- A cross-compiler : [ARM-GCC (10.3-2021.10)](https://developer.arm.com/downloads/-/gnu-rm)
- The NRF52 SDK 15.3.0 : [nRF-SDK v15.3.0](https://developer.nordicsemi.com/nRF5_SDK/nRF5_SDK_v15.x.x/nRF5_SDK_15.3.0_59ac345.zip)
- The Python 3 modules `cbor`, `intelhex`, `click` and `cryptography` modules for the `mcuboot` tool (see [requirements.txt](../tools/mcuboot/requirements.txt))
- To keep the system clean, you can install python modules into a python virtual environment (`venv`)
**BUILD_RESOURCES (\*\*)**| Generate external resource while building (needs [lv_font_conv](https://github.com/lvgl/lv_font_conv) and [lv_img_conv](https://github.com/lvgl/lv_img_conv). |`-DBUILD_RESOURCES=1`
By default, this variable is set to *Release*. It compiles the code with size and speed optimizations. We use this value for all the binaries we publish when we [release](https://github.com/InfiniTimeOrg/InfiniTime/releases) new versions of InfiniTime.
The *Debug* mode disables all optimizations, which makes the code easier to debug. However, the binary size will likely be too big to fit in the internal flash memory. If you want to build and debug a *Debug* binary, you'll need to disable some parts of the code. For example, the icons for the **Navigation** app use a lot of memory space. You can comment the content of `m_iconMap` in the [Navigation](https://github.com/InfiniTimeOrg/InfiniTime/blob/develop/src/displayapp/screens/Navigation.h#L148) application to free some memory.
DFU files are the files you'll need to install your build of InfiniTime using OTA (over-the-air) mechanism. To generate the DFU file, the Python tool [adafruit-nrfutil](https://github.com/adafruit/Adafruit_nRF52_nrfutil) is needed on your system. Check that this tool is properly installed before enabling this option.
If you just want to build the project and run it on the Pinetime, using *pinetime-app* is recommended. See [this page](../bootloader/README.md) for more info about bootloader support.