Using Raspberry Pi 400 keyboard PC as a USB keyboard for your PC

Let’s try not to get confused, but you can now use Raspberry Pi 400 keyboard PC as a standard USB keyboard, optionally with a mouse attached to it, for your computer, or twisted minds may even connect it to a Raspberry Pi SBC… “But why?” you may ask. Because we can.

That’s now possible thanks to work from Phil Howard (Gadgetoid), software lead of Pimoroni, and his Pi400kb project which implements a raw HID keyboard forwarder that turns the Raspberry Pi 400 into a standard USB keyboard.

All you need to do is to find a USB-C to USB-A cable to connect the Raspberry Pi 400 to one of the USB ports on your computer, change some Raspberry Pi OS configuration, and install and run pi400kb.

Add dtoverlay=dwc2 to /boot/config.txt in order to use the dwc2 USB device/gadget mode, and reboot your Pi 400
Load the libcomposite kernel module, get pi400kb binary, and run the program as root:

sudo modprobe libcomposite wget https://github.com/Gadgetoid/pi400kb/blob/main/pi400kb?raw=true chmod +x pi400kb sudo ./pi400kb

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sudo modprobe libcomposite
wget https://github.com/Gadgetoid/pi400kb/blob/main/pi400kb?raw=true
chmod +x pi400kb
sudo ./pi400kb
All good! Try typing on your Raspberry Pi 400 keyboard PC to this if that works

You could also connect a USB mouse to the Pi 400 to save on a USB port on your computer, as both HID events from the keyboard and mouse will be forwarded to the PC. Press Ctrl+C to exit the program

If you prefer to build pi400kb from source, you run the following commands in Pi 400 keyboard computer:

sudo apt install libconfig-dev
git clone https://github.com/Gadgetoid/pi400kb
cd pi400kb
git submodule update --init
mkdir build
cd build
cmake ..
make

sudo apt install libconfig-dev

git clone https://github.com/Gadgetoid/pi400kb

cd pi400kb

git submodule update --init

mkdir build

cd build

cmake ..

make

It does not make a whole lot of sense to use a Raspberry Pi 400 as a USB keyboard, but it could still be useful as a stopgap. For example, if your keyboard stops working, you could always replace it with the Raspberry’s keyboard (PC) until you get a new proper keyboard.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.