Convert two 16 Bit Registers to 32 Bit float value flutter

Question

I am using a Modbus flutter lib, reading 2 registers I obtain:

[16177, 4660] I need a function to convert it to a 32 bit float value: 0.7

I found this function

ByteBuffer buffer = new Uint16List.fromList(fileBytes).buffer;
ByteData byteData = new ByteData.view(buffer);
double x = byteData.getFloat32(0);

It says 0.000045747037802357227 swap byte value

Can you help

Answer 1

I always find it easiest to start with the byte array and insert stuff into that. What's happening is that your code is defaulting to the native endianness (apparently little) but you need to be doing this in big endianness.

Here's an overly verbose solution that you can cut out the print statements (and hex codec)

import 'dart:typed_data';
import 'package:convert/convert.dart'; // only needed for debugging

void main() {
  final registers = [16177, 4660];
  final bytes = Uint8List(4); // start with the 4 bytes = 32 bits

  var byteData = bytes.buffer.asByteData(); // ByteData lets you choose the endianness
  byteData.setInt16(0, registers[0], Endian.big); // Note big is the default here, but shown for completeness
  byteData.setInt16(2, registers[1], Endian.big);
  print(bytes); // just for debugging - does my byte order look right?
  print(hex.encode(bytes)); // ditto

  final f32 = byteData.getFloat32(0, Endian.big);
  print(f32);
}