import paho.mqtt.client as mqtt
import smbus
import time
import os
import sys

time.sleep(30) #Sleep to allow wireless to connect before starting MQTT

username = "1234567890"
password = "abcdefgghi"
clientid = "12345-abcd"

mqttc = mqtt.Client(client_id=clientid)
mqttc.username_pw_set(username, password=password)
mqttc.connect("mqtt.mydevices.com", port=1883, keepalive=60)
mqttc.loop_start()

topic_si7021_temp = "v1/" + username + "/things/" + clientid + "/data/3"
topic_si7021_humidity = "v1/" + username + "/things/" + clientid + "/data/4"

while True:
	try:  
# Get I2C bus
		bus = smbus.SMBus(1)
		bus.write_byte(0x40, 0xF5)
		time.sleep(0.3)

# SI7021 address, 0x40  Read 2 bytes, Humidity
		data0 = bus.read_byte(0x40)
		data1 = bus.read_byte(0x40)

# Convert the data
		humidity = ((data0 * 256 + data1) * 125 / 65536.0) - 6
 
		time.sleep(0.3)
		bus.write_byte(0x40, 0xF3)
		time.sleep(0.3)
 
# SI7021 address, 0x40 Read data 2 bytes, Temperature
		data0 = bus.read_byte(0x40)
		data1 = bus.read_byte(0x40)
 
# Convert the data and output it
		celsTemp = ((data0 * 256 + data1) * 175.72 / 65536.0) - 46.85
		fahrTemp = celsTemp * 1.8 + 32
    
		if fahrTemp is not None:
			fahrTemp = "temp,f=" + str(fahrTemp)
			mqttc.publish(topic_si7021_temp, payload=fahrTemp, retain=True)
		if humidity is not None:
			humidity = "rel_hum,p=" + str(humidity)
			mqttc.publish(topic_si7021_humidity, payload=humidity, retain=True)
		time.sleep(5)
	except (EOFError, SystemExit, KeyboardInterrupt):
		mqttc.disconnect()
		sys.exit()