import minimalmodbus
import sys


SERIAL_PORT = '/'
DEVICE_ADDRESS = 1
DECIMAL_COUNT

def modbus_RTU():
    try:
        device = minimalmodbus.Instrument(SERIAL_PORT, DEVICE_ADDRESS)
        r1_value = device.read_register(1, DECIMAL_COUNT)
        r3_value = device.read_register(3, DECIMAL_COUNT)
        print r1_value
        print r3_value
    except IOError:
        print "communication error with device"
        sys.exit(1)


if __name__ == "__main__":
    modbus_RTU()