# 簡易的心跳偵測模組零件

利用紅外線發射和接收，偵測血液的流動，透過接收值的變化來計算出心跳的頻率。 這次順便提供matplotlib繪圖package，下次可利用同樣的程式碼畫出類比的動態變化圖。這次並沒有說明matplotlib，如果有興趣可以閱讀我撰寫的電子書第九單元 <http://prg.nctu.me/index.php/2018/09/10/09python/> 或是整本下載 <https://app.gitbook.com/@s761111/s/raspi-sensor/>

{% embed url="<https://youtu.be/jnDkfNji7yc>" %}

```python
# 簡易類比圖形繪製程式
from gpiozero import MCP3008
import time
import matplotlib.pyplot as plt
import matplotlib.animation as animation


hr = MCP3008(0)
period = 0.1

# 圖形起始變數設定
fig, ax = plt.subplots()
line, = ax.plot([], [], lw=2)
ax.grid()
xdata, ydata = [], []


# 心跳資料值迭代產生器
def heart_data(t=0):
    cnt = 0
    while cnt < 1000:
        cnt += 1
        t += 0.1
        time.sleep(period)
        yield t, hr.value * 5


# 圖形啟始函數
def init():
    # gpiozero ADC傳回0與1之間的轉換數值
    ax.set_ylim(0.4, 0.8)
    # 設定Y軸高度，若使用傳回值為10位元的函數，可以改用1023為高度值
    # ax.set_ylim(0, 1023)
    ax.set_xlim(0, 10)
    del xdata[:]
    del ydata[:]
    line.set_data(xdata, ydata)
    return line,


# 心跳圖執行繪製
def run(data):
    # 更新資料
    t, y = data
    xdata.append(t)
    ydata.append(y)
    xmin, xmax = ax.get_xlim()

    if t >= xmax:
        ax.set_xlim(xmin, 2*xmax)
        ax.figure.canvas.draw()
    line.set_data(xdata, ydata)

    return line,


ani = animation.FuncAnimation(fig, run, heart_data, blit=False, interval=10,
                              repeat=False, init_func=init)
plt.show()

# for a, b in data_gen(t=0):
#     print(a, b)
```

```python
# 心跳偵測程式
from gpiozero import MCP3008
import time

period = 0.1
count = 0
hrt_rate = 0
time1, time2 = 0, 0
diff = 0
data1, data2 = 0, 0

ht = MCP3008(0)

while True:
    data1 = ht.value
    time.sleep(period)
    data2 = ht.value
    diff = data2 - data1
    print('diff={}'.format(diff))
    if diff > 0:
        while diff > 0:
            data1 = ht.value
            time.sleep(period)
            data2 = ht.value
            diff = data2 - data1
        count += 1
        if count == 1:
            time1 = time.time()
    else:
        while diff <= 0:
            data1 = ht.value
            time.sleep(period)
            data2 = ht.value
            diff = data2 - data1
        count += 1
        if count == 1:
            time1 = time.time()

    if count > 72:
        time2 = time.time()
        hrt_rate = (count / (time2 - time1)) * 30
        print('心跳頻率約:{}'.format(int(hrt_rate)))
        count = 0
        hrt_rate = 0
        time1, time2 = 0, 0
        time.sleep(5)
```


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