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

// Calculate the time per bit
#define BAUD_RATE 115200
#define US_PER_BIT 1000000/BAUD_RATE

// Send a single character or byte.
void softSerial_sendChar(char c) {
    cli();
    
    // Send start bit
    PORTD &= ~(1<<PD2);
    _delay_us(US_PER_BIT);
    
    // Send 8 data bits
    for (uint8_t i=0; i<8; i++) {
        if (c & 1) {
            PORTD |= (1<<PD2);
        } else {
            PORTD &= ~(1<<PD2);
        }
        _delay_us(US_PER_BIT);
        c=c>>1;
    }
    
    // Send 2 stop bits
    PORTD |= (1<<PD2);  
    _delay_us(2*US_PER_BIT);
    
    sei();    
}

// Send a string.
void softSerial_sendStr(char* text) {
    char c;
    while ((c=*text)) {
        softSerial_sendChar(c);
        text++;
    }
}