Merge pull request #5 from ladyada/master

Looks good. Tested on a Pi Zero W and no additional pull ups.

Author: caternuson

adafruit_am2320.py

@@ -85,12 +85,23 @@ class AM2320:
 
     """
     def __init__(self, i2c_bus, address=AM2320_DEFAULT_ADDR):
-        self._i2c = I2CDevice(i2c_bus, address)
+        for _ in range(3):
+            # retry since we have to wake up the devices
+            try:
+                self._i2c = I2CDevice(i2c_bus, address)
+                return
+            except ValueError:
+                pass
+            time.sleep(0.25)
+        raise ValueError("AM2320 not found")
 
     def _read_register(self, register, length):
         with self._i2c as i2c:
             # wake up sensor
-            i2c.write(bytes([0x00]))
+            try:
+                i2c.write(bytes([0x00]))
+            except OSError:
+                pass
             time.sleep(0.01)  # wait 10 ms
 
             # Send command to read register
@@ -103,7 +114,7 @@ def _read_register(self, register, length):
             # print("$%02X => %s" % (register, [hex(i) for i in result]))
             # Check preamble indicates correct readings
             if result[0] != 0x3 or result[1] != length:
-                raise RuntimeError('I2C modbus read failure')
+                raise RuntimeError('I2C read failure')
             # Check CRC on all but last 2 bytes
             crc1 = struct.unpack("<H", bytes(result[-2:]))[0]
             crc2 = _crc16(result[0:-2])

examples/am2320_simpletest.py

@@ -3,18 +3,11 @@
 import busio
 import adafruit_am2320
 
-# can also use board.SDA and board.SCL for neater looking code!
-i2c = busio.I2C(board.D2, board.D0)
+# create the I2C shared bus
+i2c = busio.I2C(board.SCL, board.SDA)
 am = adafruit_am2320.AM2320(i2c)
 
-
 while True:
-    try:
-        print("Temperature: ", am.temperature)
-        print("Humidity: ", am.relative_humidity)
-    except OSError:
-        # These sensors are a bit flakey, its ok if the readings fail
-        pass
-    except RuntimeError:
-        pass
+    print("Temperature: ", am.temperature)
+    print("Humidity: ", am.relative_humidity)
     time.sleep(2)