simple arduino code without using avr headers in avr-libc-CodePudding

I have this simple code

That I am trying to compile for arduino microcontroller and without using avr headers. I just defined all macros in my source program file

but my gcc-avr says

led.c:15:8: error: lvalue required as left operand of assignment
   DDRB |= 0B100000; // PORTB5 1010
        ^

Now I can expect this error on some cpu that io area is not virtual memory space of this process but I am running my code on mocrocontroller that must have execution bit. how to get rid of this message and compile it and able to run on arduino

But the gcc-avr throws error that

#define F_CPU 16000000
#define BLINK_DELAY_MS 5000

#include <util/delay.h>

#define __SFR_OFFSET 0x20
#define _SFR_IO8(io_addr) ((io_addr)   __SFR_OFFSET)
#define DDRB    _SFR_IO8(0x04)
#define PORTB   _SFR_IO8(0x05)
int main (void)
{
  // Arduino digital pin 13 (pin 5 of PORTB) for output
  DDRB |= 0B100000; // PORTB5 1010
  
  while(1) {
    // turn LED on
    PORTB |= 0B100000; // PORTB5
   // _delay_ms(BLINK_DELAY_MS);
   int x=0;
   
    while(x<25)
    {
        x  ;
    }
    x=0;
    // turn LED off
    PORTB &= ~ 0B100000; // PORTB5
    //hello
    while(x<25)
    {
        x  ;
    }
    //_delay_ms(BLINK_DELAY_MS);
  }
}

CodePudding user response：

The problems are the macros, you are defining the register as an integer, not as an address to an integer.

DDRB expands to 0x04 0x20 so you end up with code like (0x04 0x20) |= 0B100000;. You should be able to fix this with a cast and then de-reference:

#define _SFR_IO8(io_addr) ( *(volatile uint8_t*) ((io_addr)   __SFR_OFFSET) )

For details see How to access a hardware register from firmware?

Please also note that macros starting with double underscore __ are reserved for the compiler, so we should never use that or we might end up with naming collisions.