Add LED_PIN definition.

Author: tylercrumpton

README.md

@@ -43,6 +43,7 @@ Pins can be referenced as follows:
 | Digital  | D0 - D13        |
 | Analog   | A0 - A5         |
 | i2c      | SDA, SCL        |
+} LED pin  | LED_PIN         |
 
 Setting up the SPI pins is very simple, too:
 

pyduinoincludes/io.py

@@ -31,6 +31,9 @@
 A4 = 6
 A5 = 7
 
+# User-controlled LED
+LED_PIN = 18
+
 # List of pin assignments that can be iterated over in GPIO-order (i.e. GPIO 0 is 16, GPIO 1 is 17, etc...)
 GPIO_TO_IO_LIST = (16,17,20,5,23,6,7,12,0,19,21,37,4,22,9,8)