Pymodbus将浮点数添加到服务器上下文寄存器

Question

I'm new to pymodbus and modbus in general, I've been trying for some time now to add a float directly
to server context without any success, I wondered if you had any lead on how to do it. I already try to use payload by doing something like :

builder = BinaryPayloadBuilder(endian=Endian.Little)
builder.add_32bit_float(long(69000))
payload = builder.build()

context[slave_id].setValues(register, address, payload)

However I get an error about pymodbus trying to cast the payload to int, my code is mostly the one from the sync server example. Any help would be very nice

Answer 1

builder = BinaryPayloadBuilder(endian=Endian.Little)
builder.add_32bit_float(30.3)
payload = builder.to_registers()

context[slave_id].setValues(register, address, payload)

This is the correct way, take note that "register" is the starting registers and all modbus registers are 16 bit wide so a 32 bit float occupies 2 (register and register+1).

Answer 2

After some research on register and and splitting of float into 16bit integer I came up with :

register = 3
slave_id = 0x00
address  = 0x01

values   = context[slave_id].getValues(register, address, count=2)

# Two integers to a floating point
i1 = values[0]
i2 = values[1]
f = unpack('l',pack('<HH',i1,i2))[0]
f = f+1
# Floating point to two integers
i1, i2 = unpack('<HH',pack('l',f))
print(f,i1,i2)

context[slave_id].setValues(register, address, [i1,i2])

I had some issue with the encoding in Endian check what is the one you need with your modbus client,