Add example.

README.rst

@@ -10,7 +10,7 @@ Introduction
     :target: https://discord.gg/nBQh6qu
     :alt: Discord
 
-TODO
+CircuitPython module for the MAX31865 thermocouple amplifier.
 
 Dependencies
 =============
@@ -26,7 +26,7 @@ This is easily achieved by downloading
 Usage Example
 =============
 
-TODO
+See examples/simpletest.py for a demo of the usage.
 
 Contributing
 ============

examples/simpletest.py

@@ -0,0 +1,26 @@
+# Simple demo of the MAX31865 thermocouple amplifier.
+# Will print the temperature every second.
+import board
+import busio
+import time
+
+import adafruit_max31865
+
+
+# Initialize SPI bus and sensor.
+spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
+cs =  board.D5  # Chip select of the MAX31865 board.
+sensor = adafruit_max31865.MAX31865(spi, cs)
+# Note you can optionally provide the thermocouple RTD nominal, the reference
+# resistance, and the number of wires for the sensor (2 the default, 3, or 4)
+# with keyword args:
+#sensor = adafruit_max31865.MAX31865(spi, cs, rtd_nominal=100, ref_resistor=430.0, wires=2)
+
+# Main loop to print the temperature every second.
+while True:
+    # Read temperature.
+    temp = sensor.temperature
+    # Print the value.
+    print('Temperature: {0.3f}C'.format(temp))
+    # Delay for a second.
+    time.sleep(1.0)