From 06243aaa007be6e380915f18ab4c8e3234ad8a06 Mon Sep 17 00:00:00 2001
From: ladyada <limor@ladyada.net>
Date: Mon, 1 Oct 2018 22:32:25 -0400
Subject: [PATCH 1/2] make I2C init more standard, move try/except into the
 wakeup location

---
 adafruit_am2320.py            |  7 +++++--
 examples/am2320_simpletest.py | 15 ++++-----------
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/adafruit_am2320.py b/adafruit_am2320.py
index 3e38195..560bebf 100644
--- a/adafruit_am2320.py
+++ b/adafruit_am2320.py
@@ -90,7 +90,10 @@ def __init__(self, i2c_bus, address=AM2320_DEFAULT_ADDR):
     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 +106,7 @@ 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])
diff --git a/examples/am2320_simpletest.py b/examples/am2320_simpletest.py
index 60a3037..817b36f 100644
--- a/examples/am2320_simpletest.py
+++ b/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)

From 60ef01ab4e365d032b692ec4261b2664456c3f2d Mon Sep 17 00:00:00 2001
From: ladyada <limor@ladyada.net>
Date: Mon, 1 Oct 2018 22:40:21 -0400
Subject: [PATCH 2/2] add init retries

---
 adafruit_am2320.py | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/adafruit_am2320.py b/adafruit_am2320.py
index 560bebf..59fac53 100644
--- a/adafruit_am2320.py
+++ b/adafruit_am2320.py
@@ -85,7 +85,15 @@ 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: