Drive the 1602 LCD with ESP32

[archerindigo]

The LCDs are to be install to the electric box and the charger box to show the battery level.

Make sure the ESP32 on them can drive the LCD.

[archerindigo]

We got 2 LCDs boards from the lab:

• Ordinary 20 columns x 4 rows HD44780 display
• DFR0009 Keypad shield

The first one is tested working.

The LCD shown in the picture is now working along with the NCD reader. The followings have to be noted:

1. The Arduino library LiquidCrystal doesn't fully compatible with ESP32 NodeMCU. Need to comment out begin(16,1 in LiquidCrystal::init to declare and initialize the LiquidCrystal object in global scope.

Related issue on LiquidCrystal official repository: https://github.com/arduino-libraries/LiquidCrystal/issues/41

2. The ESP32 NodeMCU doesn't have enough pins to supply the backlit. May jump wires between A/K and Vdd/Vss with 220Ohm resistor between A and Vdd.

3. Some GPIO on the ESP32 cannot be used, such as GPIO12.

References:

• LiquidCrystal official documentation
• LiquidCrystal repository
• HD44780 Datasheet
• A tutorial on interfacing HD44780 with minimal wiring
• Official tutorial of DFR Keypad shield

[archerindigo]

TODO:

• [x] Test also with the DFR LCD shield

[archerindigo]

The LCD shield is test working as well. Code in #45