Firmware for the Black Magic Debug Probe.

The Black Magic Probe is a modern, in-application debugging tool for embedded microprocessors. It allows you see what is going on 'inside' an application running on an embedded microprocessor while it executes. It is able to control and examine the state of the target microprocessor using a JTAG or Serial Wire Debugging (SWD) port and on-chip debug logic provided by the microprocessor. The probe connects to a host computer using a standard USB interface. The user is able to control exactly what happens using the GNU source level debugging software, GDB.

See online documentation at https://github.com/blacksphere/blackmagic/wiki