avr_lcd.cpp

// 8mhz internal
#define F_CPU                   8000000

#include <avr/io.h>
#include <stdio.h>
#include <util/delay.h>

// 8 bit LCD logic pins
#define LCD_DATA_DIRECTION      DDRB
#define LCD_DATA_PORT           PORTB
#define LCD_DATA_INPUT          PINB

// LCD control pins
#define LCD_CONTROL_DIRECTION   DDRC
#define LCD_CONTROL_PORT        PORTC
#define LCD_RS                  PC5
#define LCD_RW                  PC4
#define LCD_E                   PC3

// Test LED
#define LED_DIRECTION           DDRC
#define LED_PORT                PORTC
#define LED                     PC2

// Bitwise macros
#define BYTE(bit) (1 << (bit))
#define SET(b, bit) ((b) |= BYTE(bit))
#define UNSET(b, bit) ((b) &= ~BYTE(bit))

// Configuration
#define LCD_STROBE_DURATION     1

// Used for stdout
FILE lcd_file;

typedef unsigned char byte;
typedef volatile byte addr;

class LCD {
public:
    
    LCD(addr *data_dir, addr *data_port, addr *data_pin,
        addr *ctrl_dir, addr *ctrl_port,
        byte rs, byte rw, byte e) :
    data_dir(data_dir), data_port(data_port), data_pin(data_pin),
    ctrl_dir(ctrl_dir), ctrl_port(ctrl_port),
    rs(rs), rw(rw), e(e)
    {
        *ctrl_dir = BYTE(LCD_RS) | BYTE(LCD_RW) | BYTE(LCD_E);
        *data_dir = (byte)0xFF;
    }
    
    void selectDR() {
        SET(*ctrl_port, rs);
    }
    
    void selectIR() {
        UNSET(*ctrl_port, rs);
    }
    
    void setRead(bool read) {
        if (read)   { SET(*ctrl_port, rw); }
        else        { UNSET(*ctrl_port, rw); }
    }
    
    void setEnable(bool enable) {
        if (enable) { SET(*ctrl_port, e); }
        else        { UNSET(*ctrl_port, e); }
    }
    
    void strobeEnable() {
        setEnable(true);
        _delay_ms(LCD_STROBE_DURATION);
        setEnable(false);
    }
    
    unsigned char readBusyFlag() {
        // direction = input
        *data_dir = 0;
        
        setRead(true);
        selectIR();
        
        setEnable(true);
        _delay_ms(LCD_STROBE_DURATION);
        unsigned char ret = *data_pin;
        setEnable(false);
        
        // direction = output
        *data_dir = 0xFF;
        
        return ret;
    }
    
    void busyWait() {
        while ((readBusyFlag() & 0x80) == 0x80) {}
    }
    
    void sendCommand(unsigned char cmd) {
        busyWait();
        
        *data_port = cmd;
        setRead(false);
        selectIR();
        
        strobeEnable();
        
        *data_port = 0;
    }
    
    void sendCharacter(char character) {
        busyWait();
        
        *data_port = character;
        
        setRead(false);
        selectDR();
        strobeEnable();
        
        *data_port = 0;
    }
    
    void sendString(const char *string) {
        char *str = (char *)string;
        while (*str != '\0') {
            sendCharacter(*str++);
        }
    }
    
protected:
    addr *data_dir, *data_port, *data_pin;
    addr *ctrl_dir, *ctrl_port;
    byte rs, rw, e;
};

int lcd_put(char c, FILE *f) {
    if (c == '\n') {
        return 0;
    }
    
    LCD *lcd = (LCD *)f->udata;
    if (lcd != NULL) {
        lcd->sendCharacter(c);
    }
    
    return 0;
}

int main() {
    LED_DIRECTION = 0xFF;
    SET(LED_PORT, LED);
    
    LCD m(&LCD_DATA_DIRECTION, &LCD_DATA_PORT, &LCD_DATA_INPUT,
          &LCD_CONTROL_DIRECTION, &LCD_CONTROL_PORT,
          LCD_RS, LCD_RW, LCD_E);
    
    lcd_file.put = lcd_put;
    lcd_file.udata = &m;
    lcd_file.flags = __SWR;
    stdout = &lcd_file;
    
    m.sendCommand(0b00111000); // 2 line display, 8 bit logic config
    m.sendCommand(0b00000010); // return cursor to 0
    m.sendCommand(0b00001111); // cursor on, cursor blinking, display on
    
    puts("hi dan!");
    
    while(1) {}
    
    return 0;
}