Table of Contents
The default/standard mode, mode 1, exposes various interfaces.
Pinout
Raspberry Pico
| Pin number | Usage | Usage | Pin number |
|---|---|---|---|
| GP0 | stdio UART TX | VBUS | |
| GP1 | stdio UART RX | VSYS | |
| GND | <ground> | <ground> | GND |
| GP2 | SWCLK / TCK | 3V3 EN | |
| GP3 | SWDIO / TMS | 3V3 OUT | |
| GP4 | TDI | ADC VREF | |
| GP5 | TDO / SWO | GP28 / ADC2 | |
| GND | <ground> | <ground> | GND / AGND |
| GP6 | nTRST | GP27 / ADC1 | |
| GP7 | nRESET | GP26 / ADC0 | |
| GP8 | UART TX | RUN | |
| GP9 | UART RX | (1-wire, TODO) | GP22 |
| GND | <ground> | <ground> | GND |
| GP10 | UART CTS | SCL | GP21 |
| GP11 | UART RTS | SDA | GP20 |
| GP12 | MISO | GP19 | |
| GP13 | nCS | GP18 | |
| GND | <ground> | <ground> | GND |
| GP14 | SCLK | GP17 | |
| GP15 | MOSI | GP16 | |
| <end> | <bottom> | <bottom> | <end> |
Functions
UART
The UART interface allows one to interact with another device over a UART port, using a USB-CDC device (/dev/ttyACMx). Baudrate and other line coding settings are applied from the settings from the USB-CDC host, and thus require no special configuration tool.
It is possible to enable hardware flow control (using CTS and RTS lines), it can be enabled or disabled using dpctl uart-cts-rts.
JTAG and SWD
The device exposes CMSIS-DAP functionality over a USB HID interface, which can be used for JTAG or SWD debugging. No special configuration is required to use it.
In SWD mode, the pin mapping is entirely as with the standard Picoprobe setup, as described in Chapter 5 and Appendix A of Getting Started with Raspberry Pi Pico. It has additional experimental SWO support on the TDO/SWO pin, but has not been properly tested yet.
In JTAG mode, TCK and TMS have the same pins as SWCLK and SWDIO, respectively, TDI and TDO are on the next two consecutive free pins.
Note that, after having used JTAG mode, the device has to be power-cycled in order to use SWD mode again. This is a known bug.
In your OpenOCD flags, use -f interface/cmsis-dap.cfg. Default transport is
JTAG, if OpenOCD doesn't specify a default to the probe. (OpenOCD usually defaults to SWD in most cases.)
SPI
The SPI interface can be used in two ways: using a serprog USB-CDC interface, mostly useful for interacting with SPI flash chips, and a kernel module, for generic SPI operations, though the Linux spidev interface.
For Serprog, use the following flashrom options (if /dev/ttyACM1 is the USB
serial device on your machine corresponding to the Serprog CDC interface of the
Pico):
flashrom -c <flashchip> -p serprog:dev=/dev/ttyACM1:115200 <rest of the read/write cmd>
Different serial speeds can be used, too. Serprog support is techincally untested, as in it does output the correct SPI commands as seen by my logic analyzer, but I don't have a SPI flash chip to test it on.
I2C
I2C is exposed only through a Linux kernel module, which can then be used by standard Linux I2C tools (such as utilities from the i2c-tools package, eg. i2cget, i2cset, i2cdetect). The i2c-dev module needs to be loaded for this to work.
Using i2cdetect -l, you should be able to see which I2C device belongs to
the tool:
$ sudo i2cdetect -l
[...]
i2c-1 i2c i915 gmbus dpb I2C adapter
i2c-8 i2c Radeon i2c bit bus 0x95 I2C adapter
i2c-15 i2c dragonprobe-i2c-1-1:1.0 I2C adapter
i2c-6 i2c Radeon i2c bit bus 0x93 I2C adapter
i2c-13 i2c AUX C/DDI C/PHY C I2C adapter
Temperature sensor
If the board/MCU has a temperature sensor, it is made available as a Linux hwmon kernel module, making the output available for use in lm_sensors output.
Additionally, it can also be configured to appear on the device's I2C bus as an emulated I2C device, pretending to be a JC42-compliant temperature sensor (more precisely, the Microchip MCP9808). This can be achieved using dpctl tempsensor (with BUSNUM the number from the above
i2cdetect -l output):
$ ./dpctl.sh tempsensor --set 0x18 # need to give it an address first
$ sudo modprobe jc42
$ # now tell the jc42 module that the device can be found at this address
$ echo "jc42 0x18" | sudo tee /sys/bus/i2c/devices/i2c-BUSNUM/new_device
$ sudo sensors # it should show up now:
jc42-i2c-BUSNUM-18
Adapter: dragonprobe-i2c at bus 001 device 032
temp1: +23.1°C (low = -20.0°C)
(high = +75.0°C, hyst = +75.0°C)
(crit = +80.0°C, hyst = +80.0°C)
Temperature readout may be a bit higher than the ambient temperature.
1-wire
This part is still TODO