/*
  Dual FS300A Flow Meter on Arduino MEGA (ONLY pins 2 and 3)
  Sensor: FS300A G3/4
  Range : 1–60 L/min
  Pulse : ~508 pulses per liter (verify your unit; clones may vary)

  What this does:
  - Uses ONLY external interrupt pins D2 and D3 on Arduino Mega.
  - Counts sensor pulses for 1 second windows, then computes:
      * frequency (Hz)
      * flow rate (L/min)
      * totalized volume (L)
  - Works best with RISING edge counting. CHANGE (both edges) is supported via a switch.

  Wiring (open-collector Hall output):
  - FS300A Vcc → 5V
  - FS300A GND → GND
  - FS300A signal #1 → D2
  - FS300A signal #2 → D3
  - We use INPUT_PULLUP so the pin idles HIGH and pulses LOW.
*/

// ---------------- Configuration ----------------

// Datasheet nominal pulses per liter; calibrate if your unit differs.
#define FS300A_PULSES_PER_LITER 508.0f

// Hz → L/min conversion: flow(L/min) = Hz × (60 / PulsesPerLiter)
const float PULSE_TO_LPM = 60.0f / FS300A_PULSES_PER_LITER;

// Edge selection:
// - Leave undefined to count only RISING edges (recommended).
// - Define COUNT_BOTH_EDGES to use CHANGE (both edges); code will divide by 2.
// #define COUNT_BOTH_EDGES

// Pins (MEGA external interrupts): ONLY 2 and 3
const uint8_t FLOW1_PIN = 2;   // Sensor channel 1 → D2
const uint8_t FLOW2_PIN = 3;   // Sensor channel 2 → D3

// -------------- State (ISR + main) --------------

// Updated in ISRs; must be volatile. 32-bit for headroom.
volatile uint32_t pulse1 = 0;  // Pulses collected in the current 1 s window (ch1)
volatile uint32_t pulse2 = 0;  // Pulses collected in the current 1 s window (ch2)

// Running totals in liters (floating point).
float totalLiters1 = 0.0f;
float totalLiters2 = 0.0f;

// Timing marker (ms) for 1-second interval
unsigned long tPrev = 0;

// -------------- ISRs --------------
// Keep ISRs short (increment only).
void ISR_Flow1() { pulse1++; }
void ISR_Flow2() { pulse2++; }

// -------------- Setup --------------
void setup() {
  Serial.begin(115200);
  while (!Serial) { /* wait if native USB; on MEGA this passes immediately */ }

  // Open-collector friendly: enable internal pull-ups (idle HIGH, pulse LOW)
  pinMode(FLOW1_PIN, INPUT_PULLUP);
  pinMode(FLOW2_PIN, INPUT_PULLUP);

#ifdef COUNT_BOTH_EDGES
  // Count both edges; we will divide by 2 later
  attachInterrupt(digitalPinToInterrupt(FLOW1_PIN), ISR_Flow1, CHANGE);
  attachInterrupt(digitalPinToInterrupt(FLOW2_PIN), ISR_Flow2, CHANGE);
#else
  // Count a single, clean edge per pulse (recommended)
  attachInterrupt(digitalPinToInterrupt(FLOW1_PIN), ISR_Flow1, RISING);
  attachInterrupt(digitalPinToInterrupt(FLOW2_PIN), ISR_Flow2, RISING);
#endif

  tPrev = millis();

  Serial.println(F("FS300A dual-channel flow monitor (MEGA, pins D2 & D3)"));
  Serial.println(F("Output: CHx: freq=Hz, flow=L/min, total=L"));
}

// -------------- Main Loop --------------
void loop() {
  const unsigned long now = millis();

  // Execute once per second
  if (now - tPrev >= 1000UL) {
    tPrev += 1000UL;  // reduces long-term drift

    // --- Atomically snapshot and reset counters ---
    noInterrupts();
    uint32_t c1 = pulse1; pulse1 = 0;
    uint32_t c2 = pulse2; pulse2 = 0;
    interrupts();

    // --- Convert counts to frequency (Hz) ---
#ifdef COUNT_BOTH_EDGES
    // CHANGE counts both edges ⇒ divide by 2
    float freq1 = c1 * 0.5f;
    float freq2 = c2 * 0.5f;
#else
    float freq1 = (float)c1;
    float freq2 = (float)c2;
#endif

    // --- Convert frequency to flow (L/min) ---
    float flow1 = freq1 * PULSE_TO_LPM;
    float flow2 = freq2 * PULSE_TO_LPM;

    // --- Integrate total volume (L) ---
#ifdef COUNT_BOTH_EDGES
    // Also halve the counts for volume if using CHANGE
    totalLiters1 += (float)c1 * 0.5f / FS300A_PULSES_PER_LITER;
    totalLiters2 += (float)c2 * 0.5f / FS300A_PULSES_PER_LITER;
#else
    totalLiters1 += (float)c1 / FS300A_PULSES_PER_LITER;
    totalLiters2 += (float)c2 / FS300A_PULSES_PER_LITER;
#endif

    // --- Print results ---
    Serial.print(F("CH1: freq="));  Serial.print(freq1, 2);
    Serial.print(F(" Hz, flow="));  Serial.print(flow1, 3);
    Serial.print(F(" L/min, total=")); Serial.print(totalLiters1, 4);
    Serial.println(F(" L"));

    Serial.print(F("CH2: freq="));  Serial.print(freq2, 2);
    Serial.print(F(" Hz, flow="));  Serial.print(flow2, 3);
    Serial.print(F(" L/min, total=")); Serial.print(totalLiters2, 4);
    Serial.println(F(" L"));
  }
}