/*
  Timing test for ILI9341 LCD

  Forum: https://forum.arduino.cc/t/countdown-timer-with-milliseconds/1156553
  Wokwi: https://wokwi.com/projects/372574871197135873


*/

#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"

#define TFT_DC 9
#define TFT_CS 10
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC);

// Choose the number of digits to print
constexpr byte digits =  12;

constexpr byte Top    = 120;
constexpr byte Left   =   0;
constexpr byte Width  = 12 * digits;
constexpr byte Height = 16;

// set to true for erasing with fillRect 
// set to false for erasing by printing with black
constexpr bool fillRect = false;

unsigned long startTime;
unsigned long number = 0;
char buf[20] {};
char fmt[20];

void setup() {
  Serial.begin(115200);
  tft.begin();
  tft.setTextColor(ILI9341_GREEN);
  tft.setTextSize(2);
  startTime = millis();
  sprintf(fmt, "%%%dd", digits);
}

void printNumber() {
  if (fillRect) {
    tft.fillRect(Left, Top, Width, Height, ILI9341_BLACK);
  } else {
    tft.setCursor(Left, Top);
    tft.setTextColor(ILI9341_BLACK);
    tft.println(buf);
    tft.setTextColor(ILI9341_GREEN);
  }  
  tft.setCursor(Left, Top);
  sprintf(buf, fmt, number);
  tft.println(buf);
  number++;
  if (number % 100 == 0) {
    unsigned long endTime = millis();
    Serial.print("Time per println [msec]:\t");
    Serial.println((endTime - startTime) / 100);
    startTime = millis();
  }
}

void loop() {
  printNumber();
}