How to get desired values from BLE manufacturer data flutter

Question

I am new to flutter and I am working on an app that reads data from a BLE beacon. I have scanned the device and got the manufacturer data as {256:[0,0,0,16,1,57,33,18,0,0,154,10,0,0,94,0]}

the device manufacturer told me to device data like :

KCBAdvDataManufacturerData = <.. .. .. .. .. .. .. .. be 21 01 00 50 08 00 00 5e ..>

The UUID - kCBAdvDataManufacturerData packet contains the sensor data as shown below:

Byte index 8 – 11 = Pressure 32bit value

Byte index 12 – 15 = Temperature 32bit value

Byte index 16 = Battery level in percentage

I am totally not getting any idea that in Dart how can I achieve it from

{256:[0,0,0,16,1,57,33,18,0,0,154,10,0,0,94,0]}

to

Byte index 8 – 11 = Pressure 32bit value

Byte index 12 – 15 = Temperature 32bit value

Byte index 16 = Battery level in percentage

and then in a human-understandable form here temperature is in C pressure in PSI and battery is in %.

Answer 1

There is a list of bytes so you can get sublists from that list with https://api.dart.dev/stable/2.9.1/dart-core/List/sublist.html

That sublist can be converted from 4 bytes into a signed integer for the pressure and temperature values:

Convert 4 byte into a signed integer

I am not sure the index values you have been given look quite right. I am assuming the data is in little endian format so my assumption on the data is:

Pressure = [33,18,0,0] = 4641 (Are you expecting a value of about 46.41psi?)

Temperature = [154,10,0,0] = 2714 (Are you expecting a value of about 27.14c?)

Battery = [94] = 94 (Are you expecting a value of 94%?)

This might be done like the following:

import 'dart:typed_data';

var manufacturerData = Uint8List.fromList([0,0,0,16,1,57,33,18,0,0,154,10,0,0,94,0]);
var pressure = ByteData.sublistView(manufacturerData, 6, 10);
var temperature = ByteData.sublistView(manufacturerData, 10, 14);
var battery = ByteData.sublistView(manufacturerData, 14, 15);
main() {
  print(pressure.getUint32(0, Endian.little));
  print(temperature.getUint32(0, Endian.little));
  print(battery.getUint8(0));
}

Gives me the output:

4641
2714
94