LiquidCrystal_I2C

LiquidCrystal_I2C

This is small and fast Arduino library for LCD HD44780 and its clones (S6A0069, KS0066U, NT3881D, LC7985, ST7066, SPLC780, WH160xB, AIP31066, GDM200xD). The display operates in 4-bit mode over I²C bus with 8-bit I/O expander PCF8574/PCF8574A.

The 99.9% of all PCF8574(A) I²C backpacks available on the market are connected like this:

PCF8574 ports	LCD pins
P0	4/RS
P1	5/RW
P2	6/En
P3	16/BACKLIGHT LED- (turn-on level HIGH/POSITIVE)
P4	11/DB4
P5	12/DB5
P6	13/DB6
P7	14/DB7

The initialization string for this connection:

//                    A2=HIGH, A1=HIGH, A0=HIGH P0 P1 P2 P3  P4  P5  P6  P7  backlight turn-on level
LiquidCrystal_I2C lcd(PCF8574_ADDR_A21_A11_A01, 4, 5, 6, 16, 11, 12, 13, 14, POSITIVE);

But what if your I²C backpack is different? For example, LCD pin 4/RS is connected to port P6 and LCD’s pin 13/DB6 is connected to port P0:

PCF8574 ports	LCD pins
P0	13/DB6 :warning:
P1	5/RW
P2	6/En
P3	16/BACKLIGHT LED- (turn-on level HIGH/POSITIVE)
P4	11/DB4
P5	12/DB5
P6	4/RS :warning:
P7	14/DB7

The initialization string in this case:

//                    A2=HIGH, A1=HIGH, A0=HIGH P0 P1 P2  P3  P4  P5  P6 P7  backlight turn-on level
LiquidCrystal_I2C lcd(PCF8574_ADDR_A21_A11_A01, 13, 5, 6, 16, 11, 12, 4, 14, POSITIVE);

Supports:

• Arduino AVR
• Arduino ESP8266
• Arduino ESP32
• Arduino STM32
• Arduino SAMD21