&) = delete;
@@ -30,10 +35,7 @@ namespace Pinetime {
       void Init();
       void Enable();
       void Disable();
-      uint32_t ReadHrs();
-      uint32_t ReadAls();
-      void SetGain(uint8_t gain);
-      void SetDrive(uint8_t drive);
+      PackedHrsAls ReadHrsAls();
 
     private:
       TwiMaster& twiMaster;

src/heartratetask/HeartRateTask.cpp

@@ -5,8 +5,23 @@
 
 using namespace Pinetime::Applications;
 
-HeartRateTask::HeartRateTask(Drivers::Hrs3300& heartRateSensor, Controllers::HeartRateController& controller)
-  : heartRateSensor {heartRateSensor}, controller {controller} {
+TickType_t CurrentTaskDelay(HeartRateTask::States state, TickType_t ppgDeltaTms) {
+  switch (state) {
+    case HeartRateTask::States::ScreenOnAndMeasuring:
+    case HeartRateTask::States::ScreenOffAndMeasuring:
+      return ppgDeltaTms;
+    case HeartRateTask::States::ScreenOffAndWaiting:
+      return pdMS_TO_TICKS(1000);
+    default:
+      return portMAX_DELAY;
+  }
+}
+
+
+HeartRateTask::HeartRateTask(Drivers::Hrs3300& heartRateSensor,
+                             Controllers::HeartRateController& controller,
+                             Controllers::Settings& settings)
+  : heartRateSensor {heartRateSensor}, controller {controller}, settings {settings} {
 }
 
 void HeartRateTask::Start() {
@@ -25,77 +40,40 @@ void HeartRateTask::Process(void* instance) {
 
 void HeartRateTask::Work() {
   int lastBpm = 0;
-  while (true) {
-    Messages msg;
-    uint32_t delay;
-    if (state == States::Running) {
-      if (measurementStarted) {
-        delay = ppg.deltaTms;
-      } else {
-        delay = 100;
-      }
-    } else {
-      delay = portMAX_DELAY;
-    }
 
-    if (xQueueReceive(messageQueue, &msg, delay)) {
+  while (true) {
+    TickType_t delay = CurrentTaskDelay(state, ppg.deltaTms);
+    Messages msg;
+
+    if (xQueueReceive(messageQueue, &msg, delay) == pdTRUE) {
       switch (msg) {
         case Messages::GoToSleep:
-          StopMeasurement();
-          state = States::Idle;
+          HandleGoToSleep();
           break;
         case Messages::WakeUp:
-          state = States::Running;
-          if (measurementStarted) {
-            lastBpm = 0;
-            StartMeasurement();
-          }
+          HandleWakeUp();
           break;
         case Messages::StartMeasurement:
-          if (measurementStarted) {
-            break;
-          }
-          lastBpm = 0;
-          StartMeasurement();
-          measurementStarted = true;
+          HandleStartMeasurement(&lastBpm);
           break;
         case Messages::StopMeasurement:
-          if (!measurementStarted) {
-            break;
-          }
-          StopMeasurement();
-          measurementStarted = false;
+          HandleStopMeasurement();
           break;
       }
     }
 
