树莓派基础实验19：光敏传感器实验

#!/usr/bin/env python
#------------------------------------------------------
#
#       您可以使用下面语句将此脚本导入另一个脚本：
#           “import PCF8591 as ADC”                
#   
#   ADC.Setup(Address)  # 查询PCF8591的地址：“sudo i2cdetect -y 1”
# i2cdetect  is  a  userspace  program to scan an I2C bus for devices.
# It outputs a table with the list of detected devices on the specified bus.
#   ADC.read(channal)   # Channal范围从0到3 
#   ADC.write(Value)    # Value范围从0到255
#
#------------------------------------------------------
#SMBus (System Management Bus,系统管理总线) 
import smbus   #在程序中导入“smbus”模块
import time

# for RPI version 1, use "bus = smbus.SMBus(1)"
# 0 代表 /dev/i2c-0， 1 代表 /dev/i2c-1 ,具体看使用的树莓派那个I2C来决定
bus = smbus.SMBus(1)         #创建一个smbus实例

#在树莓派上查询PCF8591的地址：“sudo i2cdetect -y 1”
def setup(Addr):
    global address
    address = Addr

def read(chn): #channel
    if chn == 0:
        bus.write_byte(address,0x40)   #发送一个控制字节到设备
    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)         # 从设备读取单个字节，而不指定设备寄存器。
    return bus.read_byte(address)  #返回某通道输入的模拟值A/D转换后的数字值

def write(val):
    temp = val  # 将字符串值移动到temp
    temp = int(temp) # 将字符串改为整数类型
    # print temp to see on terminal else comment out
    bus.write_byte_data(address, 0x40, temp) 
    #写入字节数据，将数字值转化成模拟值从AOUT输出

if __name__ == "__main__":
    setup(0x48) 
 #在树莓派终端上使用命令“sudo i2cdetect -y 1”，查询出PCF8591的地址为0x48
    while True:
        print '电位计   AIN0 = ', read(0)   #电位计模拟信号转化的数字值
        print '光敏电阻 AIN1 = ', read(1)   #光敏电阻模拟信号转化的数字
        print '热敏电阻 AIN2 = ', read(2)   #热敏电阻模拟信号转化的数字值
        tmp = read(0)
        tmp = tmp*(255-125)/255+125 
# 125以下LED不会亮，所以将“0-255”转换为“125-255”，调节亮度时灯不会熄灭
        write(tmp)
        time.sleep(2)

#!/usr/bin/env python
import PCF8591 as ADC
import RPi.GPIO as GPIO
import time

DO = 17
GPIO.setmode(GPIO.BCM)

def setup():
    ADC.setup(0x48)
    GPIO.setup(DO, GPIO.IN)


def loop():
    status = 1
    while True:
        print '#######################'
        print 'Digital output: ',GPIO.input(DO)  #光强输出低电平，光弱输出高电平
        print 'Value: ', ADC.read(0)   #光强值低，光弱值高
        print '#######################'
        time.sleep(0.5)

if __name__ == '__main__':
    try:
        setup()
        loop()
    except KeyboardInterrupt: 
        pass