How to use convert_from_registers instead with different data types?

[d-el]

How to use convert_from_registers instead of BinaryPayloadDecoder with multiple different data types?
Old code:

result = self.client.read_holding_registers(0x0200, count=21,  slave=1)
decoder = payload.BinaryPayloadDecoder.fromRegisters(result.registers, byteorder=constants.Endian.BIG, wordorder=constants.Endian.LITTLE)
voltage = decoder.decode_32bit_int()
current = decoder.decode_32bit_int()
temperature = decoder.decode_16bit_int()
...

[janiversen]

Please see the examples.

[d-el]

In example used deprecated BinaryPayloadDecoder.

[janiversen]

That is only one example (which is still there because the payload is still there), there are others.

[patfrench]

Hi

I have a device that has a large amount of registers, I can't read and decode each register one by one.
I'm reading 15 registers but inside there are float32, uint32 and uint64 and I'm wondering how to decode?
My intuition tells me:

u16 = client.convert_from_registers(rr.registers[offset:offset+1] ...
offset += 1
# un uint32
u32 = client.convert_from_registers(rr.registers[offset:offset+2] ....
offset += 2
# un float32
f32 = client.convert_from_registers(rr.registers[offset:offset+2] ....

Thank you

[janiversen]

It is not only your intuition but also the documentation.

You need to call from_registers multiple times.

[bambosd]

Hello, i have also some code using the old style with endian big / little etc...
what would be the method to update the code with the new client.convert_from_registers ?
specifically, i had all the 4 different possible types of float , byte endian big and little, word endian big and little.
How to do that with the new function ?

[janiversen]

4 types is impossible with standard modbus ! because the frames being sent/received are pr definition big endian, your cpu is either big or little, leaving only 2 types.

If you look at the signatures of convert to/from it tells you what to do.

[bambosd]

4 types is impossible with standard modbus ! because the frames being sent/received are pr definition big endian, your cpu is either big or little, leaving only 2 types.

If you look at the signatures of convert to/from it tells you what to do.

ok, yes, you have a point. but specifically for float32 , some modbus devices are reversing bytes because of their primary protocol. for example 104 Protocol Gateways. (IEC 60870-5-104). so from the old library we had endianess of bytes and endianess of words, by setting BIG and LITTLE. all cases was 4. I'm not saying that all the types are used, i'm just saying that strange devices can do this unusual encoding. to read this device i used byte swap and word swap at the same time, (DCBA).

also swapped words is used on many devices. maybe is better to keep the functionality somehow.

[janiversen]

Pymodbus support the modbus standard and that is big endian for bytes, and not defined for words....which is why pymodbus offers big/little for words but not for bytes.

Swapping bytes is actually a functionality built into python so no need for Pymodbus to include it.