implement simple door controller

.gitignore

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+
+node_modules/
+
+.DS_Store
+._*

README.md

@@ -11,9 +11,30 @@ Project Structure:
 Circuit diagrams are drawn with this [Circuit Simulator](http://www.falstad.com/circuit/).<br/>
 Diagrams are saved as `txt` files, you can import them under `File > Import From Text`.
 
-Embedded System: Raspberry Pi 3.
+Relay Board:
+![](https://github.com/oursky/doorlock/raw/master/embedded/circuit.png)
 
-The release button should be connected between a GPIO pin and ground.<br/>
-The GPIO pin should be configured as an input **with internal pull-up**.
+Embedded System: Raspberry Pi 3
+
+Connections:
+* Release Button: GPIO0/Ground
+* Release Signal: GPIO1/Ground
+
+## Embedded System
+**System:** ArchLinux ARM
+
+**Dependencies:**
+* nodejs
+* npm
+* wiringpi-git (AUR)
+
+**Install as systemd service:**
+```
+[oursky ~/]$ git clone ...
+[oursky ~/]$ sudo cp doorlock/embedded/doorlock.service /etc/systemd/system/
+[oursky ~/]$ sudo systemctl enable doorlock
+[oursky ~/]$ sudo systemctl start doorlock
+```
+**Note: ** If your username is not `oursky`, you need to edit `doorlock.service` accordingly.
 
 ## App

embedded/.npmrc

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+loglevel=silent

embedded/doorlock.service

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+[Unit]
+Description=Doorlock Controller Daemon
+
+[Service]
+User=oursky
+WorkingDirectory=/home/oursky/doorlock/embedded
+ExecStart=/usr/bin/npm start
+
+[Install]
+WantedBy=multi-user.target

embedded/index.js

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+const exec = require('child_process').exec;
+const execSync = require('child_process').execSync;
+const setTimeout = require('timers').setTimeout;
+const log = require('simple-node-logger').createSimpleLogger();
+
+execSync('gpio mode 0 up');
+execSync('gpio mode 1 out');
+
+function openDoor() {
+  execSync('gpio write 1 1');
+  setTimeout(_ => execSync('gpio write 1 0'), 3000);
+}
+
+(function listenButton() {
+  exec('gpio wfi 0 rising').on('exit', _ => {
+    log.info('Unlocked via Button');
+    openDoor();
+    setTimeout(_ => listenButton(), 500);
+  })
+})()
+
+log.info('=== Daemon Started ===');

embedded/package.json

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+{
+  "scripts": {
+    "start": "node index.js"
+  },
+  "dependencies": {
+    "simple-node-logger": "^0.93.12"
+  }
+}