Steve Jobs’s NeXT computer company made a keyboard in 1988. With no prior electronics experience, I tried to get it to work over USB. To do so, I had to go way deeper than I ever expected – all the way back over 100 years to broadcast radio standards from the 1920s. I learned tons and tons, and had a lot of fun.
The things people do for the perfect keyboard.
It’s a fun little read. Oscilloscopes are a must for doing this sort of thing. The cheap USB ones that work with sigrok make great sophisticated software signal analyzers that can decode many signals in real time.
Just be aware that ordinary oscilloscopes require a common ground rather than a differential signal (this is a bad design IMHO, but this is how it’s always been done). So be aware it can easily cause shorts and may even damage your USB controller. I’d recommend getting a USB voltage isolator in addition to the USB oscilloscope. They’re both cheap from ebay.
I just use GNU Screen’s built-in support when I need a serial terminal. It’s simpler.
screen /dev/ttyUSB0 19200 8N1in the case of the Soekris net5501 I used to have.