I’ve been using the STM32F4 Discovery board for prototyping SmartMic. This board has an ancillary STMF103 ARM3 (U2) that is used to debug the STM32F4 via the ST-LINK interface, which allows me to use gdb, flash the STM32F4 and support semi-hosting for development.
I want to use this same ARM3 to debug SmartMic, i.e. use the Discovery board as a STLINK “pod” for custom STM32F4 designs. To test this idea I used the ARM3 on one Discovery board to debug a STM32F4 on a second Discovery board. It worked quite well, here’s how I did it:
1. Remove CN3 jumpers from both Discovery boards.
2. Make the following connections:
|Signal||Host Discovery CN2||STM32F4 Under Test|
Note just three wires are required, so a little bit simpler than JTAG. I added one extra wire to allow the Host Discovery to supply 5V power to the DUT.