# Source: introduction.adoc

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== About the Debug Probe

image::images/debug-probe.jpg[width="100%"]

The Raspberry Pi Debug Probe is a USB device that provides both a UART serial port and a standard Arm Serial Wire Debug (SWD) interface. The probe is designed for easy, solderless, plug-and-play debugging. It has the following features:

* USB to Arm https://developer.arm.com/documentation/ihi0031/a/The-Serial-Wire-Debug-Port\--SW-DP-/Introduction-to-the-ARM-Serial-Wire-Debug\--SWD\--protocol[Serial Wire Debug] (SWD) port
* USB to UART bridge
* Compatible with the https://developer.arm.com/documentation/101451/0100/About-CMSIS-DAP[CMSIS-DAP] standard
* Works with https://openocd.org/[OpenOCD] and other tools supporting CMSIS-DAP
* Open source, easily upgradeable firmware

NOTE: For more information on the Raspberry Pi three-pin debug connector see the https://rpltd.co/debug-spec[specification].

This makes it easy to use a Raspberry Pi Pico on platforms such as Windows, macOS, and Linux that lack a GPIO header to connect directly to the Pico's serial UART or SWD port.

=== The Debug Probe

The probe operates at 3.3V nominal I/O voltage.

image:images/the-probe.png[width="70%"]

Included with the Debug Probe is a USB power cable and three debug cables:

* three-pin JST-SH connector to 3-pin JST-SH connector cable
* three-pin JST-SH connector to 0.1-inch header (female)
* three-pin JST-SH connector to 0.1-inch header (male)

The two 0.1-inch header cables — intended for breadboard (male) or direct connection to a board with header pins (female) — are coloured as below:

Orange:: TX/SC (Output from Probe)
Black:: GND
Yellow:: RX/SD (Input to Probe or I/O)

The cable with three-pin JST-SH connectors is intended to be used with the https://rpltd.co/debug-spec[standard three-pin connector] that newer Raspberry Pi boards use for the SWD debug port and UART connectors.

WARNING: When the target is powered from a separate power source or computer, ensure a common reference before connecting signal lines. Either remove power from the target or connect GND between the target and the Raspberry Pi Debug Probe first; you can attach RX, TX, SC, and SD after GND is connected. Potential voltage differences between the two systems can cause damage to the probe.

The Debug Probe has five LEDs, a red LED to indicate power, and four more activity indicator LEDs

image::images/debug-leds.png[width="70%"]

NOTE: OpenOCD switches both DAP LEDs on when the target is connected, and turns them off when it calls `DAP_DISCONNECT`.