-    if (measurementStarted) {
-      int8_t ambient = ppg.Preprocess(heartRateSensor.ReadHrs(), heartRateSensor.ReadAls());
-      int bpm = ppg.HeartRate();
-
-      // If ambient light detected or a reset requested (bpm < 0)
-      if (ambient > 0) {
-        // Reset all DAQ buffers
-        ppg.Reset(true);
-        // Force state to NotEnoughData (below)
-        lastBpm = 0;
-        bpm = 0;
-      } else if (bpm < 0) {
-        // Reset all DAQ buffers except HRS buffer
-        ppg.Reset(false);
-        // Set HR to zero and update
-        bpm = 0;
-        controller.Update(Controllers::HeartRateController::States::Running, bpm);
-      }
-
-      if (lastBpm == 0 && bpm == 0) {
-        controller.Update(Controllers::HeartRateController::States::NotEnoughData, bpm);
-      }
-
-      if (bpm != 0) {
-        lastBpm = bpm;
-        controller.Update(Controllers::HeartRateController::States::Running, lastBpm);
-      }
+    switch (state) {
+      case States::ScreenOffAndWaiting:
+        HandleBackgroundWaiting();
+        break;
+      case States::ScreenOffAndMeasuring:
+      case States::ScreenOnAndMeasuring:
+        HandleSensorData(&lastBpm);
+        break;
+      case States::ScreenOffAndStopped:
+      case States::ScreenOnAndStopped:
+        // nothing to do -> ignore
+        break;
     }
   }
 }
@@ -110,6 +88,7 @@ void HeartRateTask::StartMeasurement() {
   heartRateSensor.Enable();
   ppg.Reset(true);
   vTaskDelay(100);
+  measurementStart = xTaskGetTickCount();
 }
 
