What's the nRF Connect data format when writing chraracteristics ?

RE: What's the nRF Connect data format when writing chraracteristics ?

flexbox — Mon, 01 Jul 2024 10:36:45 GMT

Thanks for the explanations Aleksander 🙌

Following your advice I try to get returned values without any success

one case is always null

 const result = await BLEService.writeCharacteristicWithoutResponseForDevice(
   SPP_SERVICE_UUID,
   SPP_CHARACTERISTIC_UUID, // characteristic UUID read and write
   valueToWrite // sends as byte array.
 );

 // Result is always null
 // {
 //   deviceID: "71511EB2-XXXX-XXXX-XXXX-77B2FAC78495"
 //   id: 12928767904
 //   isIndicatable: false
 //   isNotifiable: false
 //   isNotifying: false
 //   isReadable: true
 //   isWritableWithResponse: false
 //   isWritableWithoutResponse: true
 //   serviceID: 12909164416
 //   serviceUUID: "0c6b000a-2f43-7eb4-0646-e5c28162cf6c"
 //   uuid: "0c6b000c-2f43-7eb4-0646-e5c28162cf6c"
 //   value: null
 //  }

the other one is an error

 const result = await BLEService.writeCharacteristicWithResponseForDevice(
   SPP_SERVICE_UUID,
   SPP_CHARACTERISTIC_UUID, // characteristic UUID read and write
  valueToWrite // sends as byte array.
 );
 // return an error
 // ❌ ~ showErrorToast: {
 //   "message": "Characteristic 0c6b000c-2f43-7eb4-0646-e5c28162cf6c write failed for device 71511EB2-D2BC-D5F8-4DF7-77B2FAC78495 and service 0c6b000a-2f43-7eb4-0646-e5c28162cf6c",
 //   "errorCode": 401,
 //   "attErrorCode": 3,
 //   "iosErrorCode": null,
 //   "androidErrorCode": null,
 //   "reason": "Writing is not permitted.",
 //   "name": "BleError"
 // }

Edit:

I finally found how to get data from the device!
On my case, I need to setup a monitor on another characteristics.

1. send data to characteristicA
2. get result from characteristicB

RE: What's the nRF Connect data format when writing chraracteristics ?

Aleksander Nowakowski — Fri, 21 Jun 2024 10:07:53 GMT

Hello,

that "0x" indicates, that following data are shown in hex. You just need to send an array of bytes with values: 0x30, 0x05, 0x51, etc. and you'll get an array as return. Don't send them as string, but as byte array.

A byte value can be displayed in multiple formats, for example:

64 (decimal)
0x41 (hex)
0101 (octal)
0b01000001 (binary)
'A' (character)

Assuming you're using = FAQ: Passing And Retrieving Of Characteristic Value · dotintent/react-native-ble-plx Wiki (github.com) you need to Base64 the byte array.

By using Hex to Base64 | Base64 Encode | Base64 Converter | Base64 and putting the above hex, we get: MAVRdRRennI=

RE: What's the nRF Connect data format when writing chraracteristics ?

Elfving — Wed, 19 Jun 2024 13:24:56 GMT

Hi David,

I'll get back to you on this tomorrow.

Regards,

Elfving