HeartRateSensor.cpp

#include "HeartRateSensor.h"
#include <Arduino.h>

#define BASELINE_SIZE 16
#define BPM_BUF_SIZE 4
#define SMOOTH_ALPHA 0.4f

#define BEAT_MIN_MS 333
#define BEAT_MAX_MS 1500

void HeartRateSensor::begin() {
    if (!sensor.begin(Wire, I2C_SPEED_FAST)) {
        Serial.println("MAX30102 not found!");
        while (1);
    }

    sensor.setup(
        60,   // LED brightness
        4,    // sample average
        2,    // LED mode (red + IR)
        400,  // sample rate
        411,  // pulse width
        4096  // ADC range
    );

    Serial.println("MAX30102 OK");
}

void HeartRateSensor::update() {
    long irValue = sensor.getIR();
    unsigned long now = millis();

    // 手指偵測
    if (irValue < 50000) {
        finger = false;
        wasAbove = false;

        baselineSum = 0;
        baselineIdx = 0;
        baselineFull = false;

        bpmIdx = 0;
        bpmFilled = 0;
        smooth = 0;
        finalBpm = 0;

        return;
    }
    finger = true;

    // ── 動態基線（移動平均）──
    baselineSum -= baseline[baselineIdx];
    baseline[baselineIdx] = irValue;
    baselineSum += irValue;

    baselineIdx = (baselineIdx + 1) % BASELINE_SIZE;
    if (!baselineFull && baselineIdx == 0) baselineFull = true;

    int n = baselineFull ? BASELINE_SIZE : baselineIdx;
    long irMean = baselineSum / n;

    // 基線未穩定 → 不偵測
    if (!baselineFull && baselineIdx < BASELINE_SIZE / 2) return;

    // ── 過零點偵測（低 → 高）──
    bool isAbove = (irValue > irMean);

    if (isAbove && !wasAbove) {
        if (lastCross > 0) {
            unsigned long interval = now - lastCross;

            if (interval >= BEAT_MIN_MS && interval <= BEAT_MAX_MS) {
                int bpm = (int)(60000.0f / interval + 0.5f);

                bpmBuf[bpmIdx++] = bpm;
                bpmIdx %= BPM_BUF_SIZE;
                if (bpmFilled < BPM_BUF_SIZE) bpmFilled++;

                int sum = 0;
                for (int i = 0; i < bpmFilled; i++) sum += bpmBuf[i];
                int avg = sum / bpmFilled;

                if (smooth == 0) smooth = bpm;
                else smooth = SMOOTH_ALPHA * avg + (1.0f - SMOOTH_ALPHA) * smooth;

                finalBpm = (int)(smooth + 0.5f);

                beatFrame = !beatFrame;

                Serial.print("Interval="); Serial.print(interval);
                Serial.print("ms BPM=");   Serial.print(bpm);
                Serial.print(" Out=");     Serial.println(finalBpm);
            }
        }
        lastCross = now;
    }

    wasAbove = isAbove;
}

int HeartRateSensor::getBpm() {
    return finalBpm;
}

bool HeartRateSensor::fingerDetected() {
    return finger;
}