digispark + node.js + google gmail api; notify unread message of gmail as digispark led blinking; http://actinium.org/electronics/avr/digispark/

app.js

var usb = require('usb');
var fs = require('fs');
var readline = require('readline');
var google = require('googleapis');
var googleAuth = require('google-auth-library');

// const
var USBRQ_HID_SET_REPORT = 0x09;
var USB_HID_REPORT_TYPE_FEATURE = 0x03;

// define; default of digispark hid
var VID = 0x16c0;
var PID = 0x05df;

var sendDigispark = function (data, callback) {
    if (typeof callback !== 'function') {
        callback = function () {};
    }
    // search device
    var device = usb.findByIds(VID, PID);
    if (device) {
        try {
            // open device
            device.open();
            
            // send
            var reportId = 0, len = 1;
            device.controlTransfer(
                // bmRequestType
                usb.LIBUSB_REQUEST_TYPE_CLASS | usb.LIBUSB_RECIPIENT_DEVICE | usb.LIBUSB_ENDPOINT_OUT,
                // bRequest
                USBRQ_HID_SET_REPORT,
                // wValue
                (USB_HID_REPORT_TYPE_FEATURE << 8) | reportId,
                // wIndex
                data,
                // data_or_length
                new Buffer(len),
                function (err) {
                    // end
                    device.close();
                    callback(err);
                }
            );
        } catch (e) {
            device.close();
            callback(e);
        }
    } else {
        callback(new Error('Device not found.'));
    }
};

//
// from https://developers.google.com/gmail/api/quickstart/nodejs#step_3_set_up_the_sample
//

// If modifying these scopes, delete your previously saved credentials
// at ~/.credentials/gmail-nodejs-quickstart.json
var SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];
//var TOKEN_DIR = (process.env.HOME || process.env.HOMEPATH ||
//    process.env.USERPROFILE) + '/.credentials/';
var TOKEN_DIR = process.cwd() + '/.credentials/';
var TOKEN_PATH = TOKEN_DIR + 'gmail-nodejs-quickstart.json';

// Load client secrets from a local file.
fs.readFile('client_secret.json', function processClientSecrets(err, content) {
  if (err) {
    console.log('Error loading client secret file: ' + err);
    return;
  }
  // Authorize a client with the loaded credentials, then call the
  // Gmail API.
  authorize(JSON.parse(content), main);
});

/**
 * Create an OAuth2 client with the given credentials, and then execute the
 * given callback function.
 *
 * @param {Object} credentials The authorization client credentials.
 * @param {function} callback The callback to call with the authorized client.
 */
function authorize(credentials, callback) {
  var clientSecret = credentials.installed.client_secret;
  var clientId = credentials.installed.client_id;
  var redirectUrl = credentials.installed.redirect_uris[0];
  var auth = new googleAuth();
  var oauth2Client = new auth.OAuth2(clientId, clientSecret, redirectUrl);

  // Check if we have previously stored a token.
  fs.readFile(TOKEN_PATH, function(err, token) {
    if (err) {
      getNewToken(oauth2Client, callback);
    } else {
      oauth2Client.credentials = JSON.parse(token);
      callback(oauth2Client);
    }
  });
}

/**
 * Get and store new token after prompting for user authorization, and then
 * execute the given callback with the authorized OAuth2 client.
 *
 * @param {google.auth.OAuth2} oauth2Client The OAuth2 client to get token for.
 * @param {getEventsCallback} callback The callback to call with the authorized
 *     client.
 */
function getNewToken(oauth2Client, callback) {
  var authUrl = oauth2Client.generateAuthUrl({
    access_type: 'offline',
    scope: SCOPES
  });
  console.log('Authorize this app by visiting this url: ', authUrl);
  var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
  });
  rl.question('Enter the code from that page here: ', function(code) {
    rl.close();
    oauth2Client.getToken(code, function(err, token) {
      if (err) {
        console.log('Error while trying to retrieve access token', err);
        return;
      }
      oauth2Client.credentials = token;
      storeToken(token);
      callback(oauth2Client);
    });
  });
}

/**
 * Store token to disk be used in later program executions.
 *
 * @param {Object} token The token to store to disk.
 */
function storeToken(token) {
  try {
    fs.mkdirSync(TOKEN_DIR);
  } catch (err) {
    if (err.code != 'EEXIST') {
      throw err;
    }
  }
  fs.writeFile(TOKEN_PATH, JSON.stringify(token));
  console.log('Token stored to ' + TOKEN_PATH);
}


//
// user application
//

// loop process
var tick = function () {
    // gmail get unread message list
    google.gmail('v1').users.messages.list({
        userId: 'me',
        q: 'is:unread',
    }, function (err, res) {
        // if unread message exists
        if (!err && res && res.messages && res.messages.length) {
            sendDigispark(1);// gmail blink mode
        } else {
            sendDigispark(0);// no blink
        }
    });
};

// setup user application
var main = function (auth) {
    // set auth as a global default
    google.options({auth: auth});
    
    // start service
    var f = function () {
        tick();
        setTimeout(f, 10 * 1000);// check interval[ms]
    };
    
    // init
    f();
};

digispark.ino

#include <DigiUSB.h>

#define LED_PORT 1

void setup() {
    DigiUSB.begin();
    pinMode(LED_PORT, OUTPUT);
}

int blinkMode = 0;

void loop() {
    if (DigiUSB.available()) {
        blinkMode = DigiUSB.read();
    }
    switch (blinkMode) {
        // no blink
        case 0:
            digitalWrite(LED_PORT, LOW);
            break;
        // gmail unread
        case 1:
            for (int i = 0; i < 3; i++) {
                digitalWrite(LED_PORT, HIGH);
                DigiUSB.delay(100);
                digitalWrite(LED_PORT, LOW);
                DigiUSB.delay(100);
            }
            DigiUSB.delay(500);
            break;
    }
    DigiUSB.refresh();
}