Задача: Управление графическим дисплеем

Исходный материал: PIC16f628a, LCD2x16

Схема подключения дисплея (кварц не подключен, но предполагается, что он есть):

Следующий шаг — написание функций управления дисплеем. Я просто взял файлы из директории samples папки компилятора и переделал под себя.

Файл lcd.c

/*
* LCD interface example
* Uses routines from delay.c
* This code will interface to a standard LCD controller
* like the Hitachi HD44780. It uses it in 4 bit mode, with
* the hardware connected as follows (the standard 14 pin
* LCD connector is used):
*
* PORTD bits 0-3 are connected to the LCD data bits 4-7 (high nibble)
* PORTA bit 3 is connected to the LCD RS input (register select)
* PORTA bit 1 is connected to the LCD EN bit (enable)
*
* To use these routines, set up the port I/O (TRISA, TRISD) then
* call lcd_init(), then other routines as required.
*
*/

#ifndef _XTAL_FREQ
// Unless specified elsewhere, 4MHz system frequency is assumed
#define _XTAL_FREQ 4000000
#endif

#include <htc.h>
#include "lcd.h"

#define LCD_RS RA1
#define LCD_RW RA2
#define LCD_EN RA3

#define LCD_DATA PORTB

#define LCD_STROBE() ((LCD_EN = 1),(LCD_EN=0))

/* write a byte to the LCD in 4 bit mode */

void
lcd_write(unsigned char c)
{
__delay_us(40);
LCD_DATA = ( ( c >> 4 ) & 0x0F );
LCD_STROBE();
LCD_DATA = ( c & 0x0F );
LCD_STROBE();
}

/*
* Clear and home the LCD
*/

void
lcd_clear(void)
{
LCD_RS = 0;
lcd_write(0x1);
__delay_ms(2);
}

/* write a string of chars to the LCD */

void
lcd_puts(const char * s)
{
LCD_RS = 1; // write characters
while(*s)
lcd_write(*s++);
}

/* write one character to the LCD */

void
lcd_putch(char c)
{
LCD_RS = 1; // write characters
lcd_write( c );
}

/*
* Go to the specified position
*/

void
lcd_goto(unsigned char pos)
{
LCD_RS = 0;
lcd_write(0x80+pos);
}

/* initialise the LCD - put into 4 bit mode */
void
lcd_init()
{
char init_value;

CMCON = 0x07; // Disable analog pins on PORTA

init_value = 0x3;
TRISA=0;
TRISB=0;
LCD_RS = 0;
LCD_EN = 0;
LCD_RW = 0;

__delay_ms(15); // wait 15mSec after power applied,
LCD_DATA = init_value;
LCD_STROBE();
__delay_ms(5);
LCD_STROBE();
__delay_us(200);
LCD_STROBE();
__delay_us(200);
LCD_DATA = 2; // Four bit mode
LCD_STROBE();

lcd_write(0x28); // Set interface length
lcd_write(0xF); // Display On, Cursor On, Cursor Blink
lcd_clear(); // Clear screen
lcd_write(0x6); // Set entry Mode
}

и файл lcd.h

/*
* LCD interface header file
* See lcd.c for more info
*/

/* write a byte to the LCD in 4 bit mode */

extern void lcd_write(unsigned char);

/* Clear and home the LCD */

extern void lcd_clear(void);

/* write a string of characters to the LCD */

extern void lcd_puts(const char * s);

/* Go to the specified position */

extern void lcd_goto(unsigned char pos);

/* intialize the LCD - call before anything else */

extern void lcd_init(void);

extern void lcd_putch(char);

/* Set the cursor position */

#define lcd_cursor(x) lcd_write(((x)&0x7F)|0x80)

Ну и, наконец, тестовая программа

#include <htc.h>
#include "lcd.h"
#define _XTAL_FREQ 4000000

__CONFIG(WDTDIS & UNPROTECT & MCLREN & LVPDIS & HS);

void main() {
lcd_init();
lcd_goto(0); // select first line
lcd_puts("PIC manual");
lcd_goto(0x40); // Select second line
lcd_puts("SARGE.PP.UA");

for(;;);

}