Temporary docs/notes (and small change to systemctl service)

docs/noxbox-phase-1.2-GPIO.md

@@ -0,0 +1,61 @@
+# This describes how to use GPIO pins````
+#
+#
+
+Follow wiring guide from sparkfun
+Dont install python
+    install nodejs and npm instead
+then install
+    npm i -g onoff
+Enable i2c
+    https://github.com/fivdi/i2c-bus/blob/master/doc/raspberry-pi-i2c.md
+
+New boot config, when also enabling pull-up for GPIO17 and 27:
+````
+    # See /boot/overlays/README for all available options
+    dtparam=i2c_arm=on
+    dtparam=audio=on
+    gpio=17=pu
+    gpio=27=pu
+
+    dtoverlay=vc4-kms-v3d
+    dtparam=krnbt=on
+    initramfs initramfs-linux.img followkernel
+````
+
+Using it in as NodeJS project to control amp volume using up/down buttons:
+````
+    const i2c = require('i2c-bus');
+    const Gpio = require('onoff').Gpio;
+
+    const MAX9744_ADDR = 0x4B;
+
+    let curVolume = 20;
+
+    async function setVolume(v){
+    const bus = await i2c.openPromisified(1);
+    const wbuf = Buffer.from([v]);
+    bus.i2cWrite(MAX9744_ADDR,wbuf.length,wbuf);
+    bus.close()
+    }
+
+    setVolume(30);
+
+    const upButton = new Gpio(17, 'in', 'both', {activeLow: true});
+    const downButton = new Gpio(27, 'in', 'both', {activeLow: true});
+
+    upButton.watch((err,value) => {
+    if(value && curVolume < 63){
+    console.log('UP');
+    setVolume(++curVolume);
+    }
+    });
+    downButton.watch((err,value) => {
+    if(value && curVolume > 0){
+    console.log('DOWN');
+    setVolume(--curVolume);
+    }
+    });
+
+    console.log("Watching");
+````