avr dmx implementation

main.c

#define F_CPU 8000000UL

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

volatile uint8_t universe[513];
uint16_t i;

#ifndef _BITFIELD_
#define _BITFIELD_

typedef struct
   {
      uint8_t B0 : 1;
      uint8_t B1 : 1;
      uint8_t B2 : 1;
      uint8_t B3 : 1;
      uint8_t B4 : 1;
      uint8_t B5 : 1;
      uint8_t B6 : 1;
      uint8_t B7 : 1;
   } bitfield;

#ifdef PORTB
#define _PORTB (*((volatile bitfield*)&PORTB))
#define _PINB  (*((volatile bitfield*)&PINB))
#define _DDRB  (*((volatile bitfield*)&DDRB))
#endif // PORTB


#endif // _BITFIELD_


int main(void) {
  cli();

  UBRR0L = 1;
  UBRR0H = 0;
  UCSR0C = 0b00001110;
  UCSR0B = 0b10011000; // enabled value, disabled value is UCSR0B = 0b10010000;
  UCSR0A = 0x00;

  sei();

  for(int x = 1; x < 513; x++) {
    universe[x] = 255;
  }

  while (1) {
    _DDRD.B1 = 1;
    _PORTD.B1 = 0;
    UCSR0B = 0b10010000; // This disables the UART TX so we can use GPIO to hold it low for BREAK
    _delay_us(92);

    _PORTD.B1 = 1; // Pull high
    _delay_us(10); // We get 2 us as the UART enables
    UCSR0B = 0b10011000; // Re-enable UART TX

    while (!(UCSR0A & 0b00100000)); // Wait for port to be ready
    UDR0 = 0x00; // Null start code
    
    for (i = 1; i < 513; i++) {
      while (!(UCSR0A & 0b00100000));
      UDR0 = universe[i];
    }

    // Wait for the last byte to be sent
    while (!(UCSR0A & 0b00100000));


  }

  return 0;

}