create driver and api for the fheartbeat sensor #1660

haas_lib_bundles/python/libraries/fheartbeat/README.md

+# 手指侦测心跳传感器
+## 一、产品简介
+手指侦测心跳传感器是通过LED和光电晶体管监测手指血压脉冲，来判断人的心脏跳动。其结构简单成本低廉，只能是做一些实验和学习相关的知识（没有医疗实用价值）
+
+<div align="center">
+<img src=./../../docs/images/fheartbeat.png  width=25%/>
+</div>
+
+### 引脚定义
+* -: GND
+* +: 3.3V
+* S: 模拟信号输出
+
+## 二、软件接口
+手指侦测心跳传感器HaaS Python驱动：[下载地址](https://github.com/alibaba/AliOS-Things/tree/master/haas_lib_bundles/python/libraries/fheartbeat)
+<br>
+
+### FHEARTBEAT(adcObj) - 创建FHEARTBEAT驱动对象
+* 函数原型:
+> fheartbeatObj = FHEARTBEAT(adcObj)
+
+* 参数说明:
+
+|参数|类型|必选参数？|说明|
+|-----|----|:---:|----|
+|adcObj|ADC|是|调用此函数前需确保adcObj对象已经处于open状态|
+<br>
+
+* 返回值:
+
+创建对象成功，返回FHEARTBEAT对象；FHEARTBEAT对象创建失败，抛出Exception
+
+* 示例代码:
+
+```python
+from fheartbeat import *
+
+print("Testing fheartbeat  ...")
+adc = ADC()
+adc.open("fheartbeat")
+fheartbeatDev = FHEARTBEAT(adc)
+```
+
+* 输出:
+```log
+Testing fheartbeat  ...
+```
+
+### getVoltage - 测量手指侦测心跳电压值
+
+* 函数功能:
+
+量测手指侦测心跳电压值并返回测量结果
+
+* 函数原型:
+> FHEARTBEAT.getVoltage()
+
+* 参数说明:
+无
+
+* 返回值:
+
+成功返回手指侦测心跳电压值测量结果（数据类型：浮点型；单位：mV）；失败抛出Exception
+
+* 示例:
+
+```python
+from fheartbeat import *
+
+print("Testing fheartbeat  ...")
+adc = ADC()
+adc.open("fheartbeat")
+fheartbeatDev = FHEARTBEAT(adc)
+voltage = fheartbeatDev.getVoltage()
+print("voltage: %d"%voltage)
+```
+
+* 输出:
+```log
+Testing fheartbeat  ...
+voltage: 800.0
+```
+
+## 三、接口案例
+此使用实例在board.json中定义了名为FHEARTBEAT的ADC类型的对象。在Python脚本中周期性的获取手指侦测心跳电压值测量结果并打印在日志中。
+
+* 代码:
+```json
+# board.json配置：
+{
+    "name": "board-name",
+    "version": "1.0.0",
+    "io": {
+        "fheartbeat": {
+        "type": "ADC",
+        "port": 4,
+        "width": 2,
+        "atten": 3,
+        "sampling": 12000000
+      }
+    },
+    "debugLevel": "ERROR",
+    "repl": "disable"
+}
+```
+
+```python
+# Python代码
+import utime                         # 延时API所在组件
+from fheartbeat import *
+
+i = 0
+trip = {}
+print("Testing fheartbeat  ...")
+adc = ADC()
+adc.open("fheartbeat")
+fheartbeatDev = FHEARTBEAT(adc)
+while 1:
+    voltage = fheartbeatDev.getVoltage()
+    trip[i] = voltage
+    i  = i + 1
+    if i == 50:
+        i = 0
+        print("trip:",trip)
+    utime.sleep_ms(10)
+```
+
+* 输出：
+```log
+...
+Testing fheartbeat  ...
+trip: {0: 3719, 1: 3720, 2: 3719, 3: 3720, 4: 3717, 5: 3734, 6: 3726, 7: 3732, 8: 3730, 9: 3732, 10: 3724, 11: 3724, 12: 3732, 13: 3732, 14: 3734, 15: 3730, 16: 3726, 17: 3719, 18: 3734, 19: 3728, 20: 3724, 21: 3728, 22: 3732, 23: 3720, 24: 3732, 25: 3724, 26: 3720, 27: 3720, 28: 3724, 29: 3719, 30: 3717, 31: 3726, 32: 3720, 33: 3722, 34: 3719, 35: 3734, 36: 3722, 37: 3717, 38: 3722, 39: 3720, 40: 3719, 41: 3720, 42: 3711, 43: 3717, 44: 3734, 45: 3724, 46: 3722, 47: 3720, 48: 3724, 49: 3717}
+trip: {0: 3732, 1: 3720, 2: 3720, 3: 3713, 4: 3719, 5: 3719, 6: 3717, 7: 3720, 8: 3717, 9: 3717, 10: 3719, 11: 3717, 12: 3724, 13: 3724, 14: 3720, 15: 3720, 16: 3720, 17: 3724, 18: 3713, 19: 3719, 20: 3719, 21: 3715, 22: 3713, 23: 3713, 24: 3720, 25: 3717, 26: 3713, 27: 3717, 28: 3720, 29: 3709, 30: 3722, 31: 3715, 32: 3719, 33: 3719, 34: 3715, 35: 3709, 36: 3724, 37: 3719, 38: 3717, 39: 3717, 40: 3719, 41: 3711, 42: 3728, 43: 3720, 44: 3719, 45: 3724, 46: 3717, 47: 3717, 48: 3717, 49: 3732}
+...
+
+```
+
+<br>
+
+## 四、通信协议
+主控芯片通过ADC读取手指侦测心跳传感器的电压值数据。
+
+## 五、工作原理
+当手指放在发射器与接收器之间，红外发射LED发射的光将穿过手指，到被接收器接收。而血压会随着脉搏变化，导致红外接收器接收到的光通量也会随之变化，因此可以通过红外光接收的情况来统计监测心跳。其大概的电原理示意图如下：
+<div align="center">
+<img src=./../../docs/images/fheatbeat-princ.png  width=70%/>
+</div>
+
+## 参考文献及购买链接
+[1] [商品链接](https://item.taobao.com/item.htm?spm=a1z0d.6639537.1997196601.3.7a0b7484Tdo3id&id=571175470073)

haas_lib_bundles/python/libraries/fheartbeat/fheartbeat.py

+"""
+Copyright (C) 2015-2021 Alibaba Group Holding Limited
+
+    HaaS Python driver for fheartbeat
+
+    Author: HaaS
+    Date:   2022/05/15
+"""
+
+from driver import ADC
+
+class FHEARTBEAT(object):
+    """
+    This class implements FHEARTBEAT chip's defs.
+    """
+
+    def __init__(self, adcObj):
+        self._adcObj = None
+        if not isinstance(adcObj, ADC):
+            raise ValueError("parameter is not an adcObj object")
+        self._adcObj = adcObj
+
+    def getVoltage(self):
+        if self._adcObj is None:
+            raise ValueError("invalid ADC object")
+        value = self._adcObj.readVoltage()
+        return value