[英]chrome extension - reading from serial port
這是我第一次使用Chrome應用程序或擴展程序進行開發。 我在USB端口上有一個GPS接收器,它被模擬為串行設備。
運行此代碼
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);
在控制台中給我“/ dev / ttyUSB0”,所以它似乎找到了設備。
我如何連接到設備? 我已經在上面包含了serial.connect行,其中包含以下功能:
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;
}
}
};
但是我收到以下錯誤:
響應serial.connect時出錯:ReferenceError:_this沒有在Object.onGetDevices中定義[作為回調]
我不確定我在這里做的是對還是錯,所以任何指針都贊賞。
首先,該示例無法正常工作。 試試這個:
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);
});
});
現在,對於從串行連接實際讀取輸入,它將起作用,但將ArrayBuffer轉換為字符串比預期的要困難一些。
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