API.md

@@ -23,7 +23,22 @@ Example:
 <pre>
 (seesaw:digital-read-p 'PA10)
 </pre>
-Would read pin PA10 and if logical high "1" would return T, otherwise return nil..
+Would read pin PA10 and if logical high "1" would return T, otherwise return nil.
+
+## seesaw:digital-write
+Writes a bit to GPIO returning a T or NIL.
+Note, you should set the pin direction to output, before writing.
+Output is set to binary one for 'set 'on 'h and 'high.
+Output is set to binary zero for 'clr 'off 'l and 'low. 
+Parameters:
+<pre>
+(seesaw:digital-write pin state)
+</pre>
+Example:
+<pre>
+(seesaw:digital-write 'PA27 'on)
+</pre>
+Would light the active-high LED on the adafruit seesaw breakout board, assuming PA27 had previously been set to output.
 
 ## seesaw:id-read
 Read the hardware ID of the chip, which should always be 0x55 aka 85 decimal.  Parameters: