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Raspberry Pi Debug Probe Test Point Pinout
Intro
The Raspberry Pi Debug Probe is a nice little device for interfacing with UART/SWD devices through USB. Sure, at £10 it’s relatively expensive to the £4 UART probes you can get off Amazon, but those don’t come with SWD, a nice little case, or a much nicer cabling situation. (though I wish they included multiple of each, so you could use UART & SWD at the same time, or just leave the cables connected to a device).
Test Point Pinout
The Debug Probe has a set of test points on the bottom and holes for a 3 pin connector connected to internal points on the board. The problem is they’re not documented very well.
3 pin connector
There’s a unsoldered space for a 3 pin connector. From top to bottom, they’re connected to:
| Shape | TP# |
|---|---|
| Square | 23 |
| Round | 24 |
| Round | 25 |
Test Points
| TP# | Interface | GPIO | Description |
|---|---|---|---|
| 1 | Power | GND | |
| 8 | Power | GND | |
| 11 | Power | GND | |
| 16 | Power | GND | |
| 20 | Power | GND | |
| 24 | Power | GND | |
| 19 | Power | VBUS | 5V (from USB) |
| 26 | Power | IOVDD | 3.3V |
| 27 | Power | DVDD | 1.1V |
| 2 | USB | USB_DM | USB Data - |
| 3 | USB | USB_DP | USB Data + |
| 5 | LED | GPIO2 | Connected to GPIO2 via 470 resistor (for red power LED) |
| 17 | LED | GPIO7 | Connected to GPIO7 via 470 resistor (for green UART_RX LED) |
| 18 | LED | GPIO15 | Connected to GPIO15 via 470 resistor (for green DAP_CONNECTED LED) |
| 21 | LED | GPIO8 | Connected to GPIO8 via 470 resistor (for ywllow UART_TX LED) |
| 22 | LED | GPIO16 | Connected to GPIO16 via 470 resistor (for yellow DAP_TARGET_CONNECTED LED) |
| 6 | System | QSPI_SS | Connected to the BOOTSEL button, in turn, connected to QSPI_SS via 1K resistor (forces the 2040 to boot from USB) |
| 13 | System | RUN | Reset pin |
| 7 | UART1 | GPIO4 | UART1 TX (connected directly to U connector) |
| 9 | UART1 | GPIO5 | UART1 RX (connected directly to U connector). Connected via 74AUP1T17GW to GPIO5, connected directly to GPIO6. |
| 10 | SWD | GPIO10 | SWCLK (connected directly to D connector) |
| 12 | SWD | GPIO13 | SWDIO (connected directly to D connector) Connected via 74AUP1T17GW to GPIO13, connected directly to GPIO14. |
| 14 | SWD (probe) | SWDIO | for the debug probe itsself |
| 15 | SWD (probe) | SWCLK | for the debug probe itsself |
| 23 | GPIO | GPIO0 | |
| 25 | GPIO | GPIO1 |