The Raspberry Pi Pico's RP2040 microcontroller keeps popping up in all manner of new boards. From tiny boards to full blown electronics suites. The reasons are largely due to its easy of use and plentiful stock. The latest surprise board to feature the powerful microcontroller comes from Raspberry Pi itself. The $12 Raspberry Pi Debug Probe is a hardware debug solution for Arm-based microcontrollers, that includes our favorite microcontroller. The board may not be a candidate for our list of best RP2040 boards, but for those that need it, it will be invaluable.
Raspberry Pi's Debug Probe is essentially a means to monitor the output and debug code running on a bare metal board. In programming we would normally have a debugger running and this would flag any issues as they occur. But as Eben Upton explains in the launch blog post, "But what if your C program is running directly on the processor, without an operating system (this is often referred to as bare metal operation)? What if you’re writing an operating system? In this case, you’ll need a way to access the debug capabilities built into the processor itself. And that’s where a debug probe comes in."
The Raspberry Pi Debug Probe can be used with a Raspberry Pi Pico or any Arm based microcontroller with 3.3 Volt I/O and a SWD (Serial Wire Debug) port. The Raspberry Pi Pico and the Raspberry Pi Pico W have these pins exposed on the top of the PCB (the Raspberry Pi Pico H and WH have a three pin JST SWD port pre-soldered). Connecting these pins to the Debug Probe enables the probe to watch for bugs. The probe then connects to a computer via USB, providing a USB to serial interface. using software which follows the CMSIS-DAP, a protocol that Arm standardized, users can step through their code with their favorite software debug platform.
Since its launch, the Raspberry Pi Pico has been able to act as a Picoprobe, but the steps to achieve this involved a few messy wires. The $12 Debug Probe provides a low wire solution in a delightfully neat package.