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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