#!/usr/bin/env python3
import minimalmodbus
import serial

slave_address = 0x11
instrument = minimalmodbus.Instrument('/dev/ttyUSB0', slave_address, close_port_after_each_call=True)  # port name, slave address (in decimal)

instrument.serial.baudrate = 115200
instrument.serial.bytesize = 8
instrument.serial.parity   = serial.PARITY_EVEN
instrument.serial.stopbits = 1
instrument.serial.timeout  = 0.05          # seconds
instrument.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
instrument.clear_buffers_before_each_transaction = True

# read
CO2 = instrument.read_register(9, 1, functioncode=4) * 10
print(CO2)