CODEWITHSUNDEEP
javascriptgoogle-chromebluetooth-lowenergy
Zwettekop
Zwettekop

Reputation: 93

The function writeValueWithoutResponse to write data to a BLE pheripheral doesn't exist

I'm trying to communicate via chrome with a BLE device and I'm following along with this video:

https://youtu.be/XDc5HUVMI5U?t=1023

Everything works until he says to use the method:

characteristic.writeValue(new Uint8Array[ 0x00,r, g,b ]);

I looked it up and it's deprecated: https://developer.mozilla.org/en-US/docs/Web/API/BluetoothRemoteGATTCharacteristic/writeValue

Instead you should use:

characteristic.writeValueWithoutResponse(new Uint8Array[ 0x00,r, g,b ]);

The problem is that this doesn't work either. It says:

script.js:29 Uncaught (in promise) TypeError: characteristic.writeValueWithoutResponse is not a function at HTMLButtonElement.setupBLE (script.js:29)

Does anyone know what I might be doing wrong? Here's all my code so far:

button.onclick = setupBLE;
let options = {
filters: [
{ services: ['19b10000-e8f2-537e-4f6c-d104768a1214'] },
{ name: 'Stepper motor control' }
]
};
async function setupBLE() {
console.log("test");
let device = await navigator.bluetooth.requestDevice(options);
let server = await device.gatt.connect();
let service = await server.getPrimaryService("19b10000-e8f2-537e-4f6c-d104768a1214");

//Same name but with 19b10001 instead of 19b10000
let characteristic = service.getCharacteristic("19b10001-e8f2-537e-4f6c-d104768a1214");
console.log(characteristic);
characteristic.writeValueWithoutResponse(new Uint8Array([0x00, 0x00, 0x00, 0x00]));
}```

Upvotes: 1

Views: 1388

Answers (1)

François Beaufort
François Beaufort

Reputation: 5629

As service.getCharacteristic() returns a promise, you have to use await there. Note that writeValueWithoutResponse also returns a promise.

const characteristicUuid = "19b10001-e8f2-537e-4f6c-d104768a1214";
const characteristic = await service.getCharacteristic(characteristicUuid);

const value = new Uint8Array([0x00, 0x00, 0x00, 0x00]);
await characteristic.writeValueWithoutResponse(value);

console.log("wrote value to characteristic");

You can find more documentation at https://web.dev/bluetooth/#write

Upvotes: 1

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