/*
 * 	startup.c
 *
 */

 #import "delay.h"

 #define GPIO_E	0x40021000
 #define GPIO_E_MODER ((volatile unsigned int *) GPIO_E)
 #define GPIO_E_OTYPER ((volatile unsigned short *) GPIO_E + 0x4)
 #define GPIO_E_OSPEEDR ((volatile unsigned int *) GPIO_E + 0x8)
 #define GPIO_E_PUPDR ((volatile unsigned int *) GPIO_E + 0xC)
 #define GPIO_E_IDR_LOW ((volatile unsigned char*) GPIO_E + 0x10)
 #define GPIO_E_IDR_HIGH ((volatile unsigned char*) GPIO_E + 0x11)
 #define GPIO_E_ODR_LOW ((volatile unsigned char*) GPIO_E + 0x14)
 #define GPIO_E_ODR_HIGH ((volatile unsigned char*) GPIO_E + 0x15)
 #define B_E      0b01000000
 #define B_SELECT 0b00000100
 #define B_RW     0b00000010
 #define B_RS	  0b00000001

void startup(void) __attribute__((naked)) __attribute__((section (".start_section")) );

void startup ( void )
{
__asm volatile(
	" LDR R0,=0x2001C000\n"		/* set stack */
	" MOV SP,R0\n"
	" BL main\n"				/* call main */
	"_exit: B .\n"				/* never return */
	) ;
}

void ascii_ctrl_bit_set( unsigned char x )
{
	*GPIO_E_ODR_LOW |= (B_SELECT | x) ;
}

void ascii_ctrl_bit_clear( unsigned char x )
{
	*GPIO_E_ODR_LOW &= ( B_SELECT  | ~x );
}


unsigned char ascii_read_controller( void )
{
	ascii_ctrl_bit_set( B_E );
	delay_250ns();
	delay_250ns();
	unsigned char rv = *GPIO_E_IDR_HIGH;
	ascii_ctrl_bit_clear( B_E );
	return rv;
}

void ascii_write_controller( unsigned char byte )
{
	ascii_ctrl_bit_set( B_E );
	*GPIO_E_ODR_HIGH = byte;
	delay_250ns();
	ascii_ctrl_bit_clear( B_E );
}

void ascii_write_cmd( unsigned char command )
{
	ascii_ctrl_bit_clear( B_RS );  //ascii_ctrl_bit_clear( B_RS | B_RW );
	ascii_ctrl_bit_clear( B_RW );
	ascii_write_controller( command );
}

void ascii_write_data( unsigned char data )
{
	ascii_ctrl_bit_set( B_RS );
	ascii_ctrl_bit_clear( B_RW );
	ascii_write_controller( data );
}

unsigned char ascii_read_status( void )
{
	*GPIO_E_MODER = 0x00005555; //configure GPIO_E to become an inport so we can read from it
	ascii_ctrl_bit_clear( B_RS );
	ascii_ctrl_bit_set( B_RW );
	unsigned char rv = ascii_read_controller();
	*GPIO_E_MODER = 0x55555555; //turn GPIO_E back to an outport
	return rv;
}

unsigned char ascii_read_data( void )
{
	*GPIO_E_MODER = 0x00005555; //configure GPIO_E to become an inport so we can read from it
	ascii_ctrl_bit_set( B_RS | B_RW ); //Set both RS and RW bits to be '1'
	unsigned char rv = ascii_read_controller();
	*GPIO_E_MODER = 0x55555555; //turn GPIO_E back to an outport
	return rv;
}

void ascii_command( unsigned short command )
{
	while ( (ascii_read_status() & 0x80) == 0x80 ) {} //Wait for B_E to become '0' to indicate that the ASCII display is ready to receive a command (that it isn't busy)
	delay_mikro( 8 );
	ascii_write_cmd( (char)(command & 0b0011111111) ); //must reset two first bits (they're not used in this function, only to indicate what delay to pick in switch statement below)
													  //and convert to byte (ascii_write_cmd takes a byte, not a short)
	switch( command ) {
		case 0b0000000001 ... 0b0000000011: //For clear display and return home
			delay_milli(2); //For commands that require <2ms delay;
			break;
		case 0b0010000000 ... 0b0011111111: //For 'read address' and 'read status'
			break; //For command that doesn't require a delay
		default: //For display control, function set, address, etc
			delay_mikro(50); //default case for all the other commands that require 39 or 43us delay minimum (and we use 50us as a safety measure to ensure it works)
	}
}

void ascii_write_char( char c )
{
	while ( (ascii_read_status() & 0x80) == 0x80 ) {} //Wait for statusflag to indicate that asciidisplay is not busy
	delay_mikro(8);
	ascii_write_data( c );
	delay_mikro(50);
}

void ascii_gotoxy( unsigned int x, unsigned int y )
{
	unsigned int address = x - 1; //Convert from 1-indexing to 0-indexing
	if( y == 2 ) { //If writig to second line
		address += 0x40; //offset address with 0x40 (64) to start writing on the second row (each row is 64 long, but no scroll is used so we only see 20 per row))
	}
	ascii_write_cmd( 0x80 | address );
}


void app_init( void )
{
	*GPIO_E_MODER = 0x55555555;
	ascii_ctrl_bit_clear(0b11111111); //reset all before execution
}

void ascii_init(  )
{
	ascii_command( 1 ); //Clear screen
	ascii_command( 0b0000111000 ); //Init with 2 rows, 5x8 dots per letter
	ascii_command( 0b0000001110 ); //Turn on display, show marker
	ascii_command( 0b0000000110 ); //possibly wrong? idk, addressing with increment, no shift of buffer
}



int main(int argc, char **argv)
{
	char *s;
	char test1[] = "Alfanumerisk";
	char test2[] = "Display - test";

	app_init();
	ascii_init();
	ascii_gotoxy(1, 1);
	s = test1;
	while( *s )
	{
		ascii_write_char( *s++ );
	}
	ascii_gotoxy(1,2);
	s = test2;
	while( *s )
	{
		ascii_write_char( *s++ );
	}
	return 0;


}