sipo_lcd_shift.c

#define SIPO PORTB

#define STB PB3
#define SPIN PB4
#define CLK PB5

//Rememeber DDRB |= (1<<STB) | (1<<SPIN) | (1<<CLK); //must be done in main() so as set these pins as output.

void send_nibble(unsigned char x)  //try to make this also inline if necessary
{
	x |= (1<<en); // set en pin as 1
	
	SIPO_send(x); //send the data through SIPO
	
	SIPO |= (1<<STB); //after sending enable the STROBE so that data is now available on the data pins

	_delay_ms(1); //give delay of 10ms for enable change CLK
	
	SIPO &= ~(1<<STB);//clear the strobe now

	x &= ~(1<<en); // now make the enable pin of lcd as 0
		
	SIPO_send(x); // again send new data in which only enable pin state of lcd is changed
					
	SIPO |= (1<<STB); //again set the strobe
	_delay_ms(1); //delay 10ms
	SIPO &= ~(1<<STB); // clear the strobe


		//to send a nibble 2 * 80us + 2 * 1ms = 2.16ms total delay
}

void lcd_cmd(unsigned char var)
{
	unsigned char x;

//send higher nibble
	x = 0xf0 & var; //get higher nibble into x  
	
	x &= ~(1<<rs); 	//set the rs pin as 0
	send_nibble(x); //enable pin clocking mechanism is contained in nibble fucntion

//now send lower nibble
	x = 0xf0 & (var<<4);   // now repeat same process for lower nibble
	
	x &= ~(1<<rs); 	
	send_nibble(x);
	
//to send a cmd or data byte delay is 2 * 2.16ms = 4.32ms

//so data rate is 1/4.32ms = 231 char's /second ; good enough for our display
}




void lcd_data(unsigned char var)
{
	unsigned char x;

//send higher nibble
	x = 0xf0 & var;  
	
	x |= (1<<rs); 	
	send_nibble(x);

//now send lower nibble
	x = 0xf0 & (var<<4);  
	
	x |= (1<<rs); 	
	send_nibble(x);

	
}