Adding an internal USB hub

A project log for Thumb Term

Battery powered Linux-terminal handheld with front and rear inputs, 4.3" DSI LCD, a Pi 3A+, and GPIO breakout. WIP.

dan-a8ksh4Dan (a8ksh4) 09/30/2023 at 17:350 Comments

Because I really just want this project to work so I can move forward, I gave up on the keyboard stuff over UART and hooked the Pi Pico up to USB.  I still want to have the external USB port on the Pi 3a to work, so here's the process I used:

It works!!!  'lsusb' reports the hub and the Pico, and now I have /dev/ttyACM0 listed for serial communication with the Pico.

The essential thing I've found for running USB2.0 around like this is to keep the D+ and D- wires right next to each other for impedance matching - they act as a tuned transmission line and for anything but short distances, they need to be run together.  The blue and white wires in the photos here are D+ and D-.