> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rebellapp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# my.writeBLECharacteristicValue

> Write a value to a BLE device characteristic.

Use this API to write data to a characteristic on a connected BLE device. The target characteristic must support writing.

## Parameters

| Property         | Type       | Required | Description                                            |
| ---------------- | ---------- | -------- | ------------------------------------------------------ |
| deviceId         | String     | Yes      | Device identifier                                      |
| serviceId        | String     | Yes      | Service UUID                                           |
| characteristicId | String     | Yes      | Characteristic UUID                                    |
| value            | Hex String | Yes      | Hexadecimal string value to write, limited to 20 bytes |
| success          | Function   | No       | Callback on success                                    |
| fail             | Function   | No       | Callback on failure                                    |
| complete         | Function   | No       | Callback that always executes                          |

## Code Example

```javascript theme={null}
my.writeBLECharacteristicValue({
  deviceId: 'XX:XX:XX:XX:XX:XX',
  serviceId: '0000FFF0-0000-1000-8000-00805F9B34FB',
  characteristicId: '0000FFF1-0000-1000-8000-00805F9B34FB',
  value: 'fffe',
  success: (res) => {
    console.log('Write succeeded:', res);
  },
  fail: (err) => {
    console.error('Write failed:', err);
  }
});
```

## Error Codes

| Code  | Description                                                           |
| ----- | --------------------------------------------------------------------- |
| 10000 | The Bluetooth adapter is not initialized                              |
| 10001 | The Bluetooth adapter is not available                                |
| 10002 | Device not found                                                      |
| 10003 | Connection failed                                                     |
| 10004 | Service not found                                                     |
| 10005 | Characteristic not found                                              |
| 10006 | Connection lost                                                       |
| 10007 | Characteristic not supported                                          |
| 10008 | System error                                                          |
| 10009 | BLE is not supported for Android systems with versions lower than 4.3 |
| 10011 | Invalid device ID                                                     |
| 10012 | Invalid service ID                                                    |
| 10013 | Invalid characteristic ID                                             |
| 10014 | Invalid data                                                          |
| 10015 | Timeout                                                               |
| 10016 | Parameters not enough                                                 |
| 10017 | Failed to write characteristic                                        |

<Warning>
  IDE simulation is not supported for this API. Test on a real device.
</Warning>

## Related APIs

<CardGroup cols={2}>
  <Card title="my.readBLECharacteristicValue" icon="arrow-down" href="/jsapi/device/bluetooth/my.readBLECharacteristicValue">
    Read a characteristic value
  </Card>

  <Card title="my.onBLECharacteristicValueChange" icon="bell" href="/jsapi/device/bluetooth/my.onBLECharacteristicValueChange">
    Listen for value changes
  </Card>
</CardGroup>