Accessing the BBC micro:bit REPL on Gentoo

The micro:bit repl in a terminal

Thanks to the National Computer Science School, [1] I'm now the proud owner of a BBC micro:bit. The micro:bit has the ability to provide a python REPL over USB serial but when plugging it into my Gentoo machine, the micro:bit doesn't show up in /dev. What gives?

Like most things, a kernel module is required to provide the drivers for the USB serial interface. On first inspection you would think that CONFIG_USB_SERIAL_CONSOLE is the correct module, but no. The micro:bit's REPL is actually treated as a USB modem which requires CONFIG_USB_ACM to be set.

Kernel Configuration

	Device Drivers --->
	    [*]  USB Support --->
	        <*>  USB Modem (CDC ACM) support

Now that the module is enabled, rebuild the kernel [2] and reboot. Once rebooted plug in the micro:bit and there should be a new device in /dev called /dev/ttyACM0 (or something similar). Now it's as simple as connecting to your micro:bit REPL using your serial console client of choice!

	picocom /dev/ttyACM0 -b 115200

The micro:bit documentation as some more examples. [3]