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I made it work in version 1.20.2.rc7 (dated 2020-05-04) by going into serial.py file and replacing readall function call by read.
Anyhow, isn't a better library? A port of minimalmodbus will be great as I hard to hardcode some things to be able to read inverse float values.
I've filled this issue at github's repo, but last commit is 12 months ago...
Issue content:
Hi,
I'm reading values from a sensor that uses RS485 and sends inverse float values with function code 4 (addresses 0, 2 and 4) and it was imposible for me to read those values using the read_input_registers function (which uses function code 4).
I had to add another function for converting values to float instead of short (quite hardcoded for my case, not so much into modbus):
def _to_float(self, byte_array, signed=True):
# response_quantity = int(len(byte_array) / 2)
# this always returned 2
# fmt = '>' + ('f' * response_quantity)
# so fmt ended up like '>ff' and caused a buffer issue, so I hardcoded it to ' >f'
# also, no idea about signed floats, just left the signed var to be consistent
return struct.unpack('>f', byte_array)
and a new function copy&pasted from read_input_registers, but using the _to_float` function defined above:
def read_float_registers(self, slave_addr, starting_address, register_quantity, signed=True):
modbus_pdu = functions.read_input_registers(starting_address, register_quantity)
resp_data = self._send_receive(modbus_pdu, slave_addr, True)
register_value = self._to_float(resp_data, signed)
return register_value
Any cleaner/correct/good way to implement this?
