2.0 USB Communication

Read Data

• Claims device based on hardware information
• Reads data from device
• Releases device

// Hardware info (modify to match hardware)
var usb = {
   vendor: '0x0EB8',
   product: '0xF000',
   device: '0x00',
   endpoint: '0x81'
};

// Generic error handler
var err = function(e) { console.error(e); }

// Generic data handler
var process = function(data) { console.log(data); }

// Handler to release claimed device	
var release = function() {
   qz.usb.releaseDevice(usb.vendor, usb.product).catch(err);
}

// Connect to QZ Tray, claim, read, release
qz.websocket.connect().then(function() {
   return qz.usb.claimDevice(usb.vendor, usb.product, usb.device);
}).catch(err).then(function() {
   return qz.usb.readData(usb.vendor, usb.product, usb.endpoint, '8');
}).then(process).then(release);

Send Data

• FIXME

// 

USB Scale

• Parses data returned from USB port to determine status, weight, units and precision. Compatible with most USB attached scales (Stamps.com, Mettler Toledo, Dymo, etc).
• Requires read data example above.

var process = function(data) {
   // Get status
   var status = parseInt(data[1], 16);
   switch(status) {
      case 1:	// fault
      case 5:	// underweight
      case 6:	// overweight
      case 7:	// calibrate
      case 8:	// re-zero
         status = 'error'; break;
      case 3:
         status = 'busy'; break;
      case 2:	// stable at zero
      case 4: // stable non-zero
      default:
         status = 'stable';
   }
		
   // Get precision
   var precision = parseInt(data[3], 16);
   precision = precision ^ -256; // unsigned to signed

   // Get units
   var units = parseInt(data[2], 16);
   switch(units) {
      case 3:
         units = 'kg'; break;
      case 11:
         units = 'oz'; break;
      case 12:
      default:
	 units = 'lbs';
   }

   // Get weight
   data.splice(0,4);
   data.reverse();
   weight = parseInt(data.join(''), 16);
		
   // Apply precision
   weight *= Math.pow(10, precision);
   weight = weight.toFixed(Math.abs(precision));

   // Log data to the console
   console.log(status + ": " + weight + units);
}