Development environment

There are three main components to the development environment/tolchain.

1. ARM compiler. The gcc compiler should be accessible via the arm-none-eabi-gcc command.
2. GDB Client. This is the GDB client interface you will be interacting with. Direclty via the command line or indirectly with vscode or some other GDB UI wrapper
3. GDB Server. In my case OpenOCD. This is the thing that will handle all interaction with the STM32.

ARM Compiler

I got the official arm toolchain from https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads. Then just unzip and add the bin directory the the PATH in your .bashrc. I chose to install in the /opt directory. If you're not able to run the Makefile after installing the comiler, consult the interwebs

GDB client

This should be installed with the arm toolchain. I'm using the vscode extension 'cortex-debug' by Marus25. to integrate with vscode.

To run the GDB client from the command line, invoke with arm-none-eabi-gdb then connect to GDB server target remote 192.168.0.30:3333. Then yu can load and run a program by

(gdb) file <client side elf file>
(gdb) monitor reset halt
(gdb) monitor flash protect 0 0 15 off
(gdb) monitor stm32f0x mass_erase 0
(gdb) monitor flash write_image /tmp/executable.elf
(gdb) monitor reset halt

GDB Server (OpenOCD)

The last component to this toolchain is openocd. OpenOCD can communicate with the STLink to access the microcontroller over the SWD(?) interface. It can also recieve commands from a GDB client.

The GDB server needs to be running before you can connect via the client and do anything else. To run the OpenOCD, use this command. openocd -f /usr/local/share/openocd/scripts/interface/stlink.cfg -f /usr/local/share/openocd/scripts/target/stm32f0x.cfg -f /usr/local/share/openocd/scripts/test.cfg -c "init" My test.cfg file contains 'bindto 0.0.0.0'. Not sure why that is. I think it let's me access the GDB port from another machine.

My setup

I use a raspberry pi as a "host PC" for my STM32. So the rpi has the STLink connected via USB and hardware attached to that. The RPI also runs OpenOCD. Then VSCode, the ARM compiler, and GDB Client all run on my laptop. The 'beggining' of my workflow is to run make in my vscode terminal. Then F5 will call start cortex-debug with .vscode/launch.json. I've customized this configuration to copy the elf file over ssh to the rpi, then call the correct GDB commands to flash the STM32.

Debugging

Recover from SWD lockout

openOCD shows Error: init mode failed (unable to connect to the target). This could be caused by flashing a program that reconfigures the SWD GPIOs to something else. Then ST-Link cannot reach host. To fix, I connect ST-Link to laptop and launch STM32CubeProgrammer. Connect NRST (pin 7) to GND. Click 'connect' and remove the NRST from GND moments after. It should connect and allow you to use the erase all flash memory utilty.