WeAct Studio Blackpill and USB USART

[TaurusEight]

The README.md in ./src/platforms/common/blackpill-f4 states that UART TX is pin PA2 and UART RX is pin PA3. However, the Blackpill documentation from WeAct Studio shows that the USB D- pin connects to PA11 and the D+ pin connects to PA12.

Shouldn't the Blackmagic firmware use pins PA11 and PA12?

Link to the Blackpill information page from WeAct Studio: https://stm32-base.org/boards/STM32F411CEU6-WeAct-Black-Pill-V2.0.html

[dragonmux]

UART is not USB - BMD does indeed use D+ and D- for USB which is an entirely different protocol to UART. Pins PA2 and 3 are used for the target UART interface which we then translate and present up to the host over USB as the aux serial interface.

https://github.com/WeActStudio/WeActStudio.MiniSTM32F4x1 for their official pinouts and documentation which helpfully includes a diagram showing what peripherals can be routed out to which pins with pin function alt modes. PA2/3 are listed as {R,T}X2 there in a light blue box.

[TaurusEight]

Thank you.

[TaurusEight]

Under Linux, which device is the aux serial interface? The BMP shows up as /dev/ttyACM0 and /dev/ttyACM1, with symbolic links. My understanding is that both the SWD interface and the aux serial interface can be used at the same time. Is there more detailed documentation on the use of this aux interface under Linux that I'm overlooking?

[dragonmux]

Use the project's udev rules. They fix the permissions so you do not use sudo to access any part of the firmware, and they provide stable names - /dev/ttyBmpGdb and /dev/ttyBmpTarg (+ ones with the serial number after) - these are, respectively, the GDB interface and aux serial interface.

We cannot ever predict the ordering of the /dev/ttyACMn names because they're enumeration order dependant, and this is unstable and unpredictable.

[TaurusEight]

/dev/ttyBmpTarg is the aux serial interface accessed through the Blackmagic Probe. Thank you. That is the information I wished to confirm. Those names are symbolic links to /dev/ttyACM0 and /dev/ttyACM1.