树莓派-霍尔传感器实验（模拟）

#/usr/bin/env python

import RPi.GPIO as GPIO

import PCF8591 as ADC

import time

def setup():

	ADC.setup(0x48)

def Print(x):

	if x == 0:

		print ''

		print '*************'

		print '* No Magnet *'

		print '*************'

		print ''

	if x == 1:

		print ''

		print '****************'

		print '* Magnet North *'

		print '****************'

		print ''

	if x == -1:

		print ''

		print '****************'

		print '* Magnet South *'

		print '****************'

		print ''

def loop():

	status = 0

	while True:

		res = ADC.read(0)

		print 'Current intensity of magnetic field : ', res

		if res - 133 < 5 and res - 133 > -5:

			tmp = 0

		if res < 128:

			tmp = -1

		if res > 138:

			tmp = 1

		if tmp != status:

			Print(tmp)

			status = tmp

		time.sleep(0.2)

if __name__ == '__main__':

	setup()

	loop()

#!/usr/bin/env python

#------------------------------------------------------

#

#		This is a program for PCF8591 Module.

#

#		Warnng! The Analog input MUST NOT be over 3.3V!

#    

#		In this script, we use a poteniometer for analog

#   input, and a LED on AO for analog output.

#

#		you can import this script to another by:

#	import PCF8591 as ADC

#	

#	ADC.Setup(Address)  # Check it by sudo i2cdetect -y -1

#	ADC.read(channal)	# Channal range from 0 to 3

#	ADC.write(Value)	# Value range from 0 to 255		

#

#------------------------------------------------------

import smbus

import time

# for RPI version 1, use "bus = smbus.SMBus(0)"

bus = smbus.SMBus(1)

#check your PCF8591 address by type in 'sudo i2cdetect -y -1' in terminal.

def setup(Addr):

	global address

	address = Addr

def read(chn): #channel

	if chn == 0:

		bus.write_byte(address,0x40)

	if chn == 1:

		bus.write_byte(address,0x41)

	if chn == 2:

		bus.write_byte(address,0x42)

	if chn == 3:

		bus.write_byte(address,0x43)

	bus.read_byte(address) # dummy read to start conversion

	return bus.read_byte(address)

def write(val):

	temp = val # move string value to temp

	temp = int(temp) # change string to integer

	# print temp to see on terminal else comment out

	bus.write_byte_data(address, 0x40, temp)

if __name__ == "__main__":

	setup(0x48)

	while True:

		print 'AIN0 = ', read(0)

		print 'AIN1 = ', read(1)

		tmp = read(0)

		tmp = tmp*(255-125)/255+125 # LED won't light up below 125, so convert '0-255' to '125-255'

		write(tmp)

#		time.sleep(0.3)