Using common LCD controller on MRR ESPE

The LCD connector on the MRR ESPE, which is an ESP32-based 3D printer board, is designed for the Creality CR-10 stock display, but that did not stop me from trying to get it to work with the more common RepRapDiscount Full Graphics Smart Controller (also called LCD12864). An adapter is used to break out the LCD connector pins to the EXP1 and EXP2 format.

Configuration.h needs to be changed:
#define REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER
#define ST7920_DELAY_1 DELAY_NS(500)
#define ST7920_DELAY_2 DELAY_NS(500)
#define ST7920_DELAY_3 DELAY_NS(500)
(I needed the delays to prevent garbled display, but please try without the delays, and only add them if the display is garbled.)

To use the SD card slot on the LCD controller, additional jumper wires are needed to connect the pins on the adapter to the respective pins on the MRR ESPE. The SD_EN jumper also needs to be removed.

Warning/Note: Before using the adapter, CHECK your LCD controller. The problem with Chinese clones is that some of the adapters have the EXP1 and EXP2 connected in reverse. The easiest way to check is to make sure your printer is not powered. Then, connect the cables from the MRR ESPE to the adapter, and from the adapter to the LCD controller. Next, using a multimeter, check for connectivity between the SD card slot on the LCD adapter (which is connected to GND) and the microSD card slot on the MRR ESPE (which is also connected to GND). If there is connectivity, good! It means that everything should work when you power up the system. If there is no connectivity, chances are the LCD controller has the EXP1/EXP2 connectors in reverse.

MRR ESPA and MRR ESPE available here.
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