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torben |
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/*
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* LCD interface example
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* Uses routines from delay.c
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* This code will interface to a standard LCD controller
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* like the Hitachi HD44780. It uses it in 4 or 8 bit mode
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*
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*/
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#include <pic18.h>
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#include "lcd.h"
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#include "delay.h"
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static bit fourbit; // four or eight bit mode?
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#ifdef CHECKBUSY
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unsigned char
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lcd_read_cmd_nowait(void)
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{
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unsigned char c, readc;
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LCD_DATA_TRIS = INPUT_DATA;
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LCD_RW = 1; // Read LCD
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asm("nop"); // short propagation delay
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asm("nop"); // short propagation delay
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if (fourbit)
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{
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LCD_STROBE_READ(readc); // Read high nibble
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// Move 4 bits to high nibble while zeroing low nibble
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c = ( ( readc << 4 ) & 0xF0 );
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LCD_STROBE_READ(readc); // Read low nibble
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c |= ( readc & 0x0F ); // Or in 4 more bits to low nibble
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}
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else
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{
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LCD_STROBE_READ(readc);
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c = readc;
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}
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LCD_RW = 0; // Return to default mode of writing LCD
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LCD_DATA_TRIS = OUTPUT_DATA; // Return to default mode of writing LCD
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return(c);
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}
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void
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lcd_check_busy(void) // Return when the LCD is no longer busy, or we've waiting long enough!
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{
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// To avoid hanging forever in event there's a bad or
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// missing LCD on hardware. Will just run SLOW, but still run.
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unsigned int retry;
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unsigned char c;
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for (retry=1000; retry-- > 0; ) {
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c = lcd_read_cmd_nowait();
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if (0==(c&0x80)) break; // Check busy bit. If zero, no longer busy
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}
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}
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#endif
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/* send a command to the LCD */
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void
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lcd_cmd(unsigned char c)
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{
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LCD_WAIT; // may check LCD busy flag, or just delay a little, depending on lcd.h
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if (fourbit)
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{
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LCD_DATA = ( ( c >> 4 ) & 0x0F );
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LCD_STROBE();
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LCD_DATA = ( c & 0x0F );
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LCD_STROBE();
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}
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else
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{
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LCD_DATA = c;
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LCD_STROBE();
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}
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}
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/* send data to the LCD */
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void
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lcd_data(unsigned char c)
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{
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LCD_WAIT; // may check LCD busy flag, or just delay a little, depending on lcd.h
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LCD_DATA = 0;
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LCD_RS = 1;
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if (fourbit)
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{
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LCD_DATA |= ( ( c >> 4 ) & 0x0F );
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LCD_STROBE();
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LCD_DATA &= 0xF0;
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LCD_DATA |= ( c & 0x0F );
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LCD_STROBE();
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}
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else
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{
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LCD_DATA = c;
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LCD_STROBE();
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}
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LCD_RS = 0;
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}
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/* write a string of chars to the LCD */
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void
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lcd_puts(const char * s)
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{
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while(*s)
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lcd_data(*s++);
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}
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/* initialize the LCD */
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void
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lcd_init(unsigned char mode)
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{
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char init_value;
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fourbit = 0;
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if (mode == FOURBIT_MODE){
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fourbit = 1;
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init_value = 0x3;
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}else{
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init_value = 0x3F;
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}
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LCD_RS = 0;
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LCD_EN = 0;
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LCD_RW = 0;
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LCD_RS_TRIS = OUTPUT_PIN;
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LCD_EN_TRIS = OUTPUT_PIN;
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LCD_RW_TRIS = OUTPUT_PIN;
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LCD_DATA_TRIS = OUTPUT_DATA;
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DelayMs(15);
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LCD_DATA = init_value;
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LCD_STROBE();
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DelayMs(5);
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LCD_DATA = init_value;
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LCD_STROBE();
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DelayUs(200);
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LCD_DATA = init_value;
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LCD_STROBE();
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if (fourbit){
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LCD_WAIT; //may check LCD busy flag, or just delay a little, depending on lcd.h
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LCD_DATA = 0x2; // Set 4-bit mode
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LCD_STROBE();
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lcd_cmd(0x28); // Function Set
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}else{
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lcd_cmd(0x38);
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}
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lcd_cmd(0xF); //Display On, Cursor On, Cursor Blink
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lcd_cmd(0x1); //Display Clear
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lcd_cmd(0x6); //Entry Mode
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lcd_cmd(0x80); //Initialize DDRAM address to zero
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}
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