Added i2c-amp-control service

i2c-amp-control/i2c-amp-control.service

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+[Unit]
+Description=I2C Amplifier controller
+
+[Service]
+ExecStart=node /data/services/i2c-amp-control/index.js
+WorkingDirectory=/data/services/i2c-amp-control
+Restart=always
+# Restart service after 10 seconds if node service crashes
+RestartSec=10
+# Output to syslog
+StandardOutput=syslog
+StandardError=syslog
+SyslogIdentifier=i2c-amp-control
+#Environment=NODE_ENV=production PORT=1337
+
+[Install]
+WantedBy=multi-user.target

i2c-amp-control/index.js

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+const Gpio = require('onoff').Gpio;
+const i2c = require('i2c-bus');
+
+const MAX9744_I2CADDR = 0x4b;
+const MAX_VOLUME = 63;
+const MIN_VOLUME = 0;
+const VOLUME_STEPS = 1;
+
+let currentVolume = MIN_VOLUME;
+let i2c1;
+
+async function readVolume() {
+    const rBuf = Buffer.alloc(1);
+    const data = await i2c1.i2cRead(MAX9744_I2CADDR, rBuf.length, rBuf);
+    return data.buffer.readUInt8();
+}
+
+async function writeVolume(volume) {
+    const wBuf = Buffer.from([volume]);
+    await i2c1.i2cWrite(MAX9744_I2CADDR, wBuf.length, wBuf);
+    console.log("Volume set: ", volume);
+}
+
+async function increaseVolume() {
+    console.log("Increasing volume");
+    currentVolume = currentVolume < MAX_VOLUME - VOLUME_STEPS ? currentVolume + VOLUME_STEPS : MAX_VOLUME;
+    await writeVolume(currentVolume);
+}
+
+async function decreaseVolume() {
+    console.log("Decreasing volume");
+    currentVolume = currentVolume > MIN_VOLUME + VOLUME_STEPS ? currentVolume - VOLUME_STEPS : MIN_VOLUME;
+    await writeVolume(currentVolume);
+
+}
+
+async function handleButtonTick(button) {
+    console.log("Handling button tick");
+    if(button.active) {
+        await button.action();
+        button.cycles++;
+        let timeout = 1400 - (button.cycles * 200);
+        if(timeout < 200) {
+            timeout = 200;
+        }
+        button.watcher = setTimeout(async () => {
+            await handleButtonTick(button);
+        }, timeout);
+    } else if(button.watcher) {
+        clearTimeout(button.watcher);
+        button.cycles = 0;
+    }
+}
+
+const buttons = {
+    volumeUp: {pin: 17, gpio: null, active: false, watcher: null, action: increaseVolume, cycles: 0},
+    volumeDown: {pin: 27, gpio: null, active: false, watcher: null, action: decreaseVolume, cycles: 0}
+};
+function watchButton(button) {
+    button.gpio.watch(async (err, value) => {
+        if(err) {
+            button.active = false;
+            if(button.watcher) {
+                clearInterval(button.watcher);
+                button.cycles = 0;
+            }
+            console.error(err);
+        } else {
+            if (value === 1) {
+                button.active = true;
+                await handleButtonTick(button);
+            } else {
+                button.active = false;
+                if(button.watcher) {
+                    clearInterval(button.watcher);
+                }
+            }
+        }
+    });
+}
+
+function initButton(button) {
+    button.gpio = new Gpio(button.pin, 'in', 'both', { activeLow: true});
+    watchButton(button);
+}
+
+async function main() {
+    try {
+        i2c1 = await i2c.openPromisified(1);
+        currentVolume = await readVolume();
+
+        initButton(buttons.volumeUp);
+        initButton(buttons.volumeDown);
+    } catch (err) {
+        console.error(err);
+    }
+}
+main();

i2c-amp-control/install.sh

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+npm i
+
+SERVICE="i2c-amp-control"
+SERVICE_FOLDER="/data/services/$SERVICE"
+mkdir -p "$SERVICE_FOLDER"
+cp ./index.js "$SERVICE_FOLDER"
+cp -r ./node_modules "$SERVICE_FOLDER"
+
+cp $SERVICE.service /etc/systemd/system
+if systemctl list-units | grep "$SERVICE"; then
+  systemctl restart "$SERVICE.service"
+  echo "$SERVICE service restarted"
+else
+  systemctl enable "$SERVICE.service"
+  systemctl start "$SERVICE.service"
+  echo "Enabled and started $SERVICE"
+fi

i2c-amp-control/package.json

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+{
+  "scripts": {},
+  "dependencies": {
+    "i2c-bus": "^5.2.2",
+    "onoff": "^6.0.3"
+  }
+}