 void HeartRateTask::StopMeasurement() {
@@ -117,3 +96,182 @@ void HeartRateTask::StopMeasurement() {
   ppg.Reset(true);
   vTaskDelay(100);
 }
+
+void HeartRateTask::HandleGoToSleep() {
+  switch (state) {
+    case States::ScreenOnAndStopped:
+      state = States::ScreenOffAndStopped;
+      break;
+    case States::ScreenOnAndMeasuring:
+      state = States::ScreenOffAndMeasuring;
+      break;
+    case States::ScreenOffAndStopped:
+    case States::ScreenOffAndWaiting:
+    case States::ScreenOffAndMeasuring:
+      // shouldn't happen -> ignore
+      break;
+  }
+}
+
+void HeartRateTask::HandleWakeUp() {
+  switch (state) {
+    case States::ScreenOffAndStopped:
+      state = States::ScreenOnAndStopped;
+      break;
+    case States::ScreenOffAndMeasuring:
+      state = States::ScreenOnAndMeasuring;
+      break;
+    case States::ScreenOffAndWaiting:
+      state = States::ScreenOnAndMeasuring;
+      StartMeasurement();
+      break;
+    case States::ScreenOnAndStopped:
+    case States::ScreenOnAndMeasuring:
+      // shouldn't happen -> ignore
+      break;
+  }
+}
+
+void HeartRateTask::HandleStartMeasurement(int* lastBpm) {
+  switch (state) {
+    case States::ScreenOffAndStopped:
+    case States::ScreenOnAndStopped:
+      state = States::ScreenOnAndMeasuring;
+      *lastBpm = 0;
+      StartMeasurement();
+      break;
+    case States::ScreenOnAndMeasuring:
+    case States::ScreenOffAndMeasuring:
+    case States::ScreenOffAndWaiting:
+      // shouldn't happen -> ignore
+      break;
+  }
+}
+
+void HeartRateTask::HandleStopMeasurement() {
+  switch (state) {
+    case States::ScreenOnAndMeasuring:
+      state = States::ScreenOnAndStopped;
+      StopMeasurement();
+      break;
+    case States::ScreenOffAndMeasuring:
+    case States::ScreenOffAndWaiting:
+      state = States::ScreenOffAndStopped;
+      StopMeasurement();
+      break;
+    case States::ScreenOnAndStopped:
+    case States::ScreenOffAndStopped:
+      // shouldn't happen -> ignore
+      break;
+  }
+}
+
+void HeartRateTask::HandleBackgroundWaiting() {
+  if (!IsBackgroundMeasurementActivated()) {
+    return;
+  }
+
+  if (ShouldStartBackgroundMeasuring()) {
+    state = States::ScreenOffAndMeasuring;
+    StartMeasurement();
+  }
+}
+
+void HeartRateTask::HandleSensorData(int* lastBpm) {
+  int8_t ambient = ppg.Preprocess(heartRateSensor.ReadHrs(), heartRateSensor.ReadAls());
+  int bpm = ppg.HeartRate();
+
+  // If ambient light detected or a reset requested (bpm < 0)
+  if (ambient > 0) {
+    // Reset all DAQ buffers
+    ppg.Reset(true);
+  } else if (bpm < 0) {
+    // Reset all DAQ buffers except HRS buffer
+    ppg.Reset(false);
+    // Set HR to zero and update
+    bpm = 0;
+  }
+
+  bool notEnoughData = *lastBpm == 0 && bpm == 0;
+  if (notEnoughData) {
+    controller.Update(Controllers::HeartRateController::States::NotEnoughData, bpm);
+  }
+
+  if (bpm != 0) {
+    *lastBpm = bpm;
+    controller.Update(Controllers::HeartRateController::States::Running, bpm);
+  }
+
+  if (state == States::ScreenOnAndMeasuring || IsContinuousModeActivated()) {
+    return;
+  } 
+
+  // state == States::ScreenOffAndMeasuring 
+  //    (because state != ScreenOnAndMeasuring and the only state that enables measuring is ScreenOffAndMeasuring)
+  // !IsContinuousModeActivated()
+
+  if (ShouldStartBackgroundMeasuring()) {
+    // This doesn't change the state but resets the measurment timer, which basically starts the next measurment without resetting the sensor.
+    // This is basically a fall back to continuous mode, when measurments take too long.
+    measurementStart = xTaskGetTickCount();
+    return;
+  }
+
+  bool noDataWithinTimeLimit = bpm == 0 && ShoudStopTryingToGetData();
+  bool dataWithinTimeLimit = bpm != 0;
+  if (dataWithinTimeLimit || noDataWithinTimeLimit) {
+    state = States::ScreenOffAndWaiting;
+    StopMeasurement();
+  }
+
+}
+
+TickType_t HeartRateTask::GetHeartRateBackgroundMeasurementIntervalInTicks() {
+  int ms;
+  switch (settings.GetHeartRateBackgroundMeasurementInterval()) {
+    case Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::FifteenSeconds:
+      ms = 15 * 1000;
+      break;
+    case Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::ThirtySeconds:
+      ms = 30 * 1000;
+      break;
+    case Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::OneMinute:
+      ms = 60 * 1000;
+      break;
+    case Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::FiveMinutes:
+      ms = 5 * 60 * 1000;
+      break;
+    case Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::TenMinutes:
+      ms = 10 * 60 * 1000;
+      break;
+    case Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::ThirtyMinutes:
+      ms = 30 * 60 * 1000;
+      break;
+    default:
+      ms = 0;
+      break;
+  }
+  return pdMS_TO_TICKS(ms);
+}
+
+bool HeartRateTask::IsContinuousModeActivated() {
+  return settings.GetHeartRateBackgroundMeasurementInterval() ==
+         Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::Continuous;
+}
+
+bool HeartRateTask::IsBackgroundMeasurementActivated() {
+  return settings.GetHeartRateBackgroundMeasurementInterval() !=
+         Pinetime::Controllers::Settings::HeartRateBackgroundMeasurementInterval::Off;
+}
+
+TickType_t HeartRateTask::GetTicksSinceLastMeasurementStarted() {
+  return xTaskGetTickCount() - measurementStart;
+}
+
+bool HeartRateTask::ShoudStopTryingToGetData() {
+  return GetTicksSinceLastMeasurementStarted() >= DURATION_UNTIL_BACKGROUND_MEASUREMENT_IS_STOPPED;
+}
+
+bool HeartRateTask::ShouldStartBackgroundMeasuring() {
+  return GetTicksSinceLastMeasurementStarted() >= GetHeartRateBackgroundMeasurementIntervalInTicks();
+}

