Reading USB Devices inside the Chrome App

Continuing our series of articles covering the development of BOLSHOI.

USB in der Arduino

We have this module successfully running our Hello World, now it is time to start digging data in an out of it from the controller.

And it reads beautifully

Selected and Voilá

Of course it could not open it, we're talking bootloader here and such :)

Base Code inside factory - AngularJS

app.service( 'usb', function( $rootScope, seed ) {

  this.getDevices = ()=>{

    var device_selector = document.getElementById('device-selector');
    var add_device = document.getElementById('add-device');
    var device_info = document.getElementById('device-info');

    var devices = {};

    function appendToDeviceSelector(device) {
      var el = document.createElement('option');
      el.setAttribute('value', device.device);
      el.textContent =
          'Product 0x' + ('0000' + device.productId.toString(16)).slice(-4) +
          ' Vendor 0x' + ('0000' + device.vendorId.toString(16)).slice(-4);
      device_selector.add(el);
    };

    function appendDeviceInfo(name, value) {
      var el = document.createElement('b');
      el.textContent = name + ': '
      device_info.appendChild(el);
      device_info.appendChild(document.createTextNode(value));
      device_info.appendChild(document.createElement('br'));
    }

    function populateDeviceInfo(handle, callback) {
      chrome.usb.getConfiguration(handle, function(config) {
        if (chrome.runtime.lastError != undefined) {
          var el = document.createElement('em');
          el.textContent = 'Failed to read device configuration: ' +
              chrome.runtime.lastError.message;
          device_info.appendChild(el);
        } else {
          var el = document.createElement('h2');
          el.textContent = 'Configuration ' + config.configurationValue;
          device_info.appendChild(el);

          for (var iface of config.interfaces) {
            el = document.createElement('h3');
            el.textContent = 'Interface ' + iface.interfaceNumber;
            device_info.appendChild(el);

            appendDeviceInfo('Alternate Setting', iface.alternateSetting);
            appendDeviceInfo('Inteface Class', iface.interfaceClass);
            appendDeviceInfo('Interface Subclass', iface.interfaceSubclass);
            appendDeviceInfo('Interface Protocol', iface.interfaceProtocol);

            for (var endpoint of iface.endpoints) {
              el = document.createElement('h4');
              el.textContent = 'Endpoint ' + endpoint.address;
              device_info.appendChild(el);

              appendDeviceInfo('Type', endpoint.type);
              appendDeviceInfo('Direction', endpoint.direction);
              appendDeviceInfo('Maximum Packet Size', endpoint.maximumPacketSize);
            }
          }
        }

        callback();
      });
    }

    function deviceSelectionChanged() {
      device_info.innerHTML = "";

      var index = device_selector.selectedIndex;
      if (index == -1) {
        var el = document.createElement('em');
        el.textContent = 'No device selected.';
        device_info.appendChild(el);
      } else {
        var device = devices[device_selector.options.item(index).value];

        appendDeviceInfo(
            'Product ID',
            '0x' + ('0000' + device.productId.toString(16)).slice(-4));
        appendDeviceInfo(
            'Vendor ID',
            '0x' + ('0000' + device.vendorId.toString(16)).slice(-4));

        chrome.usb.openDevice(device, function(handle) {
          if (chrome.runtime.lastError != undefined) {
            var el = document.createElement('em');
            el.textContent = 'Failed to open device: ' +
                chrome.runtime.lastError.message;
            device_info.appendChild(el);
          } else {
            populateDeviceInfo(handle, function () {
              chrome.usb.closeDevice(handle);
            });
          }
        });
      }
    }



    chrome.usb.getDevices({}, function(found_devices) {
      if (chrome.runtime.lastError != undefined) {
        console.warn('chrome.usb.getDevices error: ' +
                     chrome.runtime.lastError.message);
        return;
      }

      for (var device of found_devices) {
        devices[device.device] = device;
        appendToDeviceSelector(device);
      }
    });

    if (chrome.usb.onDeviceAdded) {
      chrome.usb.onDeviceAdded.addListener(function (device) {
        devices[device.device] = device;
        appendToDeviceSelector(device);
      });
    }

    if (chrome.usb.onDeviceRemoved) {
      chrome.usb.onDeviceRemoved.addListener(function (device) {
        delete devices[device.device];
        for (var i = 0; i < device_selector.length; ++i) {
          if (device_selector.options.item(i).value == device.device) {
            device_selector.remove(i);
            deviceSelectionChanged();
            break;
          }
        }
      });
    }

    add_device.addEventListener('click', function() {
      chrome.usb.getUserSelectedDevices({
        'multiple': false
      }, function(selected_devices) {
        if (chrome.runtime.lastError != undefined) {
          console.warn('chrome.usb.getUserSelectedDevices error: ' +
                       chrome.runtime.lastError.message);
          return;
        }

        for (var device of selected_devices) {
          var deviceInfo = { 'device': device, 'index': undefined };
          if (device.device in devices) {
            for (var i = 0; i < device_selector.length; ++i) {
              if (device_selector.options.item(i).value == device.device) {
                device_selector.selectedIndex = i;
                break;
              }
            }
          } else {
            devices[device.device] = device;
            appendToDeviceSelector(device);
            device_selector.selectedIndex = device_selector.options.length - 1;
          }
          deviceSelectionChanged();
        }
      });
    });

    device_selector.addEventListener('input', deviceSelectionChanged);

  };

});

EDUARDO CAPANEMA
HOLGER WILLING
ONUR METE
@bolshoi