Technical summary
It consists of two parts: a “classic” LCD screen and, on the back, an I2C interface module.
Communication with an Arduino board is done with the I2C protocol (see the internet for more details) over two lines called SCL and SDA. The Vcc and GND power lines must be added.
- SDA –> pin A4 Data (pin 20 on Mega, pin D2 on Wemos D1 mini)
- SCL –> pin A5 Clock (pin 21 on Mega, pin D1 on Wemos D1 mini)
And ‘Pull-Up’ resistors must be placed on each of these lines BUT if there are several modules these resistors must be placed only once (4.7K?). (for the circuit I have, the documentation says that there are 10K? ‘Pull-Up’ resistors, but I could not identify them on the circuit, so I put these 4.7K resistors).
Each module has its own address, which can be fixed or adjustable (the I2C protocol can manage 127 addresses!).
There is an Arduino sketch to scan and find the address of the connected device.
( I2C Scanner.ino Written by Nick Gammon Date: 20th April 2011 for example)
The address can be changed by making ‘straps’ between the interface terminals in the case where there are several I2C modules and they have the same address:
