Convert any standard 16 pin LCDs like 8x1, 8x2, 16x2, 16x4 and 20x4 LCDs with this I2C backpack. Easy to use and occupies just 2 MCU I/O.
Using the LCD backpack, desired data can be displayed on the LCD through the I2C bus. In principle, such backpacks are built around PCF8574 (from NXP) which is a general purpose bidirectional 8 bit I/O port expander that uses the I2C protocol. The PCF8574 is silicon CMOS circuit provides general purpose remote I/O expansion (an 8-bit quasi-bidirectional) for most microcontroller families via the two-line bidirectional bus (I2C-bus). Note that most backpack modules are centered around PCF8574T (SO16 package of PCF8574in DIP16 package) with a default slave address of 0x27. If your backpack holds a PCF8574AT chip, then the default slave address will change to 0x3F. In short, your backpack is based on PCF8574T and the address connections (A0-A1- A2) are not bridged with solder it will have the slave address 0x27.
For this experiment it is necessary to download and install the “Arduino I2C LCD” library. First of all, rename the existing “LiquidCrystal” library folder in your Arduino libraries folder as a backup, and proceed to the rest of the process.
If you are 100% sure that everything is okay, but you don’t see any characters on the display, try to adjust the contrast control pot of the backpack and set it a position where the characters are bright and the background does not have dirty boxes behind the characters.