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README.md

Firmware

The firmware is written in Rust. It can be used either bare metal or with a bootloader.

Flashing without a bootloader

  • Connect RX/TX of your uart/usb-adapter to PA9/PA8.
  • Put the STM32 into download mode by setting BOOT0 high and resetting.
  • cd firmware
  • make flash.bare.release (assuming that ttyUSB0 is your uart adapter)

Flashing and using a bootloader

Preparing the bootloader

Building with the --features=bootloader flag enabled will relocate the program entry point to FLASH + 0x2000, allowing to use a bootloader.

Follow these steps in order to build and initially flash the bootloader. You only need to perform this once.

Flashing the firmware

Bootloader mode can be entered by sending the sboot/bootloader.syx sysex to the zeroth output of the midikraken (e.g. using amidi -p hw:1,0,0 -s bootloader.syx).

If that does not work (e.g. because the firmware is not present or corrupt), pull PB12 low and reset.

  • Connect the Midikraken to USB
  • (in case of a defective firmware, pull PB12 low and reset)
  • cd firmware
  • make flash.dfu.release (will send the reset sysex automatically)

Debugging

printf-debugging can be seen on PA9/PA10 with 38400 baud. In the default configuration, you should see only

========================================================
midikraken @ 6b3d42c5bf369a8da5d348a39342b91c2a3f7e80
      built on 2021-04-09T18:50:50.306707469+00:00
========================================================

You can enable more debug information with the debugprint flag.

Note that this degrades performance close to being unusable.

Benchmarking

The software UART timer interrupt fires 93750x per second. This leaves only 768 cpu cycles per call to the ISR.

To measure the performance of the software UART in the worst-case scenario (all receivers are receiving their last bit and thus are finishing, and all senders fetch their next byte and start transmitting it), enable the benchmark feature flag. Note that this will send and receive garbage data.