Firstly, ensure that your Raspberry Pi Pico is connected to your computer via a MicroUSB cable.

If you don't have screen installed you can install it on Raspbian (or any Linux distro based on Debian) using sudo apt install screen .

If you're on macOS screen should already be installed.

To open the serial port on Linux use the command screen /dev/ttyACM0 115200 .

The serial port naming conventions are a little different on macOS. To open the serial port on macOS use the command screen /dev/tty.usbmodem0000000000001 115200 .

Note: If it is not showing up as /dev/tty.usbmodem0000000000001 115200 , enter the command ls /dev/tty.usb* to list serial ports derived by a USB device. If you are unsure, unplug the micro USB connector and see which one disappears.

Enter screen /dev/tty.usbmodem0000000000001 115200 and press the return key.

If your terminal window is blank (like this one), press the return key for a prompt.

Your prompt will look like this with >>> . 

We can enter the command help() for instructions on what we can do on the prompt. 

... and this will print out example commands that we can use.

The REPL can execute valid Python code and return the output to us. 

Let's create two variables and add them together.

Type into the REPL a = 2 and then hit the return key.

Now type into the REPL b = 3 and then hit the return key.

We can add the two variables together by typing a + b and then hitting return.

This will output the answer of 5 .

To disconnect from your screen session first press the shortcut control + a.

And then press the shortcut control + \ (backslash).

You'll be asked if you really want to exit, and to do so we'll press the Y key.

We're now back in our regular terminal.