I2C soil moisture sensor with RaspberryPi

chirp.py

#!/usr/bin/python
# cannot use python3 because smbus not working there
# Modified script from https://github.com/JasperWallace/chirp-graphite/blob/master/chirp.py
# by DanielTamm

import smbus, time, sys

class Chirp:
	def __init__(self, bus=1, address=0x20):
		self.bus_num = bus
		self.bus = smbus.SMBus(bus)
		self.address = address
    
	def get_reg(self, reg):
		# read 2 bytes from register
		val = self.bus.read_word_data(self.address, reg)
		# return swapped bytes (they come in wrong order)
		return (val >> 8) + ((val & 0xFF) << 8)

	def reset(self):
		# To reset the sensor, write 6 to the device I2C address
		self.bus.write_byte(self.address, 6)

	def set_addr(self, new_addr):
		# To change the I2C address of the sensor, write a new address
		# (one byte [1..127]) to register 1; the new address will take effect after reset
		self.bus.write_byte_data(self.address, 1, new_addr)
		self.reset()
		self.address = new_addr

	def moist(self):
		# To read soil moisture, read 2 bytes from register 0
		return self.get_reg(0)

	def temp(self):
		# To read temperature, read 2 bytes from register 5
		return self.get_reg(5)

	def light(self):
		# To read light level, start measurement by writing 3 to the
		# device I2C address, wait for 3 seconds, read 2 bytes from register 4
		self.bus.write_byte(self.address, 3)
		time.sleep(1.5)
		return self.get_reg(4)

	def __repr__(self):
		return "<Chirp sensor on bus %d, addr %d>" % (self.bus_num, self.address)

if __name__ == "__main__":
	addr = 0x20
	if len(sys.argv) == 2:
		if sys.argv[1].startswith("0x"):
			addr = int(sys.argv[1], 16)
		else:
			addr = int(sys.argv[1])
	chirp = Chirp(1, addr)

	print chirp
	print "Moisture\tTemperature\tBrightness"
	while True:
		print "%d\t%d\t%d" % (chirp.moist(), chirp.temp(), chirp.light())
		time.sleep(1)