javascript chrome 扩展 - 从串口读取
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chrome extension - reading from serial port
提问by Joe Kasavage
This is my first attempt at developing with a chrome app or extension. I have a GPS receiver on the USB port which is emulated as a serial device.
这是我第一次尝试使用 chrome 应用程序或扩展程序进行开发。我在 USB 端口上有一个 GPS 接收器，它被模拟为串行设备。
Running this code
运行此代码
var onGetDevices = function(ports) {
for (var i=0; i<ports.length; i++) {
// show me some output
console.log(ports[i].path);
// Connect to the serial port /dev/ttyUSB0
chrome.serial.connect(ports[i].path, {bitrate: 9600}, onConnect);
}
}
chrome.serial.getDevices(onGetDevices);
gets me "/dev/ttyUSB0" in the console, so it appears to be finding the device.
在控制台中让我“/dev/ttyUSB0”，所以它似乎正在寻找设备。
How do I then connect to the device? I've included the serial.connect line above, with the following functions:
然后我如何连接到设备？我已经包含了上面的 serial.connect 行，具有以下功能：
var onConnect = function(connectionInfo) {
// The serial port has been opened. Save its id to use later.
_this.connectionId = connectionInfo.connectionId;
// Do whatever you need to do with the opened port.
chrome.serial.onReceive.addListener(onReceiveCallback);
}
var stringReceived = '';
var onReceiveCallback = function(info) {
if (info.connectionId == expectedConnectionId && info.data) {
var str = convertArrayBufferToString(info.data);
if (str.charAt(str.length-1) === '\n') {
stringReceived += str.substring(0, str.length-1);
onLineReceived(stringReceived);
stringReceived = '';
}
else {
stringReceived += str;
}
}
};
but I get the following error:
但我收到以下错误：
Error in response to serial.connect: ReferenceError: _this is not defined at Object.onGetDevices [as callback]
响应 serial.connect 时出错：ReferenceError: _this is not defined at Object.onGetDevices [as callback]
I'm not sure exactly what I'm doing right or wrong here so any pointers appreciated.
我不确定我在这里做对了还是做错了，所以任何指示都表示赞赏。
回答by Joe Kasavage
First the example does not work properly. Try this instead:
首先，示例无法正常工作。试试这个：
var connectionId;
$(document).ready(function() {
chrome.serial.getDevices(function(devices) {
for (var i = 0; i < devices.length; i++) {
$('select#portList').append('<option value="' + devices[i].path + '">' + devices[i].path + '</option>');
}
});
// ui hook
$('button#open').click(function() {
var clicks = $(this).data('clicks');
if (!clicks) {
var port = $('select#portList').val();
chrome.serial.connect(port, {bitrate: 9600}, function(info) {
connectionId = info.connectionId;
$("button#open").html("Close Port");
console.log('Connection opened with id: ' + connectionId + ', Bitrate: ' + info.bitrate);
});
} else {
chrome.serial.disconnect(connectionId, function(result) {
$("button#open").html("Open Port");
console.log('Connection with id: ' + connectionId + ' closed');
});
}
$(this).data("clicks", !clicks);
});
});
Now as for the actual reading of the input from the serial connection it will work but converting the ArrayBuffer to a string is a bit harder than expected.
现在至于从串行连接实际读取输入它会工作，但将 ArrayBuffer 转换为字符串比预期的要困难一些。
