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index.js
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index.js
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var usb = require('usb'),
events = require('events'),
async = require('async'),
Scale;
Scale = function() {
var that = this,
status = false;
events.EventEmitter.call(this);
this.vendorId = 2338;
this.weight = {
value: 0,
overweight: false,
system: undefined,
};
this.connect = function(productId, device) {
async.waterfall([
function(callback) {
var devicesFound = [],
devices,
i, ii;
if (device) {
// A device was already provided, no need to scan for it
callback(null, device);
return;
}
if (productId && usb.findByIds(that.vendorId, productId)) {
// The productId is a valid one, move along
callback(null, usb.findByIds(that.vendorId, productId));
} else {
// .connect() wasn't passed a productId, attempt to find it
devices = usb.getDeviceList();
for (i=0,ii=devices.length;i<ii;i++) {
// Scan all USB devices to see if there's a hit
if (devices[i].deviceDescriptor.idVendor === that.vendorId) {
devicesFound.push(devices[i]);
}
}
if (devicesFound.length > 1) {
// For now, we can only have one scale plugged in
callback('There is more than one Dymo scale connected. A productId is required.');
} else if (devicesFound.length === 0) {
// No scales were found
callback('No USB scale detected');
} else {
// Exactly one valid scale was found. Good!
callback(null, devicesFound[0]);
}
}
},
function(device, callback) {
device.open();
device.reset(function() {
if (device.interface(0).isKernelDriverActive()) {
device.interface(0).detachKernelDriver();
}
device.interface(0).claim();
callback(null, device);
});
},
function(device, callback) {
device.interface(0).endpoint(130).startPoll(3,6);
status = true;
device.interface(0).endpoint(130).on('error', function(data) {
status = false;
that.emit('end');
callback(data);
});
device.interface(0).endpoint(130).on('end', function(data) {
status = false;
that.emit('end');
device.interface(0).endpoint(130).stopPoll();
callback(data);
});
device.interface(0).endpoint(130).on('data', function(data) {
var dataArray = data.toJSON(),
change = false,
value = 0,
overweight = false,
system = 'ounces';
if (dataArray[1] === 2) {
// no weight is on the scale
value = 0;
overweight = false;
}
if (dataArray[2] == 11) {
system = 'ounces';
}
if (dataArray[2] == 2) {
system = 'grams';
}
if (dataArray[1] === 4 && system === 'ounces') {
overweight = false;
value = Math.round(((dataArray[4] + (dataArray[5] * 256)) * 0.1) * 10) / 10;
}
if (dataArray[1] === 4 && system === 'grams') {
overweight = false;
value = Math.round((dataArray[4] + dataArray[5] * 256) * 10) / 10;
}
if (dataArray[1] === 6) {
// there's too much weight
value = 0;
overweight = true;
}
if (that.weight.value !== value) {
that.weight.value = value;
that.weight.system = system;
that.emit('weight-change', { value: value, system: system });
change = true;
}
if (that.weight.overweight !== overweight) {
that.weight.overweight = overweight;
that.emit('overweight-change', overweight);
change = true;
}
if (change === true) {
that.emit('weight', that.weight);
}
});
}
], function(err, result) {
if (err) {
// TODO: do something to handle errors
}
});
};
this.getWeight = function() {
return {
value: this.weight.value,
system: this.weight.system
}
};
this.getOverweightStatus = function() {
return this.weight.overweight;
};
this.getStatus = function() {
return status;
};
usb.on('attach', function(device) {
// A new USB device was attached/powered on, check to see if it's a scale
if (device.deviceDescriptor.idVendor === that.vendorId) {
that.connect(null, device);
that.emit('online');
}
})
usb.on('detach', function(device) {
// A device was detached. See if it's our scale
if (device.deviceDescriptor.idVendor === that.vendorId) {
status = false;
that.emit('offline');
}
})
};
Scale.prototype.__proto__ = events.EventEmitter.prototype;
module.exports = new Scale();