Raspberry Pi Debug Probe: specs and pinout
USB debug kit from Raspberry Pi with a CMSIS-DAP SWD interface and a UART bridge, built on Raspberry Pi Pico hardware, for programming and debugging Pico and RP2040 boards from Windows, macOS or Linux.
Specs
| Spec | Value | Source |
|---|---|---|
| Interfaces | USB to Arm Serial Wire Debug (SWD) bridge and USB to UART bridge; CMSIS-DAP compatible; works with OpenOCD and other CMSIS-DAP tools | source Product brief p.3, Specification: Features |
| Nominal I/O voltage | 3.3 V | source Product brief p.3, Specification |
| Operating temperature | -20 to +70 C | source Product brief p.3, Specification |
| Debug connector | Raspberry Pi 3-pin debug connector (3-pin JST-SH): 'D' port for SWD, 'U' port for UART | source Product brief p.2-3; documentation: Getting started |
| Included cables | USB cable and three debug cables: 3-pin JST to 3-pin JST, 3-pin JST to 0.1-inch header (female), 3-pin JST to 0.1-inch header (male) | source Product brief p.3, Specification: Included |
| Firmware | Based on Raspberry Pi Pico hardware; runs the open-source Picoprobe software, updated like Pico firmware | source Product brief p.2, Overview |
| Host serial port | UART traffic appears on the host as a CDC serial port (for example /dev/ttyACM0 on Raspberry Pi OS) | source Documentation: Serial connections |
| Indicators | One red power LED and four activity LEDs | source Documentation: The Debug Probe |
| Form factor | 22 mm x 32 mm | source Product brief p.3, Specification |
Power
| Value | Source | |
|---|---|---|
| Supply | Over its USB cable from the host computer (the probe has a red power LED) | source Documentation: The Debug Probe; no current figure is published in the product brief |
Pinout
Rows are the two 3-pin debug ports described in the Raspberry Pi documentation. The pin order inside the JST-SH connector is set by the Raspberry Pi 3-pin Debug Connector Specification, which this page does not cover, so rows are identified by the wire colour of the 0.1-inch header cables.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| U port, orange wire | TX (output from the probe) | 3.3 V | Connects to the target's RX pin | source Documentation: The Debug Probe and Getting started |
| U port, black wire | GND | 0 V | source Documentation: The Debug Probe | |
| U port, yellow wire | RX (input to the probe) | 3.3 V | Connects to the target's TX pin | source Documentation: The Debug Probe and Getting started |
| D port, orange wire | SC (SWCLK, output from the probe) | 3.3 V | Connects to the target's SWCLK | source Documentation: The Debug Probe and Getting started |
| D port, black wire | GND | 0 V | source Documentation: The Debug Probe | |
| D port, yellow wire | SD (SWDIO, input to the probe or I/O) | 3.3 V | Connects to the target's SWDIO | source Documentation: The Debug Probe and Getting started |
Build with it
Project ideas for the Raspberry Pi Debug Probe. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Pico firmware upload and breakpoints: Connect the probe's D port to the Pico's SWCLK, GND and SWDIO pads or header, then upload and debug over SWD without pressing BOOTSEL. Power the Pico from its own micro-USB cable and connect GND first. If your Pico has no 3-pin debug socket, solder a 3-pin header to its SWD pads first.
- Pico serial log monitor: The probe's U port connects to the Pico's UART0 pins (TX on GP0, RX on GP1) and shows up on the computer as a serial port. The DHT22 runs from 3.3 V to 6 V, so it can use the Pico's 3.3 V output. Learning project.
- Pi Zero serial console: The Zero W's UART pins are 3.3 V, matching the probe's 3.3 V I/O. Cross TX and RX, connect GND first, and power the Zero W from its own supply. The serial console must be enabled in the operating system.
Common mistakes
- Attaching signal wires before ground when the target has its own supply: connect GND first, or remove power from the target, because a voltage difference can damage the probe (source: link, Warning in 'The Debug Probe')
- Wiring TX to TX: the probe's RX goes to the target's TX pin and the probe's TX goes to the target's RX pin (source: link, Getting started)
- Connecting the probe to a 5 V target: the probe's nominal I/O voltage is 3.3 V and connecting incompatible devices may damage the unit (source: link, p.3-4)
Not covered by the official source
- The product brief gives no supply current for the probe.
- The 3-pin debug connector specification (rptl.io/debug-spec) is not covered here, so the pin order inside the JST-SH connector is not listed.