Bluetooth Flowmeter rev_02

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    - Project: Bluetooth Flowmeter
    - Source Code compiled for: Arduino Nano
    - Source Code created on: 2025-09-09 14:05:33

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/****** SYSTEM REQUIREMENTS *****/
/****** SYSTEM REQUIREMENT 1 *****/
    /* I need to have an Arduino Nano indicate the flow */
    /* value of a YF-S201Y flowmeter that connects to a */
    /* cell phone via Bluetooth to be able to pass the */
    /* flow information in real time */
/****** END SYSTEM REQUIREMENTS *****/




/* START CODE */

/****** DEFINITION OF LIBRARIES *****/
#include <SoftwareSerial.h>

/****** FUNCTION PROTOTYPES *****/
void setup(void);
void loop(void);
void flowISR(void);

/****** GLOBAL CONSTANTS AND VARIABLES *****/
#define FLOW_PIN 2
#define LED_PIN 13
#define PULSE_PER_LITER 450.0

// Bluetooth module connected to pins 10 (RX) and 11 (TX)
SoftwareSerial BTSerial(10, 11); // RX, TX

volatile unsigned long pulseCount = 0;
unsigned long lastPulseCount = 0;
unsigned long lastMillis = 0;
float flowRate = 0.0;
float totalLiters = 0.0;
static unsigned long ledOnTime = 0; // LED on indicator for a short pulse

/****** INTERRUPT SERVICE ROUTINE *******/
void flowISR(void)
{
  pulseCount++;
}

void setup(void)
{
  // put your setup code here, to run once:
  Serial.begin(115200);    // USB serial for debugging
  BTSerial.begin(9600);    // Bluetooth module serial

  pinMode(FLOW_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  // Attach interrupt on rising edge of flow sensor signal
  attachInterrupt(digitalPinToInterrupt(FLOW_PIN), flowISR, RISING);

  lastMillis = millis();
  lastPulseCount = 0;
}

void loop(void)
{
  unsigned long now = millis();
  static unsigned long lastOutputMillis = 0;

  // Update and transmit data once per second
  if ((now - lastOutputMillis) >= 1000)
  {
    unsigned long currentCount;
    unsigned long delta;
    unsigned long dt;

    // Copy pulse count atomically
    noInterrupts();
    currentCount = pulseCount;
    delta = currentCount - lastPulseCount;
    lastPulseCount = currentCount;
    interrupts();

    dt = now - lastOutputMillis;
    if (dt == 0) dt = 1;

    // Calculate flow rate in L/min and total liters
    flowRate = (delta) * (60000.0 / (float)dt) / PULSE_PER_LITER;
    totalLiters = currentCount / PULSE_PER_LITER;

    char msg[64];
    snprintf(msg, sizeof(msg), "FLOW:%.3f L/min; TOTAL:%.3f L\n", flowRate, totalLiters);

    Serial.print(msg);
    BTSerial.print(msg);

    // Visual indicator: brief LED pulse on data update
    if (delta > 0)
    {
      digitalWrite(LED_PIN, HIGH);
      ledOnTime = now;
    }

    if (ledOnTime && (now - ledOnTime) > 40)
    {
      digitalWrite(LED_PIN, LOW);
      ledOnTime = 0;
    }

    lastOutputMillis = now;
  }
}

/* END CODE */