sensors.py

#!/usr/bin/python

# Script that reads various I2C sensors.
# CCS811, BH1750, HTU21. (Air quality, light, temp & humidity).

# CCS811. "This part will measure eCO2 (equivalent calculated carbon-dioxide) concentration 
# within a range of 400 to 8192 parts per million (ppm), and TVOC (Total Volatile Organic 
# Compound) concentration within a range of 0 to 1187 parts per billion (ppb)."

# "The BH1750 provides 16-bit  light measurements in lux"

# The script sends this values in this order by MQTT:
# TVOC, CO2, light, temperature, humidity

# Connections, pin numbers on RPI's Gpio
# SCL pin 5 Gpio3
# Gnd pin 9 Gnd
# Vcc pin 1 3V3
# SDA pin 3 Gpio2

import sys
from smbus import SMBus
from time import sleep
from datetime import datetime
from htu21 import HTU21
import time
import json
import paho.mqtt.client as paho

broker="192.168.1.190"
mqtt_sensors_topic="magicmirror/sensors"
mqtt_error_topic = "magicmirror/errors"
mqtt_info_topic = "magicmirror/info"
client= paho.Client("MagicMirrorSensors") 

#CCS811
SLAVE_ADDR = 0x5B # Can be 0x5A
# Slave registers to read and write
DEVICE_REG_STATUS = 0x00
DEVICE_REG_MEAS_MODE = 0x01
DEVICE_REG_ALG_RESULT_DATA = 0x02
DEVICE_REG_ERROR_ID = 0xE0
DEVICE_REG_APP_START = 0xF4
# Slave register read values
DEVICE_STATE_BOOT = 0x10
DEVICE_STATE_APP = 0x90
DEVICE_STATE_APP_WITH_DATA = 0x98
# Slave register write values
DEVICE_SET_MODE_10S = [0x10]
DEVICE_SET_SW_RESET = [0x11, 0xE5, 0x72, 0x8A]

# BH1750
BH1750_DEVICE     = 0x23 # Default device I2C address
DEVICE     = 0x23 # Default device I2C address
POWER_DOWN = 0x00 # No active state
POWER_ON   = 0x01 # Power on
RESET      = 0x07 # Reset data register value
# Start measurement at 4lx resolution. Time typically 16ms.
CONTINUOUS_LOW_RES_MODE = 0x13
# Start measurement at 1lx resolution. Time typically 120ms
CONTINUOUS_HIGH_RES_MODE_1 = 0x10
# Start measurement at 0.5lx resolution. Time typically 120ms
CONTINUOUS_HIGH_RES_MODE_2 = 0x11
# Start measurement at 1lx resolution. Time typically 120ms
# Device is automatically set to Power Down after measurement.
ONE_TIME_HIGH_RES_MODE_1 = 0x20
# Start measurement at 0.5lx resolution. Time typically 120ms
# Device is automatically set to Power Down after measurement.
ONE_TIME_HIGH_RES_MODE_2 = 0x21
# Start measurement at 1lx resolution. Time typically 120ms
# Device is automatically set to Power Down after measurement.
ONE_TIME_LOW_RES_MODE = 0x23

# 0 = /dev/i2c-0 (port I2C0), 1 = /dev/i2c-1 (port I2C1)
try:
  i2c_bus = SMBus(1)
except:
  errorRoutine("I2C")

# CCS811
def read_i2c_bus_dev(dev_reg, read_len):
    return i2c_bus.read_i2c_block_data(SLAVE_ADDR, dev_reg, read_len)
def write_i2c_bus_dev(dev_reg, write_data):
    i2c_bus.write_i2c_block_data(SLAVE_ADDR, dev_reg, write_data)

def readCCS811():
  try:
    if read_i2c_bus_dev(DEVICE_REG_STATUS, 1)[0] == DEVICE_STATE_BOOT:
        write_i2c_bus_dev(DEVICE_REG_APP_START, []) # empty write
        write_i2c_bus_dev(DEVICE_REG_MEAS_MODE, DEVICE_SET_MODE_10S)

    read_i2c_bus_dev(DEVICE_REG_ERROR_ID, 1) # clear any errors

    timeout_in_seconds = 30

    while (timeout_in_seconds and
           (read_i2c_bus_dev(DEVICE_REG_STATUS, 1)[0] !=
            DEVICE_STATE_APP_WITH_DATA)):
              sleep(5)
              timeout_in_seconds -= 5

    if not timeout_in_seconds:
        raise

    read_data = read_i2c_bus_dev(DEVICE_REG_ALG_RESULT_DATA, 8)

    eCO2_reading = (read_data[0] << 8) | read_data[1]
    eTVOC_reading = (read_data[2] << 8) | read_data[3]

    #print ("eCO2: ") 
    #print (eCO2_reading)
    #print ("eTVOC: ") 
    #print (eTVOC_reading)
    
    list = []
    list.append(eTVOC_reading)
    list.append(eCO2_reading)
    return list

    #raise ValueError # Used to test the exception

  except Exception as e:
    errorRoutine("CCS811 reading")

# BH1750
def readLight(addr=BH1750_DEVICE):
  # Read data from I2C interface
  try: 
    data = i2c_bus.read_i2c_block_data(addr,ONE_TIME_HIGH_RES_MODE_1)
    return convertToNumber(data)
  except:
    errorRoutine("readLight")

def convertToNumber(data):
  # Simple function to convert 2 bytes of data
  # into a decimal number. Optional parameter 'decimals'
  # will round to specified number of decimal places.
  result=(data[1] + (256 * data[0])) / 1.2
  return (result)

def errorRoutine(src):
  err = str(sys.exc_info()[0])
  err = "Error: " + src + " " + err
  print(err)
  client.publish(mqtt_error_topic, err)

def main():
  print("Main")
  htu = HTU21()

  print("connecting to broker ",broker)
  client.connect(broker)
  client.loop_start() 
  client.publish(mqtt_info_topic,"start")

  jsonValues = ['123']
      
  while True:
    now = datetime.now()
    current_time = now.strftime("%H:%M:%S")
    #print("Current Time =", current_time)

    lightLevel=readLight()
    #print("Light Level : " + format(lightLevel,'.2f') + " lx")
    #print("Temperature: " + format(htu.read_temperature(),'.2f'))
    #print("Humidity: : " + format(htu.read_humidity(),'.2f'))

    lFormat = format(lightLevel,'.2f') 
    tFormat = format(htu.read_temperature(),'.2f')
    hFormat = format(htu.read_humidity(),'.2f')

    try:
        jsonValues = readCCS811()
        jsonValues.append(lFormat)
        jsonValues.append(tFormat)
        jsonValues.append(hFormat)
        #raise ValueError
    except:
        errorRoutine("Json append")

    try: 
        json_decoded_data = json.dumps({"Time": current_time, "TVOC": jsonValues[0], "CO2": jsonValues[1], "light": lFormat, "Temperature": tFormat, "Humidity": hFormat})
        print (json_decoded_data)
        client.publish(mqtt_sensors_topic,json_decoded_data)
    except:
        errorRoutine("Mqtt publish")
    time.sleep(30)

if __name__ == "__main__":
    try:  
        main()
    except KeyboardInterrupt:
        print ('Interrupted')
        client.publish(mqtt_info_topic, "Shutting down")
        client.disconnect() #disconnect
        client.loop_stop() #stop loop
        sys.exit(0)