src/heartratetask/HeartRateTask.h

@@ -3,6 +3,9 @@
 #include <task.h>
 #include <queue.h>
 #include <components/heartrate/Ppg.h>
+#include "components/settings/Settings.h"
+
+#define DURATION_UNTIL_BACKGROUND_MEASUREMENT_IS_STOPPED pdMS_TO_TICKS(30 * 1000)
 
 namespace Pinetime {
   namespace Drivers {
@@ -16,10 +19,24 @@ namespace Pinetime {
   namespace Applications {
     class HeartRateTask {
     public:
-      enum class Messages : uint8_t { GoToSleep, WakeUp, StartMeasurement, StopMeasurement };
-      enum class States { Idle, Running };
+      enum class Messages : uint8_t {
+        GoToSleep,
+        WakeUp,
+        StartMeasurement,
+        StopMeasurement
+      };
 
-      explicit HeartRateTask(Drivers::Hrs3300& heartRateSensor, Controllers::HeartRateController& controller);
+      enum class States {
+        ScreenOnAndStopped,
+        ScreenOnAndMeasuring,
+        ScreenOffAndStopped,
+        ScreenOffAndWaiting,
+        ScreenOffAndMeasuring
+      };
+
+      explicit HeartRateTask(Drivers::Hrs3300& heartRateSensor,
+                             Controllers::HeartRateController& controller,
+                             Controllers::Settings& settings);
       void Start();
       void Work();
       void PushMessage(Messages msg);
@@ -29,13 +46,30 @@ namespace Pinetime {
       void StartMeasurement();
       void StopMeasurement();
 
+      void HandleGoToSleep();
+      void HandleWakeUp();
+      void HandleStartMeasurement(int* lastBpm);
+      void HandleStopMeasurement();
+
+      void HandleBackgroundWaiting();
+      void HandleSensorData(int* lastBpm);
+
+      TickType_t GetHeartRateBackgroundMeasurementIntervalInTicks();
+      bool IsContinuousModeActivated();
+      bool IsBackgroundMeasurementActivated();
+
+      TickType_t GetTicksSinceLastMeasurementStarted();
+      bool ShoudStopTryingToGetData();
+      bool ShouldStartBackgroundMeasuring();
+
       TaskHandle_t taskHandle;
       QueueHandle_t messageQueue;
-      States state = States::Running;
+      States state = States::ScreenOnAndStopped;
       Drivers::Hrs3300& heartRateSensor;
       Controllers::HeartRateController& controller;
+      Controllers::Settings& settings;
       Controllers::Ppg ppg;
-      bool measurementStarted = false;
+      TickType_t measurementStart = 0;
     };
 
   }

src/libs/QCBOR

@@ -1 +0,0 @@
-Subproject commit 56b17bf9f74096774944bcac0829adcd887d391e

src/main.cpp

@@ -93,18 +93,18 @@ TimerHandle_t debounceChargeTimer;
 Pinetime::Controllers::Battery batteryController;
 Pinetime::Controllers::Ble bleController;
 
-Pinetime::Controllers::HeartRateController heartRateController;
-Pinetime::Applications::HeartRateTask heartRateApp(heartRateSensor, heartRateController);
-
 Pinetime::Controllers::FS fs {spiNorFlash};
 Pinetime::Controllers::Settings settingsController {fs};
 Pinetime::Controllers::MotorController motorController {};
 
+Pinetime::Controllers::HeartRateController heartRateController;
+Pinetime::Applications::HeartRateTask heartRateApp(heartRateSensor, heartRateController, settingsController);
+
 Pinetime::Controllers::DateTime dateTimeController {settingsController};
 Pinetime::Drivers::Watchdog watchdog;
 Pinetime::Controllers::NotificationManager notificationManager;
 Pinetime::Controllers::MotionController motionController;
-Pinetime::Controllers::AlarmController alarmController {dateTimeController};
+Pinetime::Controllers::AlarmController alarmController {dateTimeController, fs};
 Pinetime::Controllers::TouchHandler touchHandler;
 Pinetime::Controllers::ButtonHandler buttonHandler;
 Pinetime::Controllers::BrightnessController brightnessController {};

