44 lines
3.3 KiB
Markdown
44 lines
3.3 KiB
Markdown
# Introduction to the code
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This page is meant to guide you through the source code, so you can find the relevant files for what you're working on.
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## FreeRTOS
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Infinitime is based on FreeRTOS, a real-time operating system.
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FreeRTOS provides several quality of life abstractions (for example easy software timers)
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and most importantly supports multiple tasks.
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If you want to read up on real-time operating systems, you can look [here](https://www.freertos.org/implementation/a00002.html) and [here](https://www.freertos.org/features.html).
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The main "process" creates at least one task and then starts the FreeRTOS task scheduler.
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This main "process" is the standard main() function inside [main.cpp](/src/main.cpp).
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The task scheduler is responsible for giving every task enough cpu time.
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As there is only one core on the SoC of the PineTime, real concurrency is impossible and the scheduler has to swap tasks in and out to emulate it.
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### Tasks
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Tasks are created by calling `xTaskCreate` and passing a function with the signature `void functionName(void*)`.
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For more info on task creation see the [FreeRTOS Documentation](https://www.freertos.org/a00125.html).
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In our case, main calls `systemTask.Start()`, which creates the **"MAIN" task**.
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The function running inside that task is `SystemTask::Work()`.
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You may also see this task being referred to as the **work task**.
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Both functions are located inside [systemtask/SystemTask.cpp](/src/systemtask/SystemTask.cpp). `SystemTask::Work()` initializes all the driver and controller objects.
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It also starts the **task "displayapp"**, which is responsible for launching and running apps, controlling the screen and handling touch events (or forwarding them to the active app).
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You can find the "displayapp" task inside [displayapp/DisplayApp.cpp](/src/displayapp/DisplayApp.cpp).
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There are also other tasks that are responsible for Bluetooth ("ll" and "ble" inside [libs/mynewt-nimble/porting/npl/freertos/src/nimble_port_freertos.c](/src/libs/mynewt-nimble/porting/npl/freertos/src/nimble_port_freertos.c))
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and periodic tasks like heartrate measurements ([heartratetask/HeartRateTask.cpp](/src/heartratetask/HeartRateTask.cpp)).
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While it is possible for you to create your own task when you need it, it is recommended to just add functionality to `SystemTask::Work()` if possible.
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If you absolutely need to create another task, try to estimate how much [stack space](https://www.freertos.org/FAQMem.html#StackSize) (in words/4-byte packets)
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it will need instead of just typing in a large-ish number.
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You can use `configMINIMAL_STACK_SIZE` which is currently set to 120 words.
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## Controllers
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Controllers in InfiniTime are singleton objects that can provide access to certain resources to apps.
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Some of them interface with drivers, others are the driver for the resource.
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The resources provided don't have to be hardware-based.
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They are declared in main.cpp and initialized in [systemtask/SystemTask.cpp](/src/systemtask/SystemTask.cpp).
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Some controllers can be passed by reference to apps that need access to the resource (for example vibration motor).
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They reside in [components/](/src/components/) inside their own subfolder.
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## Apps
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For more detail see the [Apps page](./Apps.md)
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## Bluetooth
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Header files with short documentation for the functions are inside [libs/mynewt-nimble/nimble/host/include/host/](/src/libs/mynewt-nimble/nimble/host/include/host/).
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