Implements multiple printers for the USB adapter, updates readme to e…

…xplain how to use it

README.md

@@ -12,9 +12,9 @@ $ npm i escpos
 
 if you use usb as an adapter :
 
-+ On Linux, you'll need `libudev` to build libusb. 
++ On Linux, you'll need `libudev` to build libusb.
 + On Ubuntu/Debian: `sudo apt-get install build-essential libudev-dev`.
-+ On Windows, Use [Zadig](http://sourceforge.net/projects/libwdi/files/zadig/) to install the WinUSB driver for your USB device. 
++ On Windows, Use [Zadig](http://sourceforge.net/projects/libwdi/files/zadig/) to install the WinUSB driver for your USB device.
 
 Otherwise you will get `LIBUSB_ERROR_NOT_SUPPORTED` when attempting to open devices.
 
@@ -23,6 +23,7 @@ Otherwise you will get `LIBUSB_ERROR_NOT_SUPPORTED` when attempting to open devi
 ````javascript
 const escpos = require('escpos');
 
+// Select the adapter based on your printer type
 const device  = new escpos.USB();
 // const device  = new escpos.Network('localhost');
 // const device  = new escpos.Serial('/dev/usb/lp0');
@@ -48,8 +49,37 @@ device.open(function(){
 
 
 ````
+----
+## USB Adapter methods
+### open(function calback)
+Claims the current device USB, if the printer is already in use by other process this will fail.
 
-## Documentation
+By default, the USB adapter will set the first printer found, if you have multiple printers use `setDevice` and `getDevices` to switch between printers.
+
+Triggers the callback function when done.
+
+### openAll()
+Claims all the printers connected to the machine, one by one. When done, sets the first printer found as the default device and triggers the callback function.
+
+### getDevices()
+Returns the number (N) of printers connected, if open is called you must open each device in order to use it.
+
+The ID of the printer will be the number you want to set from 0 to N-1.
+
+### setDevice(N)
+Sets the index passed as the current device, N must be higher than 0 and lower than `getDevices()`.
+
+This must be called before printing if you want to swtich between multiple printers connected to the same device.
+
+### close(function callback)
+Closes the current device and releases its USB interface.
+
+### closeAll(function callback)
+Similar to `close()` but loops through all the devices connected and closes them all.
+
+----
+
+## Printer methods
 
 Escpos inherits its methods to the printers. the following methods are defined:
 
@@ -133,12 +163,16 @@ Partial cut is not implemented in all printers.
 Sends a pulse to the cash drawer in the specified pin.
 
 pin is a numeric value which defines the pin to be used to send the pulse, it could be 2 or 5.
-Raises CashDrawerError()
+Raises `CashDrawerError()``
+
+----
 
 ## Thanks
 
 + Part of code from [@taoyuan](https://github.com/taoyuan)
 
+----
+
 ## Contributing
 - Fork this repo
 - Clone your repo
@@ -148,6 +182,8 @@ Raises CashDrawerError()
 - Make sure your features are fully tested
 - Open a pull request, and enjoy <3
 
+----
+
 ### MIT license
 Copyright (c) 2015 lsong
 

adapter/usb.js

@@ -23,32 +23,46 @@ const IFACE_CLASS = {
  */
 function USB(vid, pid){
   var self = this;
+
+  this.device = null;
+  this.devices = [];
+
   if(vid && pid){
-    this.device = usb.findByIds(vid, pid);
+    this.devices = [usb.findByIds(vid, pid)];
+    this.device = this.devices[0];
   }else{
-    this.device = USB.findPrinter();
+    this.findPrinter();
   }
-  
+
   if (!this.device)
     throw new Error('Can not find printer');
-  
+
   usb.on('detach', function(device){
-    if(device == self.device){
-      self.emit('detach'    , device);
-      self.emit('disconnect', device);
-      self.device = null;
+    self.emit('detach'    , device);
+    self.emit('disconnect', device);
+
+    for(let i in self.devices) {
+      if(device == self.devices[i]) {
+        self.devices.splice(i, 1);
+      }
+    }
+
+    if(device == self.device) {
+      if(self.devices.length > 0) {
+        self.device = self.devices[0];
+      } else self.device = null;
     }
   });
-  EventEmitter.call(this);  
+  EventEmitter.call(this);
   return this;
 };
 
