How to fix PlatformIO “Start debugging” doing nothing


When you click on Start debugging, press F5 or click on the debug start triangle in PlatformIO

the firmware builds but then nothing happens:

Linking .pio/build/olimex_e407/firmware.elf
Checking size .pio/build/olimex_e407/firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [          ]   0.7% (used 936 bytes from 131072 bytes)
Flash: [          ]   1.7% (used 18064 bytes from 1048576 bytes)
Building .pio/build/olimex_e407/firmware.bin
======================================================================== [SUCCESS] Took 2.72 seconds ========================================================================


You need to specify a debug_tool in platformio.ini. For STM32 processors, a typical choice is

debug_tool = stlink

A list of options for debug_tool is available here.

Note that you can NOT debug many boards via the USB port. You can not debug boards attached via serial-to-USB converter (like many Arduino boards). Your board need to have a proper debugger on-board (like an stlink which is integrated on many STM32 eval boards) or you need to use an external debugger.