src/systemtask/SystemTask.cpp

@@ -189,36 +189,14 @@ void SystemTask::Work() {
     if (xQueueReceive(systemTasksMsgQueue, &msg, 100) == pdTRUE) {
       switch (msg) {
         case Messages::EnableSleeping:
-          // Make sure that exiting an app doesn't enable sleeping,
-          // if the exiting was caused by a firmware update
-          if (!bleController.IsFirmwareUpdating()) {
-            doNotGoToSleep = false;
-          }
+          wakeLocksHeld--;
           break;
         case Messages::DisableSleeping:
-          doNotGoToSleep = true;
+          GoToRunning();
+          wakeLocksHeld++;
           break;
         case Messages::GoToRunning:
-          // SPI doesn't go to sleep for always on mode
-          if (!settingsController.GetAlwaysOnDisplay()) {
-            spi.Wakeup();
-          }
-
-          // Double Tap needs the touch screen to be in normal mode
-          if (!settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::DoubleTap)) {
-            touchPanel.Wakeup();
-          }
-
-          spiNorFlash.Wakeup();
-
-          displayApp.PushMessage(Pinetime::Applications::Display::Messages::GoToRunning);
-          heartRateApp.PushMessage(Pinetime::Applications::HeartRateTask::Messages::WakeUp);
-
-          if (bleController.IsRadioEnabled() && !bleController.IsConnected()) {
-            nimbleController.RestartFastAdv();
-          }
-
-          state = SystemTaskState::Running;
+          GoToRunning();
           break;
         case Messages::TouchWakeUp: {
           if (touchHandler.ProcessTouchInfo(touchPanel.GetTouchInfo())) {
@@ -235,31 +213,23 @@ void SystemTask::Work() {
           break;
         }
         case Messages::GoToSleep:
-          if (doNotGoToSleep) {
-            break;
-          }
-          state = SystemTaskState::GoingToSleep; // Already set in PushMessage()
-          NRF_LOG_INFO("[systemtask] Going to sleep");
-          displayApp.PushMessage(Pinetime::Applications::Display::Messages::GoToSleep);
-          heartRateApp.PushMessage(Pinetime::Applications::HeartRateTask::Messages::GoToSleep);
+          GoToSleep();
           break;
         case Messages::OnNewTime:
-          if (alarmController.State() == Controllers::AlarmController::AlarmState::Set) {
+          if (alarmController.IsEnabled()) {
             alarmController.ScheduleAlarm();
           }
           break;
         case Messages::OnNewNotification:
           if (settingsController.GetNotificationStatus() == Pinetime::Controllers::Settings::Notification::On) {
-            if (state == SystemTaskState::Sleeping) {
+            if (IsSleeping()) {
               GoToRunning();
             }
             displayApp.PushMessage(Pinetime::Applications::Display::Messages::NewNotification);
           }
           break;
         case Messages::SetOffAlarm:
-          if (state == SystemTaskState::Sleeping) {
-            GoToRunning();
-          }
+          GoToRunning();
           displayApp.PushMessage(Pinetime::Applications::Display::Messages::AlarmTriggered);
           break;
         case Messages::BleConnected:
@@ -268,29 +238,25 @@ void SystemTask::Work() {
           bleDiscoveryTimer = 5;
           break;
         case Messages::BleFirmwareUpdateStarted:
-          doNotGoToSleep = true;
-          if (state == SystemTaskState::Sleeping) {
-            GoToRunning();
-          }
+          GoToRunning();
+          wakeLocksHeld++;
           displayApp.PushMessage(Pinetime::Applications::Display::Messages::BleFirmwareUpdateStarted);
           break;
         case Messages::BleFirmwareUpdateFinished:
           if (bleController.State() == Pinetime::Controllers::Ble::FirmwareUpdateStates::Validated) {
             NVIC_SystemReset();
           }
-          doNotGoToSleep = false;
+          wakeLocksHeld--;
           break;
         case Messages::StartFileTransfer:
           NRF_LOG_INFO("[systemtask] FS Started");
-          doNotGoToSleep = true;
-          if (state == SystemTaskState::Sleeping) {
-            GoToRunning();
-          }
+          GoToRunning();
+          wakeLocksHeld++;
           // TODO add intent of fs access icon or something
           break;
