ST7920 and u8g2 only using some of a 128x64 display

Question

I am trying to use the u8g2 library and an Arduino Mega to control an LCD display. Adapting HelloWorld from the examples included in the library to use the SPI ports of the Mega (50-52), I have the code below.

This gives a bit of a disappointing greeting as in the picture below. It seems that the Arduino is not accessing all the pixels, and only able to change the states of three blocks (the top one with "Hello V", and the two darker regions at the bottom).

The display is a 128X64ZW-10 salvaged from a 3D printer which was working when connected to the printer's motherboard. Pin-out deduced by some kind folk here and here (translation). I briefly saw random Pinyin characters flash across the whole display while I was switching wires. These two facts, and the fact that the regions of pixels that are working are not arranged at random, makes me suspect it is a wiring or coding issue, and that the pixels are not dead.

Here is the code:

#include <Arduino.h>
#include <U8g2lib.h>

#ifdef U8X8_HAVE_HW_SPI
#include <SPI.h>
#endif
#ifdef U8X8_HAVE_HW_I2C
#include <Wire.h>
#endif

int LCD_CLK_PIN = 52; //Clock (white)
int LCD_RW_PIN = 50; //Read-Write (blue)
int LCD_RS_PIN = 51;  //Register Select (green)
U8G2_ST7920_128X64_F_SW_SPI u8g2(U8G2_R0, LCD_CLK_PIN, LCD_RW_PIN, LCD_RS_PIN,U8X8_PIN_NONE);

void setup(void) {

  /* U8g2 Project: SSD1306 Test Board */
  //pinMode(10, OUTPUT);
  //pinMode(9, OUTPUT);
  //digitalWrite(10, 0);
  //digitalWrite(9, 0);     

  /* U8g2 Project: T6963 Test Board */
  //pinMode(18, OUTPUT);
  //digitalWrite(18, 1);    

  /* U8g2 Project: KS0108 Test Board */
  //pinMode(16, OUTPUT);
  //digitalWrite(16, 0);    

  /* U8g2 Project: LC7981 Test Board, connect RW to GND */
  //pinMode(17, OUTPUT);
  //digitalWrite(17, 0);    

  /* U8g2 Project: Pax Instruments Shield: Enable Backlight */
  //pinMode(6, OUTPUT);
  //digitalWrite(6, 0); 

  u8g2.begin();  
}

void loop(void) {
  u8g2.firstPage();
  do {
    u8g2.setFont(u8g2_font_ncenB10_tr);
    u8g2.drawStr(1,18,"Hello World!");
  } while ( u8g2.nextPage() );
  //delay(1000);
}

I have spent a couple of days on this, but no luck. Any ideas?

Answer 1

Many thanks for your photos.

Test carried out with the motherboard of an Ender3 V1.1.3

PIN configuration: U8g2lib library

#include <U8g2lib.h>

#ifdef U8X8_HAVE_HW_SPI
#include <SPI.h>
#endif
#ifdef U8X8_HAVE_HW_I2C
#include <Wire.h>
#endif

int LCD_CLK_PIN = 30; //Clock (white)
int LCD_RW_PIN = 17; //Read-Write (blue)
int LCD_RS_PIN = 28;  //Register Select (green)
U8G2_ST7920_128X64_F_SW_SPI u8g2(U8G2_R0, LCD_CLK_PIN, LCD_RW_PIN, LCD_RS_PIN,U8X8_PIN_NONE);

configuration PIN: library U8glib

#include "U8glib.h"
U8GLIB_ST7920_128X64_1X u8g(30, 17, 28);  // SPI Com: SCK = en = 18, MOSI = rw = 16, CS = di = 17

Your program is working properly.