/*
 * display_st7920_126x64_u8g2.ino
 *  
 * Test screen update speed with large solid fonts on 
 * a 128x64 LCD screen that uses the ST7920 chip.
 * 
 * Consumes 46% of program storage space and
 * 27% of dynamic memory on a Nano.
 *  
 * Mithat Konar
 */


#include <U8g2lib.h>

/*
   Pin assignments:
   RS [CE/CS/SCE]: 10
   R/W [DIN/DN/MOSI/DATA]: 11 (Arduino HW standard)
   E [CLK/SCLK/SCK]: 13  (Arduino HW standard)
   PSB: ground (enable SPI)
   VCC/VDD: 5V
   GND/VSS: ground
*/

const unsigned int CLOCK_PIN = 13,
                   DATA_PIN = 11,
                   CS_PIN = 10;

U8G2_ST7920_128X64_1_HW_SPI disp = U8G2_ST7920_128X64_1_HW_SPI(U8G2_R0, CS_PIN);

unsigned int counter = 80;
char dispStr[4];    // null terminated char array used to pass to renderer.

void setup(void) {
  disp.begin();
  disp.setColorIndex(1);
}

void loop(void) {
  counter = (counter + 1) % 1000;
    
  // picture loop
  disp.firstPage();
  do {
    disp.setFont(u8g2_font_6x13_tr);
    disp.drawStr(0, 13, "SSD1306 u8g2");

    disp.setFont(u8g2_font_logisoso46_tr);
    String(counter).toCharArray(dispStr, 4);
    disp.drawStr( 0, 63, dispStr);
  } while ( disp.nextPage() );

  /* inherent frame rate is about 9.4 fps with 16 MHz processor 
     (without additional delay). */
  delay(500);
}