Blackmagic Probe Autodetection Picks UART

[glingy]

Configuration

Operating system: macOS Catalina 10.15.7

PlatformIO Version (platformio --version): PlatformIO, version 5.0.3

Description of problem

MacOS auto-detects incorrect serial port for black magic probe. On macOS, the serial ports are labeled by the descriptor index: /dev/cu.usbmodemXXXXXXX# where XXXXXX is the serial port identifier provided by the usb device and # is the interface descriptor id. I do not know if there is a better way of distinguishing these, my computer shows None for serial.tools.list_parts.ListPartInfo.interface, but my computer does recognize the interface name:
Adding a condition for macOS to filter by the interface descriptor id seems to be more reliable than searching for "GDB" in the usb description which will always be the same for both ports. For context, printing item on line 140 of builder/tools/pioupload.py shows:

{'port': '/dev/cu.usbmodem5596E0E13', 'description': 'Black Magic Probe (STLINK/V2) v1.7.1-194-g8089e05-dirty', 'hwid': 'USB VID:PID=1D50:6018 LOCATION=20-2'}
{'port': '/dev/cu.usbmodem5596E0E11', 'description': 'Black Magic Probe (STLINK/V2) v1.7.1-194-g8089e05-dirty', 'hwid': 'USB VID:PID=1D50:6018 LOCATION=20-2'}

So identifying by usb description is not working. The usb descriptor id is a constant in the blackmagic probe firmware, and should be a good option to filter on for auto-detection unless the descriptors change in a new release of that firmware.

Steps to Reproduce

1. Plug in a BMP (I'm using a blue pill clone, but should be the same with a real one)
2. Create any new project with the blackmagic debugger and attempt to download using it without specifying upload_port
3. It hangs on upload because it's trying to use the uart port for gdb.
4. Specify the upload_port, and it works

Additional info

I'm working on making a PR and testing linux because I'm curious if there's a difference there. According to the pyserial docs: https://pyserial.readthedocs.io/en/latest/tools.html#serial.tools.list_ports.ListPortInfo it should always give the usb descriptor, not the individual interface descriptors for that "description" field in which case GDB filtering may have been broken on all non-windows platforms for a while.

[glingy]

Potential fix for macOS if this is reproducible and not just my computer:
line 140 of builder/tools/pioupload.py

if IS_MACOS and port.startswith("/dev/cu.usbmodem") and port.endswith("1"):
    return port

[glingy]

After testing on linux, ubuntu 20.04.2 returns "Black Magic Probe (STLINK/V2) v1.7.1-194-g8089e05-dirty - Black Magic UART Port" and "Black Magic Probe (STLINK/V2) v1.7.1-194-g8089e05-dirty - Black Magic GDB Port" for the description field, so filtering by "GDB" seems to work fine there.

[glingy]

Note: I was able to test and received the same issue on Windows where it consistently picked COM4, but GDB was COM3. I'm not super familiar with Windows COM port ordering, but it seems to also be related to the usb interface descriptor number in some way. I'm not sure this is a great solution, but filtering by one digit in the hwid line (0 or 2) or guessing the first COM port instead of the second might be better options. I'm going to keep testing and make a fork with what I find

[ivankravets]

Does it work if you specify debug_port manually using https://docs.platformio.org/en/latest/projectconf/section_env_debug.html#debug-port ?

You can also manually control upload_port https://docs.platformio.org/en/latest/projectconf/section_env_upload.html#upload-port

[jcw]

FWIW, I've always had to specify the exact ports, and then things work fine.
And yes, the GDB is always the one ending in "1" and the console port always ends in "3" (by design).
Both upload and monitor could benefit (when there is only 1 BMP attached) if they knew about this convention.

[glingy]

I completely missed notifications from this, evidently I need to fix that. Yes, it works if I manually specify the ports on all platforms. However, especially on windows since there is no difference in Device Manager between the GDB and UART ports, it's a guessing game and as a side issue that I probably should submit separately with blackmagic it seems to lock up when you accidentally use the uart port as GDB, so if you guess wrong you have to unplug it and plug it in again and hope it uses the same COM ports so you know which is which now.

[ivankravets]

Thanks for the report! Could you re-test with pio upgrade --dev? Does it find a port properly?

[jcw]

On MacOS, I can now omit monitor_port (terrific!), but I still have to specify upload_port:

$ pio run -t upload -e jnzero-echo
Processing jnzero-echo (board: nucleo_l053r8; platform: ststm32; framework: cmsis)
[...]
AVAILABLE: blackmagic, cmsis-dap, jlink, mbed, stlink
CURRENT: upload_protocol = blackmagic
Looking for BlackMagic port...
Auto-detected: /dev/cu.usbmodemDFE3C8B13
Uploading .pio/build/jnzero-echo/firmware.elf
[...]

As you can see, it picked the xxx3 port for uploading, which then hangs.

[ivankravets]

Fixed. Could you re-run pio upgrade --dev. Does it work well for uploading, debugging, and device monitoring?

[jcw]

Yep, latest now works for upload and monitor - i.e. port specs not needed when a single BMP is present \o/
(I'm not set up for debugging, can't check that right now)