Serial

Compatibility

• ✅ 2.2 | ✅ 2.1 | ⛔ 2.0 | ⛔ 1.9 | ...

Summary

Read and write data to a serial, parallel or virtual serial port.

List Serial Ports

qz.serial.findPorts().then(function(ports) {
   console.log(ports);
}).catch(displayError);

Open and Close Ports

• Open a serial port: openPort(port, bounds)

  var properties = {
     rx: {
        start: '\x02',
        end: '\x0D',
        width: null
     },
  
     baudRate: 9600,
     dataBits: 8,
     stopBits: 1,
     parity: 'NONE',
     flowControl: 'NONE'
  };
  
  // WARNING:  Since 2.0.7 baud properties should be set here in openPort()
  qz.serial.openPort('COM1', properties).then(function() { // or '/dev/ttyUSB0', etc
      console.log('COM1 opened');
  }).catch(function(err) {
      console.error(err);
  });

  • Note: For versions 2.0 and older, the properties syntax does not use the rx { } object, but instead uses start, end, width. Backwards support for the 2.0 syntax is deprecated in 2.1 versions.

• Close a serial port closePort(port)

  qz.serial.closePort('COM1').then(function() {  // or '/dev/ttyUSB0', etc
      console.log('COM1 closed');
  }).catch(function(err) {
      console.error(err);
  });

Send String Data

• Send data to the open serial port via sendData(port, data, properties)

  Note: The default sendData() settings must be changed for Mettler Toledo scales

  var data = 'hi, serial port\n'; // or since 2.1.1: { type: 'plain', data: '...' }
  
  // WARNING:  sendData() properties are deprecated in 2.0.7.  Baud properties should be set in openPort() instead.
  qz.serial.sendData('COM1', data).catch(displayError);

Send Hex Data

Since 2.1.1

• Send data to the open serial port via sendData(port, data, properties)

  var data = {
     type: 'hex',
     data: 'x68x65x6Cx6Cx6Fx0A' // 'hello\n'
  };
  
  qz.serial.sendData('COM1', data).catch(displayError);

Send File Data

Since 2.1.1

• Send data to the open serial port via sendData(port, data, properties)

  var data = {
     type: 'file',
     data: 'mydirectory/myfile.txt'
  };
  
  qz.serial.sendData('COM1', data).catch(displayError);

Send Base64 Data

Since 2.1.1

• Send data to the open serial port via sendData(port, data, properties)

  var data = {
     type: 'base64',
     data: 'aGVsbG8K' // 'hello\n'
  };
  
  qz.serial.sendData('COM1', data).catch(displayError);

Mettler Toledo

The default settings need to be changed for serial communication to work with Mettler Toledo scales. For other scale types, see issue #1158.

var data = 'W\n';   // <--- Weight command - Also works with 'W\r'

var properties = {
   // ...

   baudRate: 9600,
   dataBits: 7,     // <--- Changed from 8
   stopBits: 1,
   parity: 'EVEN',  // <--- Changed from NONE
   flowControl: 'NONE'
};

// WARNING:  sendData() properties are deprecated in 2.0.7.  Baud properties should be set in openPort() instead.
qz.serial.sendData('COM1', data, properties).catch(displayError);

Process Results

1. Use a callback for processing the data returned from the serial port.

   qz.serial.setSerialCallbacks(function(evt) {
      if (evt.type !== 'ERROR') {
         console.log('Serial', evt.portName, 'received output', evt.output);
      } else {
         console.error(evt.exception);
      }
   });

Troubleshooting

Linux Permission Denied

If no ports will list or if you receive Permission denied in Linux (bugs.launchpad.net#949597)

Error: Port name - /dev/ttyUSB0; Method name - openPort(); Exception type - Permission denied.

1. Run the following command:

   sudo usermod -a -G dialout "$USER"

2. Log out of the desktop (or reboot)

3. Log in to the desktop, try again