caliper sketch

/*
  based on the original work done by
  (c)2018 Pawel A. Hernik
  YouTube video:
  https://youtu.be/RIt08GJH2IA
https://www.instructables.com/Fun-With-OLED-Display-and-Arduino/

*/

/*
   Cheap digital caliper pinout (from top left):
   LOOKING AT THE FACE OF THE DEVICE
   #1 - GND (Brown)              | BLACK IN VIDEO
   #2 - DAT (Blue)               | GREEN IN VIDEO
   #3 - CLK (WH/Blue)            | BLUE IN VIDEO
   #4 - VCC 1.5-1.8V (WH/BRown)  | RED IN VIDEO
 */
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);



#define DATA_PIN  1 // green
#define CLOCK_PIN 2 // white-green

// These are pins A2 & A3
// digitalWrite(pin, value)
// for grabbing power and ground from other pins like A0 and A1

void setup()
{
  Serial.begin(9600);

pinMode(0, OUTPUT);    // sets the digital pin as output
pinMode(3, OUTPUT);    // sets the digital pin as output

digitalWrite(0, LOW); // GROUND white-orange
digitalWrite(3, HIGH);  // +5V orange

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }

  Serial.println("Ready");

  pinMode(CLOCK_PIN, INPUT);
  pinMode(DATA_PIN, INPUT);

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(10, 0);
  // Display static text
  Serial.println("Hello World! Setup");
//  display.println("Hello World! Setup");
//  display.display();
  delay(500);
//  display.clearDisplay();
//  display.setCursor(10, 0);
  Serial.println("Caliper Setup");
//  display.println("Caliper Setup");
//  display.display();
}

char buf[20];
unsigned long tmpTime;
int sign;
int inches;
int cm;
long value;
float result;

void loop()
{
  while(digitalRead(CLOCK_PIN)==LOW) {}
  tmpTime=micros();
  while(digitalRead(CLOCK_PIN)==HIGH) {}
//  while(digitalRead(CLOCK_PIN)==HIGH) { Serial.println("Clock is still high."); }
  if((micros()-tmpTime)<500) return;
  readCaliper();
  Serial.println(result,2); Serial.println(inches);
  buf[0]=' ';
  dtostrf(result,6,3,buf+1); strcat(buf," in ");
//  display.setCursor(20, 0);
//  display.println(buf);
//  Serial.println(result,2); Serial.println(inches);
//  Serial.println("Inch Rreading");
  Serial.println(buf);

  dtostrf(result*2.54,6,3,buf+1); strcat(buf," cm ");
//  display.setCursor(30, 0);
//  display.println(buf);
//  Serial.println(result*2.54, 2); Serial.println(cm);
//  Serial.println("cm Rreading");
  Serial.println(buf);
  delay(250);
//  display.display();
}

void readCaliper()
{
  sign=1;
  value=0;
  inches=0;
  for(int i=0;i<24;i++) {
    while(digitalRead(CLOCK_PIN)==LOW) {}
    while(digitalRead(CLOCK_PIN)==HIGH) {}
    if(digitalRead(DATA_PIN)==HIGH) {
      if(i<20) value|=(1<<i);
      if(i==20) sign=-1;
      if(i==23) inches=1; // doesn't work with my caliper, always returns inches
    }
  }
  result=(value*sign)/(inches?2000.0:100.0);
}