Decode 8 bit not possible

[hasenradball]

Dear pymodbus team,

with version 3.6.6 it was possible to decode 8 bit values.
But with version 3.9.2 this is no possible anymore, because the DATATYPE.UINT8 and DATATYPE.INT8 are missing.

Could you provide also these datatypes for backward compatiliby?

I used the following function:

def decode_register_readings(self, readings, datatype, count) -> list:
        """Decode the register readings 
        
        Decode readings depending on datatype given
        -----
        Args:
            readings: dats read from register
            datatype: U16, U32 , etc...
            count: number of datatypes to be converted
        
        Returns:
            data: list of decoded values
        """
        decoder = BinaryPayloadDecoder.fromRegisters(readings.registers, \
            byteorder=Endian.BIG, wordorder=Endian.BIG)
        #print(f'decoder : {decoder}')
        data = []
        if datatype == 'U8':
            data = [decoder.decode_8bit_uint() for i in range(count)]
        elif datatype == 'U16':
            data = [decoder.decode_16bit_uint() for i in range(count)]
        elif datatype == 'U32':
            data = [decoder.decode_32bit_uint() for i in range(count)]
        elif datatype == 'U64':
            data = [decoder.decode_64bit_uint() for i in range(count)]
        elif datatype == 'S8':
            data = [decoder.decode_8bit_int() for i in range(count)]
        elif datatype == 'S16':
            data = [decoder.decode_16bit_int() for i in range(count)]
        elif datatype == 'S32':
            data = [decoder.decode_32bit_int() for i in range(count)]
        elif datatype == 'S64':
            data = [decoder.decode_64bit_int() for i in range(count)]
        return data

[janiversen]

Binary payload have not been changed for ages, so if it worked in 3.6.6 it still works.

It is correct that client.fromRegisters (replacement for payload in 4.0) do not have UINT8 and INT8, which is because all modbus data calls deliver minimum 16bit.

DATATYPE is part of client.fromRegisters and not payload, and have never supported 8bit as far as I remember. Your example do not use DATATYPE but only payload, so I do not understand what your problem ?

[hasenradball]

@janiversen

I got the following warning:

BinaryPayloadDecoder is deprecated and will be removed in v3.9.0 ! Please use "client.convert_from_registers()" or "client.convert_to_registers" See documentation: "https://pymodbus.readthedocs.io/en/latest/source/client.html#pymodbus.client.mixin.ModbusClientMixin.convert_from_registers"

[hasenradball]

There are some devices on the market which use 8 bit values.

[janiversen]

that still have nothing to do with missing entries in DATATYPE.

We will not add INT8 and UINT8 as a modbus device cannot return an 8 bit values, so if you need that you have to decode it in the app.

As I wrote payload will be removed in v4.0 we postponed it from v3.9.0, so you have time.

[janiversen]

How can a modbus device return 8bit, that is really non standard. Modbus devices always return registers which are defined to be 16bit!

[janiversen]

If you receive a register (16bit) from your device via pymodbus, and for any reason want to split it into 2 bytes, then use the builtin python functions, it really is outside the scope of pymodbus.

[janiversen]

Closing as this is not a pymodbus problem.

[hasenradball]

Ok Thank you for the feedback.