Arduino control board IO port is only 20, plus some sensor, SD card Han, relay modules and more, IO port is not enough, 
the original 1602 screen requires seven IO ports can drive up, we have developed this module can help you save five IO ports, we send arduino library

Product parameters: 
1. supply voltage: +5 V 
2. supports the I2C protocol 
3. with backlight and contrast adjustment potentiometer 
4. 4 line out easier.