AVR sbi command - Error: number must be positive and less than 32

Question

I've spent a good while getting my AVR development system set up with the full GCC tool chain (everything is the most recent current stable version) and I have solved most issues with it but one.

This following code gives me an error which I just don't get. The AVR assembly manual states that the sbi instruction can accept 0-7 as a constant expression but it still errors out on me. Can anyone shed some light onto why it does this please?

  #ifndef __AVR_ATmega168__
      #define __AVR_ATmega168__
  #endif

  #include <avr/io.h>

      rjmp Init

  Init:

      ser r16
      out DDRB, r16
      out DDRD, r16

      clr r16

      out PORTB, r16
      out PORTD, r16

  Start:

      sbi PORTB, 0
      rjmp Start

The line in question is sbi PORTB, 0.

Compiled / assembled with:

avr-gcc ledon.S -mmcu=atmega168

Answer 1

I think it's complaining about PORTB rather than the bit number (0). How have you defined PORTB ? It needs to be in the range 0..31. You may need to subtract 32 from PORTB if your ports are defined in the range 32..63 ?

Answer 2

If you comment out the offending line and just compile the rest, you can take a look at the resulting object file with avr-objdump -D ledon.o.

That will show you that the value of PORTB is actually 0x25, and thus out of range for sbi like Paul suggested.

00000002 <Init>:
   2:   0f ef           ldi     r16, 0xFF       ; 255
   4:   04 bd           out     0x24, r16       ; 36
   6:   0a bd           out     0x2a, r16       ; 42
   8:   00 27           eor     r16, r16
   a:   05 bd           out     0x25, r16       ; 37
   c:   0b bd           out     0x2b, r16       ; 43