Pico probe test

This repo provides

1. an example code that just blinks LED
2. instruction of
   • build/install openocd device on Ubuntu 2022.04
   • how to use openocd connect you debugger and pico in Clion
3. troubleshooting

Preparation

Hardware

1. You would need to have two MCU module which has the RP2040 MCU on it, on as the debugger and the other one as the target platform.

2. And the debugger should be flashed with a firmware which makes it behaves as an openocd device. A prebuilt firmware can be found in this repo, in the utils folder and is named pico_probe.uf2. Of course, you can build one from its source code. Pin mapping of my prebuilt firmware is different as the official configuration from raspberrypi, my mapping is show as below:

GPIO of RP2040	Function
GPIO2	UART_TX
GPIO3	UART_RX
GPIO4	SWCLK
GPIO5	SWDIO
GPIO6	PROB_RESET

If you don't like my/official configuration you can change it in this file, then build it by yourself.

3. Now you can connect Debugger to the target, connection should be like below:

Debugger	Target	comment
GPIO4	SWCLK
GPIO5	SWDIO
GND	GND
Power(3.3V or 5V)	Power(3.3V or 5V)	optional

Openocd software

The openocd software for RP2040 is a special one, you must build it from its source code. To build it, the official commands suggested by raspberrypi are:

sudo apt install automake autoconf build-essential texinfo libtool libftdi-dev libusb-1.0-0-dev
git clone https://github.com/raspberrypi/openocd.git --branch rp2040 --depth=1 --no-single-branch
cd openocd
./bootstrap
./configure --enable-picoprobe
make -j4
sudo make install # if you have other version of opencd in your system, you should not install it

But, it is possible some errors will show up:

• during ./bootstrap, if you saw any error message, you can execute it again, the second time you execute it, the error message will disappear.
• this one (./configure --enable-picoprobe) could also fail, then you need install pkg-config with

sudo apt install pkg-config

4. To test if you build it correctly:

$ sudo src/openocd -f interface/picoprobe.cfg -f target/rp2040.cfg -s tcl
Open On-Chip Debugger 0.11.0-g610f137 (2022-05-06-14:33)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : only one transport option; autoselect 'swd'
adapter speed: 5000 kHz

Info : Hardware thread awareness created
Info : Hardware thread awareness created
Info : RP2040 Flash Bank Command
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : clock speed 5000 kHz
Info : SWD DPIDR 0x0bc12477
Info : SWD DLPIDR 0x00000001
Info : SWD DPIDR 0x0bc12477
Info : SWD DLPIDR 0x10000001
Info : rp2040.core0: hardware has 4 breakpoints, 2 watchpoints
Info : rp2040.core1: hardware has 4 breakpoints, 2 watchpoints
Info : starting gdb server for rp2040.core0 on 3333
Info : Listening on port 3333 for gdb connections

5. You may wonder if we can execute it without root, yes it is possible. To do so, you need to configure udev rules,
   • execute lsusb in your terminal, the device id is the info we need

   $ sudo lsusb
   Bus 001 Device 021: ID 2e8a:0004 Raspberry Pi Picoprobe
   

   • replace the id you got to the file I provided in utils(2e8a, 0004), name as 99-openocd.rules
   • then copy it to /etc/udev/rules.d, and reload rules

   sudo cp 99-openocd.rules /etc/udev/rules.d/
   sudo udevadm control --reload
   

   • plug out the debugger and replug it in again, now you can execute it without su

Work openocd with Clion

1. Go to File>Setting>Embedded Development, change the openOCD Location to its executable file on your PC, should be under the PATH_OPENOCD_SOURCE_CODE/src/openocd.
   • There is a button called test, you can click it to check if you configured it correctly.
2. Edit the run/debug configuration
3. Now you can flash RP2040 by click a button.

Acknowledgement

1. This work was inspired by this tutorial from ShawnHymel.
2. Of course, most of the instructions and commands can also be found in the documentation of RP2040.
3. The most important part of enabling the CLion to access the customed openocd debugger is to add the udev rule. I followed one answer from StackOverflow.