First pass at the API 🦄

.eslintignore

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+dist
+node_modules

.eslintrc.yml

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+---
+parser: babel-eslint
+parserOptions:
+  ecmaVersion: 6
+  sourceType: module
+  ecmaFeatures:
+    impliedStrict: true
+    experimentalObjectRestSpread: true
+globals:
+  Promise: true
+env:
+  browser: true
+  jest: true
+  node: true
+  commonjs: true
+extends:
+  - eslint:recommended
+rules:
+  no-empty: warn
+  no-console: off
+  semi:
+    - error
+    - never

.gitignore

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+#-----------------------------------
+# Application specific files
+#-----------------------------------
+
+node_modules
+dist
+
+
+#-----------------------------------
+# Build artifacts
+#-----------------------------------
+
+.cache
+.awcache
+*.bk
+
+
+#-----------------------------------
+# Editor files
+#-----------------------------------
+
+.vscode
+
+
+#-----------------------------------
+# Logs/database files
+#-----------------------------------
+
+*.log
+*.sql
+*.sqlite
+
+
+#-----------------------------------
+# OS generated files
+#-----------------------------------
+
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db

.prettierignore

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+.vscode
+dist
+node_modules
+package-lock.json

.prettierrc

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+{
+  "semi": false,
+  "singleQuote": true,
+  "trailingComma": "es5"
+}

README.md

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+# usbrelay
+
+**THIS IS CURRENTLY IN AN EXPERIMENTAL STATE:** It does not yet support multiple boards or other manufacturers. Coming soon...
+
+> A Node.js library to control USB connected relays
+
+## Setup
+
+```bash
+npm install --save usbrelay
+```
+
+## Usage
+
+```js
+const { Board } = require('usbrelay')
+
+const numRelays = 2
+const relays = new Board(numRelays)
+
+// Turn all relays off:
+relays.allOff()
+
+// Turn all relays on:
+relays.allOn()
+
+// Turn relay #1 on:
+relays.on(1)
+
+// Turn relay #1 off:
+relays.off(1)
+```
+
+Please see [examples directory](/examples) for more examples on using `usbrelay`
+
+## API
+
+### `relays.allOff()`
+
+Turn all relays off.
+
+### `relays.allOn()`
+
+Turn all relays on.
+
+### `relays.on(index)`
+
+Turn relay with `index` on. Index starts at `1` and goes to the number of available relays. Throws an exception if the relay `index` is greater than the available number of relays.
+
+### `relays.off(index)`
+
+Turn relay with `index` off. Index starts at `1` and goes to the number of available relays. Throws an exception if the relay `index` is greater than the available number of relays.
+
+## Contribute
+
+Contributions welcome! Please submit a Pull Request and make sure to format your code with Prettier and write tests!
+
+## License
+
+MIT
+
+## Credits
+
+© [Dana Woodman](http://danawoodman.com) 2018

examples/simple.js

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+const { Board } = require('../src/relays')
+
+const numRelays = 2
+const relays = new Board(numRelays)
+
+// Make sure the relay defaults to off
+relays.allOff()
+
+relays.on(1)
+setTimeout(() => relays.off(1), 500)
+setTimeout(() => relays.on(2), 500)
+setTimeout(() => relays.allOn(), 1000)
+setTimeout(() => relays.allOff(), 2000)

package.json

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+{
+  "name": "usbrelay",
+  "version": "0.0.1",
+  "description": "A USB relay support library",
+  "main": "src/relay.js",
+  "scripts": {
+    "test": "jest"
+  },
+  "repository": {
+    "type": "git",
+    "url": "github.com/danawoodman/usbrelay"
+  },
+  "keywords": [
+    "usb",
+    "relay",
+    "arduino",
+    "rpi",
+    "raspberry",
+    "pi",
+    "linux",
+    "switch",
+    "control",
+    "iot",
+    "electronics",
+    "diy"
+  ],
+  "author": "Dana Woodman <dana@danawoodman.com> (http://danawoodman.com/)",
+  "license": "MIT",
+  "dependencies": {
+    "node-hid": "0.7.3"
+  },
+  "devDependencies": {
+    "babel-eslint": "8.2.6",
+    "eslint": "5.1.0",
+    "jest": "23.4.1",
+    "nodemon": "1.18.3",
+    "prettier": "1.13.7"
+  }
+}

src/board.js

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+/**
+ * Control a USB relay board using USB.
+ *
+ * This code helped a lot in the understanding of what they boards
+ * expect for hex inputs:
+ * https://github.com/jaketeater/Very-Simple-USB-Relay/blob/master/relay.py
+ */
+const HID = require('node-hid')
+
+const ALL_ON = 0xfe
+const ALL_OFF = 0xfc
+const ON = 0xff
+const OFF = 0xfd
+const VENDOR_ID = 5824
+const PRODUCT_ID = 1503
+
+// convert integer to binary representation
+const itob = num => Number(parseInt(num, 10).toString(2))
+
+class Board {
+  constructor(numRelays = 1, debug = true) {
+    if (debug) console.log('NUMBER OF RELAYS:', numRelays)
+
+    this.debug = debug
+
+    this.numRelays = numRelays
+    this.relays = Array.from(Array(this.numRelays).keys())
+
+    this.board = new HID.HID(VENDOR_ID, PRODUCT_ID)
+    if (!this.board) throw new Error('No device found!')
+
+    this.board.on('data', data => console.log('DATA:', data))
+    this.board.on('error', error => console.error('ERROR:', error))
+
+    this.logState()
+  }
+
+  getState() {
+    const binaryState = itob(this.board.getFeatureReport(1, 8)[7])
+    const state = String(binaryState)
+      .split('')
+      .map(Number)
+      .map(v => (v === 0 ? OFF : ON))
+    return this.relays.map(index => state[index] || state[0])
+  }
+
+  logState() {
+    if (!this.debug) return
+
+    console.log('STATE:')
+    this.getState().map((state, index) =>
+      console.log('-> RELAY:', index, 'STATE:', state === OFF ? 'OFF' : 'ON')
+    )
+  }
+
+  checkIndex(index) {
+    if (index && !this.relays[index])
+      throw new Error('Provided index is invalid')
+  }
+
+  on(index) {
+    this.checkIndex()
+    this.trigger([ON, index])
+  }
+
+  off(index) {
+    this.checkIndex()
+    this.trigger([OFF, index])
+  }
+
+  allOn() {
+    this.trigger([ALL_ON])
+  }
+
+  allOff() {
+    this.trigger([ALL_OFF])
+  }
+
+  trigger(state) {
+    this.logState()
+    this.board.sendFeatureReport(state)
+  }
+}
+
+module.exports = Board

src/relays.js

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+// TODO: enumerate on all USB relay boards
+const Board = require('./board')
+module.exports = { Board }