增加TVOC检测库，修复ASR声音采集

boards/default_src/micropython/origin/build/lib/tvoc07s.py

@@ -0,0 +1,39 @@
+"""
+TVOC
+
+Micropython library for the TVOC(UART)
+=======================================================
+@dahanzimin From the Mixly Team 
+"""
+import time
+
+class TVOC:
+    def __init__(self, uart):
+        self._uart = uart
+        self._uart.init(baudrate=9600)
+        self._tvoc = (0, 0 ,0)  #TVOC mg/m3, CH2O mg/m3, C02 ppm
+        self._flag = False
+        if not self._chip_id():
+            raise AttributeError("Cannot find a TOVC")
+
+    def _rreg(self):
+        '''Read data'''
+        if self._uart.any():
+            eec = 0
+            buf = self._uart.read(9)
+            for i in buf[:8]:
+                eec += i
+            if (eec & 0xFF) == buf[8] and buf[0] == 0x2C:
+                self._tvoc=((buf[2] << 8 | buf[3]) * 0.001, (buf[4] << 8 | buf[5]) * 0.001, buf[6] << 8 | buf[7] )
+                return True
+
+    def _chip_id(self):
+        for _ in range(5):
+            if self._rreg():
+                return True
+            time.sleep(1)
+        return False
+
+    def read(self):
+        self._rreg()
+        return  self._tvoc