#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

#define ADXL345_ADDR 0x53
#define POWER_CTL 0x2D
#define MOTION_VARIATION_THRESHOLD 5

int16_t prevX = 0, prevY = 0, prevZ = 0;

void setup() {
  Serial.begin(115200);
  Wire.begin();
  lcd.init();
  lcd.backlight();
  lcd.print("Init...");
  delay(500);
  lcd.clear();
  Wire.beginTransmission(ADXL345_ADDR);
  Wire.write(POWER_CTL);
  Wire.write(0x08);
  Wire.endTransmission();
  delay(100);
}

void loop() {
  int16_t x, y, z;
  readADXL345(x, y, z);

  bool motionDetected = abs(x - prevX) > MOTION_VARIATION_THRESHOLD ||
                        abs(y - prevY) > MOTION_VARIATION_THRESHOLD ||
                        abs(z - prevZ) > MOTION_VARIATION_THRESHOLD;

  prevX = x; prevY = y; prevZ = z;

  lcd.clear();
  if (!motionDetected) {
    lcd.setCursor(0, 0);
    lcd.print("Apnea Detected");
  } else {
    lcd.setCursor(0, 0);
    lcd.print("No Apnea");
  }
  lcd.setCursor(0, 1);
  lcd.print("X:");
  lcd.print(x);

  Serial.print("X:"); Serial.print(x);
  Serial.print(" Y:"); Serial.print(y);
  Serial.print(" Z:"); Serial.println(z);

  delay(2000);
}

void readADXL345(int16_t &x, int16_t &y, int16_t &z) {
  Wire.beginTransmission(ADXL345_ADDR);
  Wire.write(0x32);
  Wire.endTransmission(false);
  Wire.requestFrom(ADXL345_ADDR, 6, true);
  x = Wire.read() | (Wire.read() << 8);
  y = Wire.read() | (Wire.read() << 8);
  z = Wire.read() | (Wire.read() << 8);
}