first progress log

progress-log/2022-03-06-initial-hid-test.md

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+# 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.

test_scripts/test1.py

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+#!/usr/bin/env python3
+import time
+import RPi.GPIO as GPIO
+
+GPIO.setmode(GPIO.BCM)
+GPIO.setup(26, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(16, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+
+NULL_CHAR = chr(0)
+
+def write_report(report):
+    with open('/dev/hidg0', 'rb+') as fd:
+        fd.write(report.encode())
+
+while True:
+    if not(GPIO.input(26)): # 26 = a
+        write_report(NULL_CHAR*2+chr(4)+NULL_CHAR*5)
+        write_report(NULL_CHAR*8)
+    if not(GPIO.input(16)): # 16 = b
+        write_report(chr(32)+NULL_CHAR+chr(5)+NULL_CHAR*5)
+        write_report(NULL_CHAR*8)