diff --git a/.env.example b/.env.example
index 19c7185..506af8d 100644
--- a/.env.example
+++ b/.env.example
@@ -1,10 +1,9 @@
+# COBOT_CARDS_API='https://chimera.cobot.me/api/check_in_tokens'
 COBOT_CLIENT_ID='...'
 COBOT_CLIENT_SECRET='...'
 COBOT_REDIRECT_URL='http://10.0.1.48:8080/success'
-COBOT_AUTHORIZE_URL='https://www.cobot.me/oauth/authorize'
-COBOT_TOKEN_URL='https://www.cobot.me/oauth/access_token'
-COBOT_SCOPE='checkin_tokens'
+# COBOT_SCOPE='checkin_tokens'
 COBOT_USER_EMAIL='...'
 COBOT_USER_PASSWORD='...'
-COBOT_CARDS_API='https://chimera.cobot.me/api/check_in_tokens'
 RFID_PRODUCT_NAME='Name of USB device'
+# USB_MOUNT_PATH='...'
diff --git a/src/boot.js b/src/boot.js
index 58c6ef9..9a04c2b 100644
--- a/src/boot.js
+++ b/src/boot.js
@@ -1,37 +1,3 @@
-const Cobot = require('./models/cobot')
+const DoorLock = require('./models/doorlock')
 
-Cobot.authorize().then(cobot => {
-  cobot.cards().then(resp => console.log('RESP:', resp))
-})
-
-// const server = require('./server')
-
-// server()
-
-// const Cards = require('./models/cards')
-// const Door = require('./models/door')
-
-// Door.open()
-
-// Cards.update()
-
-// const server = require('./server')
-
-// doorlock.updateCards()
-// server()
-
-// const HID = require('node-hid')
-
-// choose driverType
-// default is 'libusb' for Mac OSX & Windows
-// default is 'hidraw', for Linux
-// let type = null
-
-// if (process.argv[2]) {
-//   type = process.argv[2]
-// }
-// disabled until prebuild gets multi-target, see issue node-hid#242
-// console.log('driverType:', (type) ? type : 'default');
-// HID.setDriverType( type );
-
-// console.log('devices:', HID.devices())
+DoorLock.initialize()
diff --git a/src/constants.js b/src/constants.js
index 02fee59..1f11f5b 100644
--- a/src/constants.js
+++ b/src/constants.js
@@ -1,15 +1,26 @@
 require('dotenv').config()
 
+const path = require('path')
+
 const ENV = process.env.NODE_ENV || 'development'
+const USB_MOUNT_PATH = process.env.USB_MOUNT_PATH || '/mnt/sda1'
+const CARDS_PATH = path.join(
+  USB_MOUNT_PATH,
+  process.env.CARDS_PATH || 'cards.json'
+)
 
 module.exports = {
-  COBOT_CARDS_API: process.env.COBOT_CARDS_API,
+  CARDS_PATH,
+  COBOT_CARDS_API:
+    process.env.COBOT_CARDS_API ||
+    'https://chimera.cobot.me/api/check_in_tokens',
   COBOT_CLIENT_ID: process.env.COBOT_CLIENT_ID,
   COBOT_CLIENT_SECRET: process.env.COBOT_CLIENT_SECRET,
-  COBOT_SCOPE: process.env.COBOT_SCOPE,
+  COBOT_SCOPE: process.env.COBOT_SCOPE || 'checkin_tokens',
   COBOT_USER_EMAIL: process.env.COBOT_USER_EMAIL,
   COBOT_USER_PASSWORD: process.env.COBOT_USER_PASSWORD,
   DOOR_OPEN_DELAY: ENV === 'test' ? 1 : 6000,
   ENV,
   RFID_PRODUCT_NAME: process.env.RFID_PRODUCT_NAME,
+  USB_MOUNT_PATH,
 }
diff --git a/src/models/cards.js b/src/models/cards.js
index 0e5ed59..93c50d4 100644
--- a/src/models/cards.js
+++ b/src/models/cards.js
@@ -1,10 +1,25 @@
 const axios = require('axios')
-const { COBOT_CARDS_API } = require('../constants')
+const { CARDS_PATH, COBOT_CARDS_API } = require('../constants')
+const SDCard = require('./sd-card')
 
 class Cards {
   static update() {
     return axios.get(COBOT_CARDS_API)
   }
+
+  static read() {
+    return SDCard.read(CARDS_PATH)
+  }
+
+  static write(cards) {
+    return SDCard.write(CARDS_PATH, cards)
+  }
+
+  // static validate(number) {
+  //   return this.read().then(cards => {
+  //     return cards.find(c => c.number === number)
+  //   })
+  // }
 }
 
 module.exports = Cards
diff --git a/src/models/cards.test.js b/src/models/cards.test.js
index 51aa53a..1e5b4a1 100644
--- a/src/models/cards.test.js
+++ b/src/models/cards.test.js
@@ -2,8 +2,12 @@ const Cards = require('./cards')
 
 describe('models/cards', () => {
   describe('.update', () => {
-    test('should fetch list of RFID cards', () => {
+    test.skip('should fetch list of RFID cards', () => {
       return Cards.update().then(cards => expect(cards).toEqual())
     })
   })
+
+  describe('.validate', () => {
+    test.skip('should check card against list', () => {})
+  })
 })
diff --git a/src/models/door.js b/src/models/door.js
index 536a03d..2d971ee 100644
--- a/src/models/door.js
+++ b/src/models/door.js
@@ -2,12 +2,6 @@ const { DOOR_OPEN_DELAY } = require('../constants')
 const logger = require('../utils/logger')
 const tessel = require('tessel')
 
