Template: PCF8574 IO Expansion Board RPi Guide

Raspberry Pi

Enable I2C Interface

Open a terminal and run the following commands:

sudo raspi-config 
Choose Interfacing Options -> I2C -> Yes.

Reboot Raspberry Pi:

sudo reboot

Install Library

If you use the bookworm system, you can only use lgpio library, bcm2835 and wiringPi can't be installed and used.

BCM2835

#Open the Raspberry Pi terminal and run the following command
wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.71.tar.gz
tar zxvf bcm2835-1.71.tar.gz 
cd bcm2835-1.71/
sudo ./configure && sudo make && sudo make check && sudo make install
# For more, you can refer to the official website at: http://www.airspayce.com/mikem/bcm2835/

WiringPi

#Open the Raspberry Pi terminal and run the following command
cd
sudo apt-get install wiringpi
#For Raspberry Pi systems after May 2019 (earlier than that can be executed without), an upgrade may be required:
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
gpio -v
# Run gpio -v and version 2.52 will appear, if it doesn't it means there was an installation error

# Bullseye branch system using the following command:
git clone https://github.com/WiringPi/WiringPi
cd WiringPi
. /build
gpio -v
# Run gpio -v and version 2.70 will appear, if it doesn't it means there was an installation error

lgpio

#Open the Raspberry Pi terminal and run the following command
wget https://github.com/joan2937/lg/archive/master.zip
unzip master.zip
cd lg-master
sudo make install

# You can refer to the official website for more: https://github.com/gpiozero/lg

Python3

sudo apt-get update
sudo apt-get install python3-pip
sudo apt-get install python3-pil
sudo apt-get install python3-numpy
sudo pip3 install RPi.GPIO
sudo pip3 install spidev

Download examples

Open a terminal of the Raspberry Pi

sudo apt-get install p7zip-full -y
sudo wget  https://files.waveshare.com/upload/1/14/PCF8574-Code.7z
7z x PCF8574-Code.7z -O./PCF8574-Code
cd PCF8574-Code/RaspberryPi/

Hardware connection

PCF8574	Raspberry Pi	Description
	Board order
VCC	5V	Power input
GND	GND	Power ground
SDA	3	I2C data input
SCL	5	I2C clock pin

Run examples

C examples

cd ~/PCF8574-Code/RaspberryPi/
cd wiringPi
sudo make clean
sudo make 
sudo ./test

Python example

cd ~/PCF8574-Code/RaspberryPi/
cd python
sudo python3 PCF8574.py

Expected result

Check the voltage level of every IO, P0 ~ P3 is set to High and the P4 ~ P7 is set to Low.