OpenTX 2.3 fork for various fixes for Turnigy 9XR Pro

Fixed issues

• RTC not working. #7421
• 4-in-1 multimodule menu not working. #8946
• 4-in-1 multimodule telemetry not working due to missing inversion. #8954.
• FlySky AFHDS2A frequent "telemetry lost" & "telemetry recovered" warnings on Moblite7 when disarmed. (Too small TELEMETRY_TIMEOUT10ms.) (This issue is actually most likely a problem in Betaflight's Flysky SPI driver, not a problem with OpenTX.)
• Trainer port not working #8977. Works in OpenTX 2.3.7, but not in 2.3.15.
  • First bad commit is 697184a517b977c7183db01962479bb09e75ecc8

To be fixed issues

• Audio playback often fails and requires restart to recover.
  • There might be some issues with SD card reading.
  • This does not appear to be due to WD crash.
• Occasional crash when changing models. #7772.
  • Changing to and from a model that has External RF MULTI enabled causes this. Models with external RF OFF do not crash.
  • Crashes often when turning radio on and changing from one MULTI model to another MULTI model.
  • Longer watchdog timeout does not prevent crashes, even with 5s WD timeout.
  • Crashes seem to happen in EEPROM code.
  • Crashes seem to happen during eepromWaitTransferComplete(). The IRQ never fires.
  • Unable to get it to crash on 2.3.7
  • Bisection:
    • Last non-crashing commit: 860b50faa (2.3.11)
    • First crashing commit: 78dd51606 (2.3.12)
    • Inbetween commits don't build.
• Sometimes the radio crashes on startup and there's no splash screen and no audio.
• Radio hangs on startup splash screen occasionally.
• Radio hangs on shutdown splash screen occasionally.
• Companion shuts down when closing a model editor window. (Not 9XR Pro specific.)
• Companion messes up input channel sources.
  • Input sources change to ???. Switches change to P1, P2 or P3. MAX might change to CYC1.

NOTE: On an unexpected shutdown, sdInit() is not called. Then audio does not work. This is expected behaviour. (Although maybe it should fallback to tone generator?).

Build instructions

There are complete build instructions for OpenTX here: Step-by-step-guide-to-building-%28custom%29-OpenTX-firmware-under-Ubuntu-Linux.

For building just the firmware under either plain Linux (Ubuntu) or WSL in windows, first install the build tools by running the following commands:

# Install necessary tools and libraries
sudo apt install build-essential cmake gcc lib32z1

# Install the correct ARM GCC tools. 
wget https://launchpad.net/gcc-arm-embedded/4.7/4.7-2013-q3-update/+download/gcc-arm-none-eabi-4_7-2013q3-20130916-linux.tar.bz2
tar xjf gcc-arm-none-eabi-4_7-2013q3-20130916-linux.tar.bz2
rm gcc-arm-none-eabi-4_7-2013q3-20130916-linux.tar.bz2
sudo mv gcc-arm-none-eabi-4_7-2013q3 /opt/gcc-arm-none-eabi

Then run the rebuild.sh script from this repo to build 9XRPRO firmware under build-stuff directory.

Docker builds

• pfeerick's fork
• Original docker build project