Chrome扩展程序无法找到USB打印机设备

Question

我正在为POS终端打印机构建chrome应用程序。我的问题是由于某种原因chrome应用程序找不到USB设备，我不知道为什么它不起作用。我尝试了几种方法（将十六进制供应商/产品ID转换为十进制，使用十六进制产品/供应商ID连接到USB打印机）以及无法找到设备的所有报告...

修改

我从设备日志中收到此错误：

 Failed to open device: Operation not supported or unimplemented on this platform

有人知道问题出在哪里吗？

以下是有关打印机（DATECS DPP 255）的详细信息：

清单：

{


 "manifest_version": 2,

  "name": "Thermal Printer Extension",
  "description": "Thermal Printer Extension for ESC/POS Commands",
  "version": "1.0",
  "app": {
    "background": {
      "scripts": ["main.js"]
    }
  },
  "permissions": ["usb", "notifications"],
  "optional_permissions": [
    {
      "usbDevices": [
        {
          "vendorId": 65520, "productId": 98
        }
      ]
    }
  ],
  "externally_connectable": {
    "matches": ["http://localhost:3000/*"]
  }
}

main.js

chrome.runtime.onMessageExternal.addListener(function (stuff) {
if(stuff){
    function pad(n, width, z) {
        z = z || '0';
        n = n + '';
        return n.length >= width ? n : new Array(width - n.length + 1).join(z) + n;
    }
    var port = 0;
    var endpoint = 0x01;

    // needs to be set in optional permissions for each VID/PID pair
    var device = {vendorId: 0xfff0, productId: 0x0062};
   // var device = {vendorId: 65520, productId: 98};

    String.prototype.toBytes = function() { 
        var arr = [];
        for (var i=0; i < this.length; i++) { 
            arr.push(this[i].charCodeAt(0));
        } 
        return arr; 
    }

    // setting variables for printing, array for data, and calculations
    var alignLeft = [0x01B, 0x061, 0];
    var alignCenter = [0x01B, 0x061, 1];
    var alignRight = [0x01B, 0x061, 2];
    var endPrint = [0x01B, 0x064, 2];
    // enter new line
    var lineFeed = [0x00A];
    var buzz = [07];
    var drawLineMiddle = "________________________________________________".toBytes();
    var drawLineSmall = "________________________________".toBytes();
    var horizontalTab = [0x009];
    var cutpaperFull = [0x01D, 0x056, 1];
    var cutpaperPartial = [0x01D, 0x056, 0];

    function createAnything() {
        var anything = alignCenter;
        anything = anything.concat("Awesome Chrome Extension".toBytes());
        anything = anything.concat(lineFeed);
        anything = anything.concat(drawLineMiddle);
        anything = anything.concat(stuff.stuffToPrint.toBytes());
        anything = anything.concat(lineFeed);
        return anything;
    }

    function createReceipt(devices) {
        var data = [];
        data = data.concat(createAnything());
        data = data.concat(endPrint);
        data = data.concat(cutpaperPartial);
        var buffer = new Uint8Array(data).buffer;
        var transferinfo = {direction: "out", endpoint: endpoint, data: buffer };
        chrome.usb.bulkTransfer({handle: devices[0].handle, vendorId: devices[0].vendorId, productId: devices[0].productId}, transferinfo, function(response) {
            if (response.resultCode == 0) {
                chrome.usb.closeDevice({handle: devices[0].handle, vendorId: devices[0].vendorId, productId: devices[0].productId}, chrome.notifications.create("4", {type: "basic", iconUrl: "icon.png", title: "Success!", message: "Printing receipt..."}, function() {console.log("Success!")}));
            } else {
                console.log("Error ", response);
            } 
        });
    }

    var connect = function(callback) {
        chrome.permissions.getAll(function(p) {
            if (p.permissions.indexOf("usb") >= 0) {
                //construct permission object for our device
                var obj = { usbDevices: [device] };
                //now request the permissions
                chrome.permissions.request({ permissions: [obj] }, function(granted) {
                    if (granted) {
                        chrome.usb.findDevices(device, function(devices) {
                            if (devices && devices.length > 0) {
                                //use the first found device
                                var foundDevice = devices[0];
                                //now lets reset the device
                                chrome.usb.resetDevice(foundDevice, function() {
                                    //perform some error checking to make sure we reset the device
                                    if ( ! chrome.runtime.lastError) {
                                        //now claim the interface using the port we specified
                                        chrome.usb.claimInterface(foundDevice, port, function() {
                                        if ( ! chrome.runtime.lastError) {
                                            callback(devices);
                                        } else {
                                            throw chrome.runtime.lastError.message;    
                                        } 
                                        });
                                    } else {
                                        throw chrome.runtime.lastError.message;
                                    }
                                });
                            } else {
                                chrome.notifications.create("1", {type: "basic", iconUrl: "icon.png", title: "Error", message: "Device not found!"}, function() {console.warn("Device not found!")});
                                console.warn("Device not found!");
                            }
                        });
                    } else {
                        chrome.notifications.create("2", {type: "basic", iconUrl: "icon.png", title: "Error", message: "USB Permission not granted."}, function() {console.warn("USB Permission not granted.")});
                        console.warn("USB Permission not granted.");
                    }
                });
            } else {
                chrome.notifications.create("3", {type: "basic", iconUrl: "icon.png", title: "Error", message: "No USB permissions granted."}, function() {console.warn("No USB permissions granted.")});
                console.warn("No USB permissions granted.");
            }
        });
    }
    connect(createReceipt);
}
});