My son wanted a Rubiks Cube timer, and I told him we could make a really basic one in an hour. So I pulled out the ESP32 with the built in OLED and got a couple buttons to make one. Here is the parts list:

• ESP32
• Buttons
• PCB Board optional

Wiring Diagram

The wiring is easy. It’s just 2 buttons, in series, that connect from pin 16 to ground. Essentially, both buttons need to be pressed to close the circuit.

The code

And then here’s the code. That’s it. Probably the easiest ESP project I’ve done. I used the code from here and modified it so that the timer doesn’t start until you release the button.

#include <Arduino.h>
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Fonts/FreeSans9pt7b.h>
#include <Fonts/FreeSans18pt7b.h>
#include <Fonts/FreeSans12pt7b.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define LOGO_HEIGHT 16
#define LOGO_WIDTH 16

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
const unsigned char PROGMEM icon[] = {
    0x00, 0x1F, 0xF8, 0x00, 0x00, 0x1F, 0xF8, 0x00, 0x00, 0x1F, 0xF8, 0x00, 0x00, 0x1F, 0xF8, 0x00,
    0x00, 0x1F, 0xF8, 0x00, 0x00, 0x03, 0xC0, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0xE0,
    0x00, 0x1F, 0xF8, 0xF0, 0x00, 0x7F, 0xFE, 0x70, 0x00, 0xFF, 0xFF, 0x20, 0x01, 0xF0, 0x0F, 0x80,
    0x03, 0xC1, 0x83, 0xC0, 0x03, 0x81, 0x81, 0xC0, 0x07, 0x01, 0x80, 0xE0, 0x07, 0x01, 0x80, 0xE0,
    0x0E, 0x01, 0x80, 0x70, 0x0E, 0x01, 0x80, 0x70, 0x0E, 0x03, 0xC0, 0x70, 0x0E, 0x03, 0xC0, 0x70,
    0x0E, 0x03, 0xC0, 0x70, 0x0E, 0x01, 0x80, 0x70, 0x0E, 0x00, 0x00, 0x70, 0x07, 0x00, 0x00, 0xE0,
    0x07, 0x00, 0x00, 0xE0, 0x07, 0x80, 0x01, 0xE0, 0x03, 0xC0, 0x03, 0xC0, 0x01, 0xE0, 0x07, 0x80,
    0x00, 0xF8, 0x1F, 0x00, 0x00, 0x7F, 0xFE, 0x00, 0x00, 0x1F, 0xF8, 0x00, 0x00, 0x07, 0xE0, 0x00

};

const unsigned char PROGMEM swatch[] = {
    0x03, 0xC0, 0x03, 0xC0, 0x03, 0xC0, 0x00, 0x08, 0x07, 0xEC, 0x0E, 0x70, 0x18, 0x18, 0x30, 0x0C,
    0x30, 0x8C, 0x21, 0x84, 0x21, 0x84, 0x30, 0x0C, 0x10, 0x08, 0x18, 0x18, 0x0F, 0xF0, 0x03, 0xC0};

void setup()
{
  pinMode(16, INPUT_PULLUP); // Switch

  Wire.begin(5, 4);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C, false, false))
  {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;)
      ;
  }

  /* #region initialize display */
  display.display();
  display.clearDisplay();
  display.setFont(&FreeSans9pt7b);
  display.drawPixel(10, 10, SSD1306_WHITE);
  display.setTextColor(WHITE);
  display.setCursor(0, 0);
  display.print("The Neev Timer");
  display.display();
  delay(800);
  /* #endregion */
}

/* #region Initialize global vars */
int sec1 = 0;
int min1 = 0;
unsigned long msec = 0;
unsigned long mili = 0;
int pres = 0;
int fase = 0;
int start = 0;
unsigned long tim = 0;
/* #endregion */

void loop()
{
  display.clearDisplay();
  if (digitalRead(16) == 0)
  {
    if (pres == 0)
    {
      fase = fase + 1;
      pres = 1;
      if (fase > 2)
        fase = 0;
    }
  }
  else
  {
    pres = 0;
  }

  if (fase == 0)
  {
    display.setFont(&FreeSans12pt7b);
    display.setFont();
    display.setCursor(50, 50);
    display.print("Start");
    display.drawBitmap(48, 8, icon, 32, 32, WHITE);

    sec1 = 0;
    min1 = 0;
    tim = 0;
    mili = 0;
    msec = 0;
    start = 0;
  }

  if (fase == 1)
  {

    display.clearDisplay();
    display.setFont(&FreeSans12pt7b);
    display.setFont();
    display.setCursor(37, 0);
    display.print("Stopwatch");
    display.setFont(&FreeSans9pt7b);
    if (digitalRead(16) == 0)
    {
      tim = 0;
    }
    else if (start == 0)
    {
      start = 1;
      tim = millis();
      msec = (millis() - tim);
    }
    else msec = (millis() - tim);

    min1 = msec / 60000;

    if ((msec / 1000) > 59)
    {
      sec1 = (msec / 1000) - (min1 * 60);
    }
    else
    {
      sec1 = msec / 1000;
    }

    mili = (msec % 1000) / 10;

    display.setCursor(42, 30);
    if (min1 <= 9)
    {
      display.print("0");
      display.print(min1);
    }
    else
    {
      display.print(min1);
    }

    display.print(":");

    if (sec1 <= 9)
    {
      display.print("0");
      display.print(sec1);
    }
    else
    {
      display.print(sec1);
    }
    display.setFont(&FreeSans12pt7b);
    display.setCursor(50, 57);

    if (mili <= 9)
    {
      display.print("0");
      display.print(mili);
    }
    else
    {
      display.print(mili);
    }
  }

  if (fase == 2)
  {
    display.clearDisplay();
    display.setFont(&FreeSans12pt7b);
    display.setFont();
    display.setCursor(52, 0);
    display.print("Time:");
    display.setFont(&FreeSans9pt7b);
    display.setCursor(42, 30);
    if (min1 <= 9)
    {
      display.print("0");
      display.print(min1);
    }
    else
    {
      display.print(min1);
    }

    display.print(":");

    if (sec1 <= 9)
    {
      display.print("0");
      display.print(sec1);
    }
    else
    {
      display.print(sec1);
    }
    display.setFont(&FreeSans12pt7b);
    display.setCursor(50, 57);

    if (mili <= 9)
    {
      display.print("0");
      display.print(mili);
    }
    else
    {
      display.print(mili);
    }
    display.drawBitmap(105, 20, swatch, 16, 16, 1);
    display.drawBitmap(12, 20, swatch, 16, 16, 1);
  }

  display.display();
}