         case Messages::StopFileTransfer:
           NRF_LOG_INFO("[systemtask] FS Stopped");
-          doNotGoToSleep = false;
+          wakeLocksHeld--;
           // TODO add intent of fs access icon or something
           break;
         case Messages::OnTouchEvent:
@@ -318,6 +284,13 @@ void SystemTask::Work() {
           HandleButtonAction(action);
         } break;
         case Messages::OnDisplayTaskSleeping:
+          // The state was set to GoingToSleep when GoToSleep() was called
+          // If the state is no longer GoingToSleep, we have since transitioned back to Running
+          // In this case absorb the OnDisplayTaskSleeping
+          // as DisplayApp is about to receive GoToRunning
+          if (state != SystemTaskState::GoingToSleep) {
+            break;
+          }
           if (BootloaderVersion::IsValid()) {
             // First versions of the bootloader do not expose their version and cannot initialize the SPI NOR FLASH
             // if it's in sleep mode. Avoid bricked device by disabling sleep mode on these versions.
@@ -344,39 +317,23 @@ void SystemTask::Work() {
         case Messages::OnNewHour:
           using Pinetime::Controllers::AlarmController;
           if (settingsController.GetNotificationStatus() != Controllers::Settings::Notification::Sleep &&
-              settingsController.GetChimeOption() == Controllers::Settings::ChimesOption::Hours &&
-              alarmController.State() != AlarmController::AlarmState::Alerting) {
-            // if sleeping, we can't send a chime to displayApp yet (SPI flash switched off)
-            // request running first and repush the chime message
-            if (state == SystemTaskState::Sleeping) {
-              GoToRunning();
-              PushMessage(msg);
-            } else {
-              displayApp.PushMessage(Pinetime::Applications::Display::Messages::Chime);
-            }
+              settingsController.GetChimeOption() == Controllers::Settings::ChimesOption::Hours && !alarmController.IsAlerting()) {
+            GoToRunning();
+            displayApp.PushMessage(Pinetime::Applications::Display::Messages::Chime);
           }
           break;
         case Messages::OnNewHalfHour:
           using Pinetime::Controllers::AlarmController;
           if (settingsController.GetNotificationStatus() != Controllers::Settings::Notification::Sleep &&
-              settingsController.GetChimeOption() == Controllers::Settings::ChimesOption::HalfHours &&
-              alarmController.State() != AlarmController::AlarmState::Alerting) {
-            // if sleeping, we can't send a chime to displayApp yet (SPI flash switched off)
-            // request running first and repush the chime message
-            if (state == SystemTaskState::Sleeping) {
-              GoToRunning();
-              PushMessage(msg);
-            } else {
-              displayApp.PushMessage(Pinetime::Applications::Display::Messages::Chime);
-            }
+              settingsController.GetChimeOption() == Controllers::Settings::ChimesOption::HalfHours && !alarmController.IsAlerting()) {
+            GoToRunning();
+            displayApp.PushMessage(Pinetime::Applications::Display::Messages::Chime);
           }
           break;
         case Messages::OnChargingEvent:
           batteryController.ReadPowerState();
+          GoToRunning();
           displayApp.PushMessage(Applications::Display::Messages::OnChargingEvent);
-          if (state == SystemTaskState::Sleeping) {
-            GoToRunning();
-          }
           break;
         case Messages::MeasureBatteryTimerExpired:
           batteryController.MeasureVoltage();
@@ -385,9 +342,7 @@ void SystemTask::Work() {
           nimbleController.NotifyBatteryLevel(batteryController.PercentRemaining());
           break;
         case Messages::OnPairing:
-          if (state == SystemTaskState::Sleeping) {
-            GoToRunning();
-          }
+          GoToRunning();
           displayApp.PushMessage(Pinetime::Applications::Display::Messages::ShowPairingKey);
           break;
         case Messages::BleRadioEnableToggle:
@@ -422,14 +377,50 @@ void SystemTask::Work() {
 #pragma clang diagnostic pop
 }
 