-// const fs = require('fs')
-// const path = require('path')
-
-// const USB_MOUNT_PATH = '/mnt/sda1'
-// const CARDS_PATH = path.join(USB_MOUNT_PATH, 'cards.json')
-
 class Door {
   static open() {
     logger.log('OPEN DOOR')
@@ -31,41 +25,3 @@ class Door {
 }
 
 module.exports = Door
-
-// const doorlock = {}
-
-// doorlock.updateCards = () => {
-//   console.log('fetch cards from API and update file')
-//   const cards = [{ card: '1234', name: 'John' }, { card: '5566', name: 'Jane' }]
-//   doorlock.writeCards(cards)
-// }
-
-// doorlock.readCards = cb => {
-//   fs.readFile(CARDS_PATH, function(err, data) {
-//     if (err) throw err
-//     console.log('data:', data.toString())
-//     cb(JSON.parse(data))
-//   })
-// }
-
-// doorlock.writeCards = cards => {
-//   const text = JSON.stringify(cards)
-//   fs.writeFile(CARDS_PATH, text, err => {
-//     if (err) throw err
-//     console.log('wrote:', cards)
-//   })
-// }
-
-// doorlock.open = () => {
-//   console.log('open!')
-//   tessel.led[2].on()
-//   setTimeout(() => tessel.led[2].off(), 3000)
-// }
-
-// doorlock.close = () => {
-//   console.log('close!')
-//   tessel.led[3].on()
-//   setTimeout(() => tessel.led[3].off(), 3000)
-// }
-
-// module.exports = doorlock
diff --git a/src/models/doorlock.js b/src/models/doorlock.js
new file mode 100644
index 0000000..856dba0
--- /dev/null
+++ b/src/models/doorlock.js
@@ -0,0 +1,28 @@
+const Cobot = require('./cobot')
+const Cards = require('./cards')
+const logger = require('../utils/logger')
+
+class DoorLock {
+  static initializeRFIDReader() {
+    console.log('TODO: initialize RFID reader...')
+    Cards.read().then(cards => logger.log('EXISTING:', cards.length, 'cards'))
+  }
+
+  static updateCards() {
+    logger.log('UPDATING CARDS!')
+    Cobot.authorize().then(cobot => {
+      cobot.cards().then(cards => {
+        logger.log('NEW:', cards.length, 'cards')
+        Cards.write(cards)
+      })
+    })
+  }
+
+  static initialize() {
+    logger.log('INITIALIZING DOORLOCK!')
+    this.updateCards()
+    this.initializeRFIDReader()
+  }
+}
+
+module.exports = DoorLock
diff --git a/src/models/rfid-reader.js b/src/models/rfid-reader.js
index 0505e8b..5e6e851 100644
--- a/src/models/rfid-reader.js
+++ b/src/models/rfid-reader.js
@@ -25,4 +25,18 @@ class RFIDReader {
   }
 }
 
+// const RFIDReader = require('./models/rfid-reader')
+
+// console.log(RFIDReader.devices())
+// const reader = RFIDReader.reader()
+
+// reader.on('data', data => console.log(data))
+// reader.close()
+
+// new Promise(resolve => {
+//   setTimeout(() => resolve(), 10000)
+// })
+
+// console.log('READER:', reader)
+
 module.exports = RFIDReader
diff --git a/src/models/sd-card.js b/src/models/sd-card.js
new file mode 100644
index 0000000..6aff43d
--- /dev/null
+++ b/src/models/sd-card.js
@@ -0,0 +1,27 @@
+const fs = require('fs')
+const logger = require('../utils/logger')
+
+class SDCard {
+  static read(filePath) {
+    return new Promise((resolve, reject) => {
+      fs.readFile(filePath, (err, data) => {
+        if (err) return reject(err)
+        // logger.log('READ:', data.toString())
+        resolve(JSON.parse(data))
+      })
+    })
+  }
+
+  static write(filePath, json) {
+    const text = JSON.stringify(json)
+    return new Promise((resolve, reject) => {
+      fs.writeFile(filePath, text, err => {
+        if (err) return reject(err)
+        // logger.log('WROTE:', json)
+        resolve()
+      })
+    })
+  }
+}
+
+module.exports = SDCard
diff --git a/src/models/sd-card.test.js b/src/models/sd-card.test.js
new file mode 100644
index 0000000..d6bbf00
--- /dev/null
+++ b/src/models/sd-card.test.js
@@ -0,0 +1,31 @@
+const fs = require('fs')
+const SDCard = require('./sd-card')
+
+jest.mock('fs')
+
+describe('models/sd-card', () => {
+  const filePath = '/path/to/cards.json'
+  const expected = [{ name: 'John', number: '123' }]
+
+  describe('.read', () => {
+    test('should read and convert file data to JSON', () => {
+      jest
+        .spyOn(fs, 'readFile')
+        .mockImplementationOnce((p, cb) => cb(null, JSON.stringify(expected)))
+      return SDCard.read(filePath).then(actual => {
+        expect(actual).toEqual(expected)
+      })
+    })
+  })
+
+  describe('.write', () => {
+    test('should write data to SD card', () => {
+      jest.spyOn(fs, 'writeFile').mockImplementationOnce((path, text, cb) => {
+        expect(path).toBe(filePath)
+        expect(text).toBe(JSON.stringify(expected))
+        cb()
+      })
+      return expect(SDCard.write(filePath, expected)).resolves.toBe()
+    })
+  })
+})