Installing MicroPython
To install or upgrade MicroPython on a Pico there are three steps.
1. Download the UF2 file. There is a vanilla version available from micropython.org, or if you are using one of Pimoroni's boards then you can select one of the UF2 files with all their libraries preinstalled here.
2. Put the Pico into BootLoader mode by unplugging it, hold the BOOTSEL button down and then plugging it back in. The Pico will then appear as a USB device on the host machine.
3. Copy the UF2 file into the new USB device
Once the file has been copied over, the USB device will disappear.
Testing the MicroPython
As the Pico has no built-in display, it can only communicate via the USB. The MicroPython firmware has a built-in serial port available over the USB.
To access it, the popular Minicom package is used.
Install it on your Pi using:
sudo apt install minicom
Next, identify the serial port.
The Pico should appear as a port of the form /dev/ttyACM.
Use
ls /dev/tty*
If it is unclear which port is the Pico, unplug it and try again, identifying which device disappears.
Connect to the MicroPython running on the Pico using:
minicom -o -D /dev/ttyACM0
This should display the Minicom opening text:
OPTIONS: I18n
Compiled on Aug 13 2017, 15:25:34.
Port /dev/ttyACM0, 07:39:31
Press CTRL-A Z for help on special keys
You now need to soft reboot, press Control and D. This will display information about the installed MicroPython and the prompt >>>.
MPY: soft reboot
MicroPython v1.15 on 2021-04-18; Raspberry Pi Pico with RP2040
Type "help()" for more information.
>>>
To test the MicoPython, try the classic:
>>> print("hello")
hello
>>>
This shows that MicroPython is running successfully on your Pico.
Control A then Z brings up help.
Control X closes Minicom.
References
https://micropython.org/download/rp2-pico/rp2-pico-latest.uf2
https://github.com/pimoroni/pimoroni-pico/releases
https://datasheets.raspberrypi.org/pico/raspberry-pi-pico-python-sdk.pdf
https://en.wikipedia.org/wiki/Minicom
