When building a converter, I just test the USB interface on the same PC that uploads the firmware. But sometimes the converter works with several keyboards and I need to test any firmware upgrade on all of them that aren't in storage. Or an MCU moves from a breadboard to a permaproto. The soldering workstation is in another room from the desk for ventilation.
So, a couple of years ago I built this from a Raspberry Pi Zero, OLED hat, and USB hub pogo-plugged-thingy.
- pi-kbd-tester-side.jpg (285.55 KiB) Viewed 1596 times
- pi-kbd-tester-bottom.jpg (402.8 KiB) Viewed 1596 times
It displays each USB event with the current state of down keys, plus total count of pressed and unique keys, giving a quick check that everything is working. (To be more precise, that it is
still working, since it isn't really suitable for actual debugging.)
- pi-kbd-tester-A.jpg (201.42 KiB) Viewed 1596 times
- pi-kbd-tester-PSCN.jpg (210.94 KiB) Viewed 1596 times
- pi-kbd-tester-KP.jpg (193.59 KiB) Viewed 1596 times
The joystick selects modes. The key buttons turn on the three main keyboard LEDs. It also has a simple text box for a quick typing test.
- pk-kbd-tester-text.jpg (213.64 KiB) Viewed 1596 times
I recently updated it to recognize CDC devices too for all the ASCII keyboards I've ended up with, which just convert to a serial port.
- pi-kbd-tester-ascii.jpg (313.3 KiB) Viewed 1596 times
The file system is mounted read-only, so even though there's an actual shutdown command, nothing particularly bad happens should it crash or get unplugged.
