[Python] How to read from Registers with pymodbus

how can I read from Register with pymodbus?

I'm trying this piece of code:

import pymodbus
from pymodbus.pdu import ModbusRequest
from pymodbus.client.sync import ModbusSerialClient as ModbusClient
#initialize a serial RTU client instance
from pymodbus.transaction import ModbusRtuFramer

#count= the number of registers to read
#unit= the slave unit this request is targeting
#address= the starting address to read from

client = ModbusClient(method = 'rtu', port='/dev/extcomm/0/0', stopbits = 1, bytesize = 8, parity = 'N' , baudrate= 38400)

#Connect to the serial modbus server
connection = client.connect()
print(connection)

#Starting add, num of reg to read, slave unit.
coil = client.read_holding_registers(0x01,1,unit=1)# address, count,
slave address
print(coil)

#Closes the underlying socket connection
client.close()


This gave me this error:

Modbus Error: [Input/Output] Modbus Error: [Invalid Message] Incomplete message received, expected at least 2 bytes (0 received)


My slave id is number 1 and the register I want to read is also the number 1, but i don't know why is still doesn't want to work.

Continue reading...