The picoLemon MultiProbe Pico Debugger Lets You Target Four SWD Devices at the Same Time
Why debug one by one, when you can target four devices-under-test simultaneously?
Pseudonymous maker "picoLemon" has built a development board designed to ease working with multiple Raspberry Pi RP2040 and RP2350 microcontrollers — delivering simultaneous debugging across four Serial Wire Debug (SWD) ports: the MultiProbe Pico Debugger.
"[The] MultiProbe Pico Debugger [is] a development board to debug multiple [Raspberry Pi] Pico devices, based on the official Debug Probe," picoLemon explains of the tool. "Any RP2040 or RP2350 device can [also] be used, see [the schematics] for the GPIO [General-Purpose Input/Output pin] assignments or order a PCB from your favorite PCB supplier."
The board itself is inspired by the Raspberry Pi Debug Probe, a Serial Wire Debug (SWD) tool released back in February 2023 and primarily built with the Raspberry Pi Pico family in mind as the device under test. In addition to the dedicated debug board, Raspberry Pi also released a firmware to convert any Raspberry Pi Pico development board into a Debug Probe — something picoLemon also supports for the fourfold-enlarged MultiProbe Pico Debugger.
The MultiProbe provides four active SWD ports on a single USB connection, its creator claims, allowing for four devices under test to be targeted simultaneously. There are also four UART serial buses, though these are multiplexed to two communication ports — and indicator LEDs let you see exactly which port is active. There's support for using the debugger in Linux, Apple's macOS, and Microsoft's Windows, though picoLemon warns the latter requires a driver workaround and is not officially supported at the time of writing.
"There are also some limitation[s] on which UARTs can be used together," picoLemon notes, "as the RP2350 has hard limits on which pins the UART can be assigned [to]. The hardware UART must be different, so for example UART1 and UART3 cannot be used at the same time; in that case you will have to swap the ports. Future versions will use a PIO [Programmable Input/Output] based UART which resolves this restriction and/or having 4 CDC devices."
KiCad project files, Gerbers, and firmware source code for the MultiProbe Pico Debugger have been published on GitHub under the permissive MIT license; fully-assembled boards are available to order on picoLemon's Tindie store at $46.