CODEWITHSUNDEEP
javascriptgoogle-chromebluetoothweb-bluetooth
Wezley
Wezley

Reputation: 413

WebBluetooth Failing a Write Characteristic on Windows but not OSX

I'm trying to send a sample hex string to a BLE device via web bluetooth.

This string is sending perfectly fine on OSX, but when I attempt to send it on windows I'm getting the following error:

Uncaught (in promise) DOMException: GATT operation failed for unknown reason.

Here is the code I'm using to send the string and convert it:

        event.target.writeValue(str2ab(":100000000C9434000C943E000C943E000C943E0082*"));

Here is my str2ab function:

 function str2ab(str) {
  var buf = new ArrayBuffer(str.length*2); // 2 bytes for each char
  var bufView = new Uint16Array(buf);
  for (var i=0, strLen=str.length; i<strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}

Upvotes: 2

Views: 1018

Answers (1)

Wezley
Wezley

Reputation: 413

So it looks like for windows you have a 20 byte limit.

To correct the issue I'm using a write buffer and recursively going over it until all the bites have been written. Here is the code.

function writeBuffer(string) {
  writeOut(string, 0);
}

function writeOut(string, start) {
  if(start >= string.length) return;
  myCharacteristic.writeValue(str2ab(string.substring(start, (start+20)))).then(foo => {
    writeOut(string, (start+20));
  });
}

Upvotes: 1

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