Using a Blue Pill as a Black Magic Probe - The Easy Way

The Right Kind of Blue Pill

To fit the software in flash you require a 128K Blue Pill rather than the 64K variety.

From my rather confused and stumbling research, the 128K variety are far more common now and you may have to struggle to find a 64K version.

Any clarification of the 64K / 128K issue would be more than welcome.

Obtaining the firmware

The Black Magic Probe project is hosted at: github.com/blacksphere/blackmagic and you can obtain the firmware with: 

git clone git@github.com:blacksphere/blackmagic.git
cd blackmagic

At the time of writing, the current release is v1.7.1, but you can substitute this with the current release in your time-stream by checking github.com/blacksphere/blackmagic/tags 

git checkout v1.7.1

Build the Firmware

You'll find many instructions online saying use the stlink target and this does, indeed, work. But if you do use this target, the onboard LED doesn't work and the wires you need to connect to the target device will be an arbitrary collection of GPIOs.

If you use the swlink target, the LED works and the SWD pins are the SWD pins and the JTAG pins are the JTAG pins and any need for funny adapter boards just disappears.

As well as arm-none-eabi-gcc, you'll need libnewlib-arm-none-eabi installed. 

make clean && make PROBE_HOST=swlink

Prepare to Upload

Move the BOOT0 jumper from 0 to 1 to use the serial flasher boot loader.

Connect a USB/serial adaptor to the Blue Pill:

USB/Serial Blue Pill
3V3 3V3
GND GND
RX A9(TX1)
TX A10(RX1)

Insert the USB/serial adapter in your computer.

Upload the Firmware

I'm using stm32flash to do my serial uploads.

I didn't want to bother using the DFU option to upgrade my firmware in the future and I made the mistake of skipping uploading the DFU bootloader. But, even if you plan to never use DFU, you still need the bootloader to make the Blue Pill enumerate it's USB ports! 

stm32flash -o /dev/ttyUSB0
stm32flash -w src/blackmagic_dfu.bin -v /dev/ttyUSB0
stm32flash -w src/blackmagic.bin -v -S 0x08002000 /dev/ttyUSB0

I'm not sure if the stm32flash -o option is actually required (I'm a newbie myself) but it doesn't do any particular harm.

Try it Out

Unplug and disconnect the USB/serial adaptor, put the BOOT0 jumper back on 0, and re connect the new Black Magic Probe via USB.

Trying ls /dev/tty* should show up /dev/ttyACM0 and /dev/ttyACM1.

Unplug it and try connecting a second "pill" to the SWD port.

The following should now give the expected results.

gdb-multiarch
target extended-remote /dev/ttyACM0
monitor swdp
attach 1
info registers
quit

Flashing script

We can use the BMP to flash an STM-32 dev board with this script

We're done

Right I'm off to try and learn how to debug embedded Rust. And you're off to do whatever it is you need to do... See you soon, maybe.

Hang on, What about JTAG?

Well, I'm not quite ready for JTAG just yet. But, with an extra header for the other 3 JTAG pins, it shouldn't be a problem.

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