1.8 KiB
2022-03-06 Initial HID Test
Found a really old 16gb SD card and loaded Raspbian up on it, then followed a guide to enable wifi and ssh on it before throwing it in the Pi Zero and plugging it in. After a few minutes I was able to ssh in.
I followed a guide to enable it as a HID device, which involves adding this to /boot/config.txt:
dtoverlay=dwc2
And adding this to /etc/modules:
dwc2
libcomposite
Then I created the /raspi_config/hid_usb script that's in this repo at /usr/bin/hid_usb and updated /etc/rc.local to execute it at boot time.
After a reboot, the Pi showed up as a usb device when running lsusb on the computer it's plugged into:
Bus 005 Device 008: ID 1d6b:0104 Linux Foundation Multifunction Composite Gadget
I created the /test_scripts/test1.py script on the Pi and ran it as root, then used a paperclip to alternately connect GPIO 26 and GPIO 16 with ground, and observed it printing characters on the host computer. 26 printed a over and over until I broke the connection, and 16 printed B. Success!
Looking at the pin-out, there are enough GPIO inputs to support well over 6 or 9 buttons directly hand-wired, so I think that's all I need to do. I guess I'd connect one pin on each keyboard switch to ground (maybe all chained together to the same ground pin?) then the other pin from each to a distinct GPIO pin on the Pi.
To further test this theory I got a second paper clip and awkwardly connected both GPIO 26 and 16 to the same ground pin simultaneously and observed aBaBaBaB being output on the host computer. Looking good!
Done messing with the Pi today. Going to mess with OpenSCAD a bit, having just learned about it and worked through a few steps of the introductory tutorial I still have a ways to go before I'll feel comfortable designing the switch plate and case for this thing.