UART on Arduino mega with registers printing boxes and question marks

[mahesh_namboodiri]

I tried to implement UART by using registers on Arduino mega. But i'm not getting any significant output. The same code works on Atmega 128 for some reason.

#define BAUD 9600
#define UBRR_VALUE ((16000000 / (16UL * BAUD)) - 1)
#include <stdio.h>
#include <avr/io.h>

uint16_t x;

void UART_init(){

  UCSR0C|=(1<<UCSZ00)|(1<<UCSZ01); //8 bit data
  UBRR0H = (uint8_t)(UBRR_VALUE >> 8);
  UBRR0L|=(uint8_t)(UBRR_VALUE); //9600 Baud rate
  UCSR0B|=(1<<TXEN0)|(1<<RXEN0);  //UART1 Tx Rx enable
}




void UART_send(char y){
  
  while(!(UCSR0A && (1<<UDRE0))); //Check if Tx buffer is empty.
  UDR0=y;
}


int main(){
  UART_init();
  while(1){
    UART_send('p');
    _delay_ms(100);
  }
}

This prints question marks, and any integer type that I send prints boxes. I have verified the baud rate to be correct. what might be the error?

[westfw]

It's possible that the MEGA bootloader leaves USART0 partially configured.
Be sure to initialize ALL of the control registers; especially U2X0 in UCSR0A
(that also means you should use UCSRC = xxx and UCSR0B = yyy instead of the |= form (and UBRR0L too!))

[mahesh_namboodiri]

I did so. The only result is that it is now able to print characters on the serial terminal.
My intention is to send hexadecimals. Is that possible ? I really can't see any error to be frank.

[b707]

@mahesh_namboodiri

now able to print characters...
My intention is to send hexadecimals.

Is this a big difference?

Hexadecimal is not a new type of data, it is just a representation of the bytes, as well a chars.

try this:

int main(){
  UART_init();
  while(1){
    UART_send(0x30);    // you should receive '0' in Monitor
    _delay_ms(100);
  }
}