Diff: vga640x400.h

Revision:

4:3f0bd68a4dda

Parent:

0:78fa88bb24cb

Child:

5:c34147b65f7d

--- a/vga640x400.h	Wed Aug 10 11:24:28 2011 +0000
+++ b/vga640x400.h	Wed Aug 10 11:31:23 2011 +0000
@@ -1,14 +1,22 @@
 #ifndef VGA640X400_H
 #define VGA640X400_H
 
-extern unsigned char text_buffer[80*25];
-extern unsigned char *font;
+extern unsigned char text_buffer[80*25]; ///< 80x25 screen buffer, i.e. 25 lines of 80 characters.
+extern unsigned char *font;              ///< Pointer to the user supplied font.
+                                         ///< Each character is 8 pixels wide and 16 pixels high.
+                                         ///< The font consists of 16 groups of 256 bytes.
+                                         ///< i.e. 256 times the first byte of each character, then
+                                         ///< 256 times second byte of each character, and so on.
+                                         ///< This differs from the most common way bitmap fonts are
+                                         ///< ordered, so you have to preprocess your font data first.
+                                    
 
-// Always call this as the very first thing in your application
-// as it resets the CPU clock to 100MHz. It also resets UART0
-// to 9600 baud with the new clock. All other peripherals are off
-// after a call to init_vga()
-
+/** Initialize the VGA signal
+ *
+ * This function should be the very first thing you call, before doing anything else.
+ * It turns off all peripherals, sets the main clock to 100MHz (instead of the 96MHz default of the mbed)
+ * and switches on PWM, I2S and DMA.
+ */
 void init_vga(void);
 
 #endif
\ No newline at end of file