Arduino PF575 I²C I/O port expander blink example

I got some TI PCF8575 I²C I/O expander devices some years ago and never gave them a try. Yesterday I did... In the title they are named PF575, this is because this is what is printed on the device.

I wrote code for making a LED blink using the I/O expander as simple as possible.

Here you see my setup on a breadboard. On the left is the LED connected via a PNP transistor for voltage control.

I only had 24-SSOP packages so I needed to solder the PCF8575 to a DIP adapter for making it breadboard friendly.

My code:

#include <Wire.h>  /**  *  Arduino PF575/PCF8575 I2C I/O port exapander LED blink example  *  *  Setup:  *  *  1. Connect A0, A1 and A2 to GND to set the address to 0x20.  *  2. Connect SDL and SCL to the Arduino's I2C bus.  *  3. Connect a LED to the P0 port of the I2C exapander.  *     In my setup I am using a PNP Transistor connected to 5V using  *     a resistor, the LED and the Arduino to make sure the LED gets  *     a current from Vcc and not from the I2C exapander port.  *  *  This code is trying to explain how it works as simple as possible.  *  More detailed examples are found on the web. Search for pcf8575 and  *  you will find what you want. */  // Set I2C address int address = 0x20;  void setup(){   Wire.begin();   // Set all ports as output   pf575_write(word(B11111111,B11111111)); }  void loop(){   // Set port P0 on   pf575_write(word(B00000000,B00000001));   delay(1000);   // Set port P0 off   pf575_write(word(B00000000,B00000000));   delay(1000); }  // Function for writing two Bytes to the I2C expander device void pf575_write(uint16_t data) {   Wire.beginTransmission(address);   Wire.write(lowByte(data));   Wire.write(highByte(data));   Wire.endTransmission(); }

Some links:

Permalink: https://hanez.org/2015/09/23/arduino-pf575-i2c-io-port-expander-blink-example/

Arduino PF575 I²C I/O port expander blink example

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