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Monitor Digital Inputs

Digital Inputs

The eight digital inputs allow software applications running on the Raspberry Pi to monitor the status of external signals. The inputs can be connected to 12V signals (maximum 30V). The PCF8574 I2C device can be polled to monitor the inputs. When an input is greater then 6V, the device will report as "1" or ON and when less than 6V it will report a "0" or OFF.

Python Test Program

import smbus

import time

from os import system

bus=smbus.SMBus(1)

**** Digital Output

PCF8574=0x20


***** Digital Input         

def PCF8574_input():

                val =  bus.read_byte(PCF8574)

                return val


***** Initialize the devices


while True:

                print "Input {0:b} ".format(PCF8574_input())

                time.sleep(1)