the gLCD control code

#include <avr/interrupt.h>
#include <glcd.h>
//----------------------------------------------------------------------
// GLCD Function - Implementation
//----------------------------------------------------------------------
// to initialise the LCD
void GlcdInit( void )
{
  // This function must be provided by the user.
  GlcdInitPort();
	// send different controlcommand to the LCD (datasheet for details)
	// internal Reset
	GlcdSendCmd( 0xE2 );
	// ADC select
	GlcdSendCmd( 0xA0 ) ;
	// COM output scan direction = revers
	GlcdSendCmd( 0xC8 );
	// LCD drive voltage bias ratio
	GlcdSendCmd( 0xA2 );
	// no idea
	GlcdSendCmd( 0x2F );
	// no idea
	GlcdSendCmd( 0x26 );
	// select booster ratio
	GlcdSendCmd( 0xF8 );
	// no idea
	GlcdSendCmd( 0x00 );
	// set output voltage
	GlcdSendCmd( 0x81 );
	// no idea
	GlcdSendCmd( 0x09 );
	// read-modify-write
	GlcdSendCmd( 0xE0 );
	// display on
	GlcdSendCmd( 0xAF );
	return;
}
//--------------------
// Set the position for the next output, for text e. g.
// the y-value is round down to a 8like value (0,8,16,24...56)
// parameter: x = x-coordinate 0...127; y = y-coordinate 0...63
void GlcdSetPos( uint8_t x, uint8_t y )
{
	// x-coordinate
	GlcdSendCmd( 0x10 | ( ( x >> 4 ) & 0x0F ) );
	GlcdSendCmd( 0x00 | ( ( x & 0x0F ) ) );
	// y-coordinate
	GlcdSendCmd( 0b10110000 | ( ( y >> 3 ) & 0x0F ) );
  return;
}
//--------------------
// move to the inputline to the actual line on the LCD (srcolleffect)
// parameter: Line = number of the line to goto
void GlcdGotoLine( uint8_t line )
{
	// initial display line
	GlcdSendCmd( 0x40 | ( line & 0x3F ) );
	return;
}
//--------------------
// clears all data on the LCD
void GlcdClear( void )
{
  uint8_t y;
  uint8_t x;
	// the Display consists of 128 * 8 Bytes, which are placed vertical
	// in each byte are bit0 up and bit7 down
	// y-loop (vertical); 8 times, 64 pixels are 8 bytes * 8 bits
	for( y = 0; y < 8; y++ )
	{
    // goto linebegin
		GlcdSetPos( 0, y * 8 );
		// x-Schleife (waagerecht); 128 Pixel sind 128
		for( x = 0; x < 128; x++ )
    {
      // set byte to 0
			GlcdSendData( 0 );
    }
	}
	// set actual position to leftupper corner ( 0, 0 )
	GlcdSetPos( 0, 0 );
	return;
}
//--------------------
// inverse display (dark at bright backround/ bright at dark backround)
// parameter: on = off/on 0/1; 0 = normal (dark at blight backround); 1 = inverse (blight at dark backround)
void GlcdSendCmdReverse( uint8_t bit0 )
{
	// display normal/reverse
	GlcdSendCmd( 0b10100110 + ( bit0 & 0x01 ) );
	return;
}
//--------------------
// turn the display on/off
// parameter: on = on/off 0/1; 0 = display on; 1 = display off (complete dark)
void GlcdSendCmdOn( uint8_t bit0 )
{
	// all pixels on /off
	GlcdSendCmd( 0b10100100 + ( bit0 & 0x01 ) );
	return;
}
//--------------------
// set a Pixel on position x,y at the LCD
// parameter: x = x-coordinate 0...127; y = y-coordinate 0...63
void GlcdSetPixel( uint8_t x, uint8_t y )
{
  uint8_t data;
	// goto position
	GlcdSetPos( x, y );
	// bitmask for the bit (pixel) in the byte
	data = 1 << ( y & 0b00000111 );
	// read the byte, set the bit, write the byte
	GlcdSendData( GlcdReadData() | data );
	return;
}
//--------------------