 /**
  * [findPrinter description]
  * @return {[type]} [description]
  */
-USB.findPrinter = function(){
-  return usb.getDeviceList().filter(function(device){
+USB.prototype.findPrinter = function(){
+  this.devices = usb.getDeviceList().filter(function(device){
     try{
       return device.configDescriptor.interfaces.filter(function(iface){
         return iface.filter(function(conf){
@@ -58,7 +72,12 @@ USB.findPrinter = function(){
     }catch(e){
       return false;
     }
-  })[0];
+  });
+
+  if(this.devices.length > 0) {
+    // Select first printer found by default
+    this.device = this.devices[0];
+  }
 };
 
 /**
@@ -71,28 +90,74 @@ util.inherits(USB, EventEmitter);
  * @param  {Function} callback [description]
  * @return {[type]}            [description]
  */
-USB.prototype.open = function (callback){
-  var self = this, counter = 0;
+USB.prototype.open = function (callback, i){
+  let self = this, counter = 0, index = i || 0;
   this.device.open();
   this.device.interfaces.forEach(function(iface){
     (function(iface){
       iface.setAltSetting(iface.altSetting, function(){
         iface.claim(); // must be called before using any endpoints of this interface.
         iface.endpoints.filter(function(endpoint){
-          if(endpoint.direction == 'out' && !self.endpoint){
+          if(endpoint.direction == 'out' && !self.endpoint) {
             self.endpoint = endpoint;
-            self.emit('connect', self.device);
-            callback && callback(null, self);  
+            self.devices[index]._endpoint = endpoint; // store each endpoint for later
           }
         });
-        if(++counter === this.device.interfaces.length && !self.endpoint){
+
+        if(self.endpoint) {
+          self.emit('connect', self.device);
+          callback && callback(null, self);
+        } else if(++counter === this.device.interfaces.length && !self.endpoint){
           callback && callback(new Error('Can not find endpoint from printer'));
         }
       });
     })(iface);
   });
+
+  return this;
+};
+
+USB.prototype.openAll = function (callback) {
+  this.openNext(0, callback);
+  return this;
+};
+
+USB.prototype.openNext = function(index, callback) {
+  let self = this;
+
+  this.setDevice(index).open(function(err) {
+    if(err) {
+      console.log(err);
+      return;
+    }
+
+    if((index+1) == self.devices.length) {
+      callback && callback(null);
+    } else {
+      self.openNext(index+1, callback);
+    }
+  }, index);
+
+  return this;
+}
+
+USB.prototype.setDevice = function(i) {
+  if(this.devices[i]) {
+    this.device = this.devices[i];
+    if('_endpoint' in this.device) {
+      this.endpoint = this.device._endpoint;
+    } else {
+      this.endpoint = null;
+    }
+  }
+
   return this;
 };
+
+USB.prototype.getDevices = function() {
+  return this.devices.length;
+};
+
 /**
  * [function write]
  * @param  {[type]} data [description]
@@ -109,6 +174,27 @@ USB.prototype.close = function(callback){
   return this;
 };
 
+USB.prototype.closeAll = function(callback){
+  let self = this;
+  self.closeNext(0, callback);
+  return this;
+};
+
+USB.prototype.closeNext = function(index, callback) {
+  let self = this;
+
+  self.setDevice(index).close(function() {
+    self.devices.splice(index, 1);
+    if(self.devices.length == 0) {
+      callback && callback(null);
+    } else {
+      self.closeNext(0, callback);
+    }
+  });
+
+  return this;
+}
+
 /**
  * [exports description]
  * @type {[type]}

examples/multiple_usb.js

@@ -0,0 +1,23 @@
+'use strict';
+const escpos = require('../');
+
+const device  = new escpos.USB();
+const printer = new escpos.Printer(device);
+
+device.openAll(function(){
+  let devices = device.getDevices();
+
+  for(let i = 0; i < devices; i++) {
+    console.log('Printing on device', (i+1));
+    setTimeout(function() {
+      device.setDevice(i);
+      printer.font('a')
+             .align('ct')
+             .style('bu')
+             .size(1, 1)
+             .text('This is the printer #' + (i+1))
+             .cut();
+    }, 500*i);
+  }
+
+});

package.json

@@ -1,6 +1,6 @@
 {
   "name": "escpos",
-  "version": "2.3.0",
+  "version": "2.3.1",
   "description": "ESC/POS Printer driver for nodejs",
   "main": "index.js",
   "scripts": {