#include <LiquidCrystal.h>
#include "HX711.h"
#include <math.h>  // Needed for exp()

// HX711 pins
#define DT A0
#define SCK A1

// LCD: RS, E, D4, D5, D6, D7
LiquidCrystal lcd(PB0, PB1, PB10, PB11, PB12, PB13);

// Pins for input/output
const int tareButtonPin = PA2;
const int ledPin = PA3;

// HX711 object
HX711 scale;

// Calibration factor
float calibration_factor = 0.3779;

// Offset for drift correction
float offset_correction = 0;

// Exponential scaling parameters
float max_display_weight = 5000.0; // grams (max expected)
float exp_factor = 0.0008;         // curve steepness

void setup() {
  Serial.begin(9600);
  pinMode(tareButtonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);

  lcd.begin(16, 2);
  lcd.print("Weighing Scale");
  delay(1500);
  lcd.clear();

  // HX711 init
  scale.begin(DT, SCK);
  scale.set_scale(calibration_factor);
  scale.tare();

  // Capture baseline offset
  offset_correction = scale.get_units(10);

  lcd.setCursor(0, 0);
  lcd.print("Taring...");
  delay(1500);
  lcd.clear();

  Serial.println("Scale ready.");
}

float getWeight() {
  float raw = scale.get_units(5);  // Average of 5 readings
  raw -= offset_correction;        // Apply offset

  // Dead zone for noise
  if (raw < 0.5 && raw > -0.5) raw = 0;

  // Exponential scaling (compress large weights, boost small ones)
  if (raw > 0) {
    raw = max_display_weight * (1.0 - exp(-exp_factor * raw));
  }

  return raw;
}

void loop() {
  // Tare button
  if (digitalRead(tareButtonPin) == LOW) {
    lcd.setCursor(0, 0);
    lcd.print("Taring...      ");
    scale.tare();
    offset_correction = scale.get_units(10);
    delay(1500);
    lcd.clear();
  }

  float weight = getWeight();

  // LCD Display
  lcd.setCursor(0, 0);
  lcd.print("Weight:       ");
  lcd.setCursor(8, 0);
  lcd.print(weight, 1);
  lcd.print(" g");

  // LED indicator
  if (weight <= 0.5) {
    digitalWrite(ledPin, LOW);
  } else {
    digitalWrite(ledPin, HIGH);
  }

  // Debug serial
  Serial.print("Weight: ");
  Serial.print(weight, 2);
  Serial.println(" g");

  delay(500);
}