The PFC8574 and the PFC8574A are I2C port expanders that can be uses to connect a parallel LCD to the I2C pins of the Arduino (or other microcontroller)
PCF8574: 0100A2A1A

PCF8574A: 0111A2A1A0 0111000 =0x38; 0111111= 0x3F
Library that can be used is the newLCD library by Malpartida: https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads
Can define two lcd’s
LiquidCrystal_I2C lcd1(0x20,16,2); // set the first LCD address to 0x20 LiquidCrystal_I2C lcd2(0x21,16,2); // set the second LCD address to 0x21
Initialize them in the setup-section:
lcd1.init(); // initialize the 1st lcd lcd2.init(); // initialize the 2nd lcd
And send text:
lcd1.print("1st Hello!"); lcd2.print("2nd Hello!");
That’s all.
NOTE
Though it is always fun to build something yourself. In this case it might not be worth it: consider this ready built board from DealExtreme.com. for only 1.80 euro you will have the complete board, inclusing headers that will solder right into most LCD’s. The PCF8574P as chip alone, will cost you an average of 2.10 euro
One thought on “I2C interface for LCD”