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README_SWD.md

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Debugging / Flashing an SWD-capable microcontroller via the Pi

Wiring:

SWCLK -- Broadcom GPIO25
SWDIO -- Broadcom GPIO24
RESET -- not used
GND   -- any
VCC   -- any 3V3 (for STM32 at least, I think)

Setting the target chip

Only needs to be done one-time unless chip changes.

Get list of available targets:

ssh [email protected] ls -lah /usr/share/openocd/scripts/target/stm32*.cfg

Point the config file to a specific chip:

ssh [email protected] sudo ln -sf /usr/share/openocd/scripts/target/stm32h7x.cfg /opt/openocd/chip.cfg

Start debugging

Connect wires, then run:

ssh [email protected] sudo systemctl start openocd.service

Now, on your local machine, you can connect a local instance of gdb-multilib:

gdb-multilib
(gdb) target extended-remote 10.0.0.1:3333
(gdb) monitor reset

You will need these prerequisites:

apt install binutils-multilib gdb-multilib

integration in VSCode

Install the Cortex-Debug extension.

Use this .vscode/launch.json configuration (change executable of course, and compile with debug symbols on and optimisations off):

{
    // Use IntelliSense to learn about possible Node.js debug attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "cwd": "${workspaceRoot}",
            "executable": "obj/main/betaflight_STM32H743.elf",
            "name": "Cortex OpenOCD",
            "request": "launch",
            "type": "cortex-debug",
            "servertype": "external",
            "gdbTarget": "10.0.0.1:3333",
            "runToEntryPoint": "main",
            "showDevDebugOutput": "none",
            "objdumpPath": "/usr/bin/objdump"
        }
    ]
}

Add this line to settings .vscode/launch.json configuration:

    "cortex-debug.gdbPath.linux": "/usr/bin/gdb-multiarch"

Flashing

  1. Get an .elf binary onto the pi, using e.g. sftp or rsync
  2. Make sure the debugger is stopped ssh [email protected] sudo systemctl stop openocd.service
  3. Flash ssh [email protected] 'openocd -f /opt/openocd/openocd.cfg -c "program betaflight_STM32H743.elf verify reset exit"'