read_rs485_modbus_temp.py

import minimalmodbus
import time
import serial
import datetime
import redis
import pickle

rconn = redis.Redis('localhost')


instrument = minimalmodbus.Instrument('/dev/ttyUSB0', 1, debug=False)  # port name, slave address (in decimal)
instrument.serial.port = '/dev/ttyUSB0'                     # this is the serial port name
instrument.serial.baudrate = 9600         # Baud
instrument.serial.bytesize = 8
instrument.serial.parity   = serial.PARITY_NONE
instrument.serial.stopbits = 1
instrument.serial.timeout  = 0.2        # seconds
instrument.address = 1                         # this is the slave address number
instrument.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
instrument.clear_buffers_before_each_transaction = True

def read_temp():
    return instrument.read_registers(registeraddress=0, number_of_registers=1, functioncode= 3)

def read_humi():
    return instrument.read_registers(registeraddress=11, number_of_registers=1, functioncode= 3)

time.sleep(1)
while True:
    temp = None
    humi = None

    while True:
        try:
            temp = read_temp()
        except:
            print(".", end="")
        if temp != None:
            time.sleep(0.1)
            break
    time.sleep(0.2)
    while True:
        try:
            humi = read_humi()
        except:
            print("*", end="")
        if humi != None:
            time.sleep(0.1)
            break


    t = temp[0]/10.0
    h = humi[0]/10.0
    ts = time.time()
    rconn.set("temphumi", pickle.dumps({"temp":t,"humi":h,"time":ts}))
    print(pickle.loads(rconn.get("temphumi")))
    dt = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    print("\n"+dt+"|"+str(t)+"c, "+ str(h)+"%", end=" ")
    time.sleep(5)