add analog_in example for blinka and mcp3008

Author: brentru

examples/basics/analog_in.py

@@ -0,0 +1,64 @@
+"""
+'analog_in.py'
+==================================
+Example of sending analog sensor
+values to an Adafruit IO feed.
+
+Author(s): Brent Rubell
+
+Dependencies:
+    - Adafruit_Blinka
+        (https://github.com/adafruit/Adafruit_Blinka)
+    - Adafruit_CircuitPython_MCP3xxx
+        (https://github.com/adafruit/Adafruit_CircuitPython_MCP3xxx)
+"""
+# Import standard python modules
+import time
+
+# import Adafruit Blinka
+import board
+import digitalio
+import busio
+
+# import Adafruit IO REST client
+from Adafruit_IO import Client, Feed, RequestError
+
+# import Adafruit CircuitPython MCP3xxx library
+from adafruit_mcp3xxx import adafruit_mcp3xxx
+
+# Set to your Adafruit IO key.
+# Remember, your key is a secret,
+# so make sure not to publish it when you publish this code!
+ADAFRUIT_IO_KEY = 'YOUR_AIO_KEY'
+
+# Set to your Adafruit IO username.
+# (go to https://accounts.adafruit.com to find your username)
+ADAFRUIT_IO_USERNAME = 'YOUR_AIO_USERNAME'
+# Create an instance of the REST client
+aio = Client(ADAFRUIT_IO_USERNAME, ADAFRUIT_IO_KEY)
+
+try: # if we have a 'analog' feed
+    analog = aio.feeds('analog')
+except RequestError: # create a analog feed
+    feed = Feed(name='analog')
+    analog = aio.create_feed(feed)
+
+# Create an instance of the `busio.spi` class
+spi = busio.SPI(board.SCLK, board.MOSI, board.MISO)
+
+# create the cs (chip select)
+cs = digitalio.DigitalInOut(board.D12)
+# create a mcp3008 object
+mcp = adafruit_mcp3xxx.MCP3008(spi,cs)
+
+# create an an adc (single-ended) on pin 0
+adc_single_ended = adafruit_mcp3xxx.AnalogIn(mcp,0)
+
+while True:
+    sensor_data = adc_single_ended.value
+
+    print('Analog Data -> ', sensor_data)
+    aio.send(analog.key, sensor_data)
+
+    # avoid timeout from adafruit io
+    time.sleep(0.5)