-void SystemTask::UpdateMotion() {
-  if (state == SystemTaskState::GoingToSleep || state == SystemTaskState::WakingUp) {
+void SystemTask::GoToRunning() {
+  if (state == SystemTaskState::Running) {
     return;
   }
+  // SPI doesn't go to sleep for always on mode
+  if (!settingsController.GetAlwaysOnDisplay()) {
+    spi.Wakeup();
+  }
 
-  if (state == SystemTaskState::Sleeping && !(settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::RaiseWrist) ||
-                                              settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::Shake) ||
-                                              motionController.GetService()->IsMotionNotificationSubscribed())) {
+  // Double Tap needs the touch screen to be in normal mode
+  if (!settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::DoubleTap)) {
+    touchPanel.Wakeup();
+  }
+
+  spiNorFlash.Wakeup();
+
+  displayApp.PushMessage(Pinetime::Applications::Display::Messages::GoToRunning);
+  heartRateApp.PushMessage(Pinetime::Applications::HeartRateTask::Messages::WakeUp);
+
+  if (bleController.IsRadioEnabled() && !bleController.IsConnected()) {
+    nimbleController.RestartFastAdv();
+  }
+
+  state = SystemTaskState::Running;
+};
+
+void SystemTask::GoToSleep() {
+  if (IsSleeping()) {
+    return;
+  }
+  if (IsSleepDisabled()) {
+    return;
+  }
+  NRF_LOG_INFO("[systemtask] Going to sleep");
+  displayApp.PushMessage(Pinetime::Applications::Display::Messages::GoToSleep);
+  heartRateApp.PushMessage(Pinetime::Applications::HeartRateTask::Messages::GoToSleep);
+
+  state = SystemTaskState::GoingToSleep;
+};
+
+void SystemTask::UpdateMotion() {
+  if (IsSleeping() && !(settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::RaiseWrist) ||
+                        settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::Shake) ||
+                        motionController.GetService()->IsMotionNotificationSubscribed())) {
     return;
   }
 
@@ -452,7 +443,7 @@ void SystemTask::UpdateMotion() {
   }
   if (settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::LowerWrist) && state == SystemTaskState::Running &&
       motionController.ShouldLowerSleep()) {
-    PushMessage(Messages::GoToSleep);
+    GoToSleep();
   }
 }
 
@@ -468,7 +459,7 @@ void SystemTask::HandleButtonAction(Controllers::ButtonActions action) {
   switch (action) {
     case Actions::Click:
       // If the first action after fast wakeup is a click, it should be ignored.
-      if (!fastWakeUpDone && state != SystemTaskState::GoingToSleep) {
+      if (!fastWakeUpDone) {
         displayApp.PushMessage(Applications::Display::Messages::ButtonPushed);
       }
       break;
@@ -488,17 +479,10 @@ void SystemTask::HandleButtonAction(Controllers::ButtonActions action) {
   fastWakeUpDone = false;
 }
 
-void SystemTask::GoToRunning() {
-  if (state == SystemTaskState::Sleeping) {
-    state = SystemTaskState::WakingUp;
-    PushMessage(Messages::GoToRunning);
-  }
-}
-
 void SystemTask::OnTouchEvent() {
   if (state == SystemTaskState::Running) {
     PushMessage(Messages::OnTouchEvent);
-  } else if (state == SystemTaskState::Sleeping) {
+  } else {
     if (settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::SingleTap) or
         settingsController.isWakeUpModeOn(Pinetime::Controllers::Settings::WakeUpMode::DoubleTap)) {
       PushMessage(Messages::TouchWakeUp);
@@ -507,10 +491,6 @@ void SystemTask::OnTouchEvent() {
 }
 
 void SystemTask::PushMessage(System::Messages msg) {
-  if (msg == Messages::GoToSleep && !doNotGoToSleep) {
-    state = SystemTaskState::GoingToSleep;
-  }
-
   if (in_isr()) {
     BaseType_t xHigherPriorityTaskWoken = pdFALSE;
     xQueueSendFromISR(systemTasksMsgQueue, &msg, &xHigherPriorityTaskWoken);

src/systemtask/SystemTask.h

@@ -52,7 +52,7 @@ namespace Pinetime {
   namespace System {
     class SystemTask {
     public:
-      enum class SystemTaskState { Sleeping, Running, GoingToSleep, WakingUp };
+      enum class SystemTaskState { Sleeping, Running, GoingToSleep };
       SystemTask(Drivers::SpiMaster& spi,
                  Pinetime::Drivers::SpiNorFlash& spiNorFlash,
                  Drivers::TwiMaster& twiMaster,
@@ -79,11 +79,8 @@ namespace Pinetime {
 
       void OnTouchEvent();
 
-      void OnIdle();
-      void OnDim();
-
       bool IsSleepDisabled() {
-        return doNotGoToSleep;
+        return wakeLocksHeld > 0;
       }
 
       Pinetime::Controllers::NimbleController& nimble() {
@@ -91,7 +88,7 @@ namespace Pinetime {
       };
 
       bool IsSleeping() const {
-        return state == SystemTaskState::Sleeping || state == SystemTaskState::WakingUp;
+        return state != SystemTaskState::Running;
       }
 
     private:
@@ -127,13 +124,14 @@ namespace Pinetime {
       bool isBleDiscoveryTimerRunning = false;
       uint8_t bleDiscoveryTimer = 0;
       TimerHandle_t measureBatteryTimer;
-      bool doNotGoToSleep = false;
+      uint8_t wakeLocksHeld = 0;
       SystemTaskState state = SystemTaskState::Running;
 
       void HandleButtonAction(Controllers::ButtonActions action);
       bool fastWakeUpDone = false;
 
       void GoToRunning();
+      void GoToSleep();
       void UpdateMotion();
       bool stepCounterMustBeReset = false;
       static constexpr TickType_t batteryMeasurementPeriod = pdMS_TO_TICKS(10 * 60 * 1000);

src/systemtask/WakeLock.cpp

@@ -0,0 +1,27 @@
+#include "systemtask/WakeLock.h"
+
+using namespace Pinetime::System;
+
+WakeLock::WakeLock(SystemTask& systemTask) : systemTask {systemTask} {
+  lockHeld = false;
+}
+
+WakeLock::~WakeLock() {
+  Release();
+}
+
+void WakeLock::Lock() {
+  if (lockHeld) {
+    return;
+  }
+  systemTask.PushMessage(Messages::DisableSleeping);
+  lockHeld = true;
+}
+
+void WakeLock::Release() {
+  if (!lockHeld) {
+    return;
+  }
+  systemTask.PushMessage(Messages::EnableSleeping);
+  lockHeld = false;
+}

src/systemtask/WakeLock.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "systemtask/SystemTask.h"
+
+namespace Pinetime {
+  namespace System {
+    class WakeLock {
+    public:
+      WakeLock(SystemTask& systemTask);
+      ~WakeLock();
+      void Lock();
+      void Release();
+
+    private:
+      bool lockHeld;
+      SystemTask& systemTask;
+    };
+  }
+}