PCF8574.py

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# Filename    : PCF8574.py
# Description : PCF8574 as Raspberry GPIO
# Author      : freenove
# modification: 2018/08/03
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import smbus
import time
class PCF8574_I2C(object):
    OUPUT = 0
    INPUT = 1
    
    def __init__(self,address):
        # Note you need to change the bus number to 0 if running on a revision 1 Raspberry Pi.
        self.bus = smbus.SMBus(1)
        self.address = address
        self.currentValue = 0
        self.writeByte(0)   #I2C test.
        
    def readByte(self):#Read PCF8574 all port of the data
        #value = self.bus.read_byte(self.address)
        return self.currentValue#value
        
    def writeByte(self,value):#Write data to PCF8574 port
        self.currentValue = value
        self.bus.write_byte(self.address,value)

    def digitalRead(self,pin):#Read PCF8574 one port of the data
        value = readByte()  
        return (value&(1<<pin)==(1<<pin)) and 1 or 0
        
    def digitalWrite(self,pin,newvalue):#Write data to PCF8574 one port
        value = self.currentValue #bus.read_byte(address)
        if(newvalue == 1):
            value |= (1<<pin)
        elif (newvalue == 0):
            value &= ~(1<<pin)
        self.writeByte(value)   

def loop():
    mcp = PCF8574_I2C(0x27)
    while True:
        #mcp.writeByte(0xff)
        mcp.digitalWrite(3,1)
        print ('Is 0xff? %x'%(mcp.readByte()))
        time.sleep(1)
        mcp.writeByte(0x00)
        #mcp.digitalWrite(7,1)
        print ('Is 0x00? %x'%(mcp.readByte()))
        time.sleep(1)
        
class PCF8574_GPIO(object):#Standardization function interface
    OUT = 0
    IN = 1
    BCM = 0
    BOARD = 0
    def __init__(self,address):
        self.chip = PCF8574_I2C(address)
        self.address = address
    def setmode(self,mode):#PCF8574 port belongs to two-way IO, do not need to set the input and output model
        pass
    def setup(self,pin,mode):
        pass
    def input(self,pin):#Read PCF8574 one port of the data
        return self.chip.digitalRead(pin)
    def output(self,pin,value):#Write data to PCF8574 one port
        self.chip.digitalWrite(pin,value)
        
def destroy():
    bus.close()
    
if __name__ == '__main__':
    print ('Program is starting ... ')
    try:
        loop()
    except KeyboardInterrupt:
        destroy()