Diff: freetronicsLCDShield.h

Revision:

7:56d8df0eb209

Parent:

6:ac481535732f

--- a/freetronicsLCDShield.h	Sun Jul 02 15:05:19 2017 +0000
+++ b/freetronicsLCDShield.h	Sun Jul 02 15:26:57 2017 +0000
@@ -1,5 +1,7 @@
 /* mbed freetronicsLCDShield Library, written by Koen J.F. Kempeneers
  * kkempeneers@skynet.be
+ * Improved button support added by John Bailey 
+ * jdb__mbed(at)anotherdimension.net
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -26,9 +28,9 @@
 #define LEFT  0
 #define RIGHT 1
 
+/** Number of detectable buttons on the shield, Left, Right, Up, Down, plus one for "No button" */
 #define FREETRONICSLCDSHIELD_BUTTON_COUNT 5
 
-
 /** 
   * Provides full LCD support for the HD44780 compatible LCD on the arduino shaped shield.
   * http://www.freetronics.com/products/lcd-keypad-shield#.UnIr6_nkq0M
@@ -170,10 +172,22 @@
         
         /** Reads the status of the buttons
          * 
-         * 
+         * This function returns the ADC value of the input connected to the buttons.  When no button is pressed, this input is pulled high.
+         * If any button is pressed, the input is connected to ground via a resistor & the function will return a value less than 1.0, 
+         * depending on the button.  Approximate values (sourced from the schematic) are:
+         *  Left:  2.47V -> ADC 0.748
+         *  Down:  1.61V -> ADC 0.488
+         *  Up:    0.71V -> ADC 0.215
+         *  Right: 0.00V -> ADC 0.000
+         * Note that as ADC inputs are referenced to 3.3V, the select button cannot be read (as the voltage when this buttong is pressed is 3.62V,
+         * saturating the input and indistinguishable from no button being pressed.
          */  
         float readButton(void);
              
+        /** Determines which of the buttons is currently pressed
+         *
+         * Note that the shield design means that multi-button detection is not practical 
+         */
         ShieldButton pressedButton(void);     
              
     protected:
@@ -181,6 +195,7 @@
         virtual int _putc(int value);
         virtual int _getc();
                 
+        /** Lower thresholds for the ADC value for each push button on the shield */
         static const float buttonThresholds[FREETRONICSLCDSHIELD_BUTTON_COUNT];
 };