read method
Implementation
Future<Uint16List?> read(int slave, RegisterType rtype, int addr, int size,
QualifiedCharacteristic writer,Function listen,
{int retry = 5, int timeout = 500}) async {
Uint8List data;
switch (rtype) {
case RegisterType.holding:
data = ModbusPtl.readHoldingRegister(slave, addr, size);
break;
case RegisterType.input:
data = ModbusPtl.readInputRegister(slave, addr, size);
break;
default:
throw UnsupportedError('Unsupported register type: $rtype');
}
List<int>? ret = await call(data, writer, listen);
if (ret == null) return null;
Tuple3<int, int, Uint16List>? recv = ModbusPtl.r_modbus_read(Uint8List.fromList(ret!));
return recv?.item3;
}