I question came to my mind when i was designing a pcb for a home project which includes a lcd (16*2 lcd connected in 4 - bit mode) and an atmega32 i had connected that in this manner:
RS - PB4, E - PB5, RW - GND and D0 to D7 connected to PB0 to PB3 respectively.
Now let's come to the problem i want to interchange the data lines connected to PORTB i.e. I want to connect them in reverse order like this:-
D0 to D7 should now connect to PB7 to PB4 and RS to PB1 , and E to PB2. I can change the position of RS and E but i don't know how can i change the code to send data in this manner to the lcd. Here is the code that i am using for lcd interfacing.
#define F_CPU 8000000UL /* Define CPU Frequency e.g. here 8MHz */
#include <avr/io.h> /* Include AVR std. library file */
#include <util/delay.h> /* Include Delay header file */
#define LCD_Dir DDRB /* Define LCD data port direction */
#define LCD_Port PORTB /* Define LCD data port */
#define RS PB0 /* Define Register Select pin */
#define EN PB1 /* Define Enable signal pin */
void LCD_Command( unsigned char cmnd )
{
LCD_Port = (LCD_Port & 0x0F) | (cmnd & 0xF0); /* sending upper nibble */
LCD_Port &= ~ (1<<RS); /* RS=0, command reg. */
LCD_Port |= (1<<EN); /* Enable pulse */
_delay_us(1);
LCD_Port &= ~ (1<<EN);
_delay_us(200);
LCD_Port = (LCD_Port & 0x0F) | (cmnd << 4); /* sending lower nibble */
LCD_Port |= (1<<EN);
_delay_us(1);
LCD_Port &= ~ (1<<EN);
_delay_ms(2);
}
void LCD_Char( unsigned char data )
{
LCD_Port = (LCD_Port & 0x0F) | (data & 0xF0); /* sending upper nibble */
LCD_Port |= (1<<RS); /* RS=1, data reg. */
LCD_Port|= (1<<EN);
_delay_us(1);
LCD_Port &= ~ (1<<EN);
_delay_us(200);
LCD_Port = (LCD_Port & 0x0F) | (data << 4); /* sending lower nibble */
LCD_Port |= (1<<EN);
_delay_us(1);
LCD_Port &= ~ (1<<EN);
_delay_ms(2);
}
void LCD_Init (void) /* LCD Initialize function */
{
LCD_Dir = 0xFF; /* Make LCD port direction as o/p */
_delay_ms(20); /* LCD Power ON delay always >15ms */
LCD_Command(0x02); /* send for 4 bit initialization of LCD */
LCD_Command(0x28); /* 2 line, 5*7 matrix in 4-bit mode */
LCD_Command(0x0c); /* Display on cursor off*/
LCD_Command(0x06); /* Increment cursor (shift cursor to right)*/
LCD_Command(0x01); /* Clear display screen*/
_delay_ms(2);
}
void LCD_String (char *str) /* Send string to LCD function */
{
int i;
for(i=0;str[i]!=0;i++) /* Send each char of string till the NULL */
{
LCD_Char (str[i]);
}
}
void LCD_String_xy (char row, char pos, char *str) /* Send string to LCD with xy position */
{
if (row == 0 && pos<16)
LCD_Command((pos & 0x0F)|0x80); /* Command of first row and required position<16 */
else if (row == 1 && pos<16)
LCD_Command((pos & 0x0F)|0xC0); /* Command of first row and required position<16 */
LCD_String(str); /* Call LCD string function */
}
void LCD_Clear()
{
LCD_Command (0x01); /* Clear display */
_delay_ms(2);
LCD_Command (0x80); /* Cursor at home position */
}
int main()
{
LCD_Init(); /* Initialization of LCD*/
LCD_String_xy(0, 10, "Hello World");
while(1);
}
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