Re: [avr-gcc-list] Bit-wise structure and unions

[Joerg Wunsch]

Keith Gudger <address@hidden> wrote:

> But I would rather not have the union.  Is there any other way
> around this?  Thanks.

While I agree with David and Eric that your non-union version prevents
you from manipulating multiple bits at once, the following will work:

struct port_reg {
        unsigned char bit0: 1;
        unsigned char bit1: 1;
        unsigned char bit2: 1;
        unsigned char bit3: 1;
        unsigned char bit4: 1;
        unsigned char bit5: 1;
        unsigned char bit6: 1;
        unsigned char bit7: 1;
};

#define PORTB_BITS (*((volatile struct port_reg *)0x37))

void
foo(void)
{
        PORTB_BITS.bit0 = 1;
        PORTB_BITS.bit1 = 0;
}

You forgot the "volatile" anyway.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)