Sapog - advanced multiplatform ESC firmware
C C++ Other
Latest commit 3e6cad8 Dec 23, 2016 @pavel-kirienko pavel-kirienko committed on GitHub Merge pull request #21 from eyeam3/bootloader_hw_ver_fix
Get hardware version from GPIOs in bootloader

PX4 Sapog

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Please refer to the documentation page at


If you're not running Linux or OSX natively, you can download Bistromathic - a Linux virtual machine pre-configured for embedded development.


The bootloader allows to update the firmware via the standard UAVCAN firmware upgrade protocol, which is documented at No additional steps are needed to build the bootloader - the build system will build it automatically together with the firmware. The resulting *.elf file will be extended with the bootloader too, so it can be flashed directly into an factory fresh MCU.

Build instructions

Prebuilt binaries are available at


  • GCC ARM 4.9 or newer (beware that some newer versions of GCC segfault during linking)
  • Python 3.2+
  • Linux or OSX host computer (Windows is not supported)
git submodule update --init --recursive
cd firmware
make RELEASE=1 # RELEASE is optional; omit to build the debug version

The build outputs will be stored into build/:

  • *.application.bin - built application binary, suitable for uploading via the bootloader;
  • *.compound.bin - application binary together with the bootloader, in one image;
  • compound.elf - application ELF together with the bootloader, in one file; this option is recommended for debugging.

Execute ./ [portname] from the tools directory to flash the firmware with a Black Magic Debug Probe.


We recommend Eclipse for IDE, but any other IDE will work equally well. If you prefer Eclipse and need GUI debugging, avoid upgrading to any version newer than Luna, since in newer releases GUI GDB debugging of embedded targets is broken. Otherwise we recommend to use the latest Eclipse together with CLI GDB client. It's inconvenient, but unlike Eclipse it works reliably.

When editing code, please follow the PX4 coding conventions.

Hardware timer usage

  • TIM1 - 3-phase FET bridge PWM
  • TIM2 - ADC synchronization, works in lockstep with TIM1
  • TIM4 - Hard real time callout interface for motor control logic (preempts the kernel)
  • TIM5 - RC PWM input capture
  • TIM6 - High precision timestamping for motor control logic (sub-microsecond resolution, never overflows)
  • TIM7 - General purpose timestamping


Reference hardware design is published under CC BY-SA 3.0 in the PX4 Hardware repository.

Known commercially available compatible hardware designs are listed below.