Re: [avr-gcc-list] direct port access

[Volkmar Dierkes]

On Wed, 22 Jan 2003 14:58:38 -0700, E. Weddington wrote:

> On 22 Jan 2003 at 10:57, Marlin Unruh wrote:
>
>> I have some code that was working with the old style io.h. I am tring
>> to get the code working with the new style (#define
>> PORTD        _SFR_IO8(0x12))
>>
>> void Pdu1_In_Port(unsigned char* buff)
>> {
>>  unsigned char tmp;
>>  unsigned char * const iobase = (unsigned char*)0x20;
>>  unsigned char address;
>>  address = buff[10]; // get address of port
>>  if(address < SPL) { // exclude SREG and Stack Pointer Registers
>>   tmp = *(iobase + address); // read i/o space address
>>   tmp &= ~buff[6]; // inverted mask low byte AND
>>   tmp |= (buff[6] & buff[8]); // get data low byte
>>   *(iobase + address) = tmp; // write i/o space
>>  }
>> } // end of Pdu1_In_Port
>>
> <snip>
>
> Well you didn't say what the above code is actually doing in it's 
> error.
>
> But this could be a problem:
>
> if(address < SPL) { // exclude SREG and Stack Pointer Registers
>
> SPL is defined as a _SFR_IO8(..., which is not going to be the same 
> thing as what your address is declared as. Rewrite as:
>
> if(address < &(SPL))
>
> That way you're comparing a memory address to a memory address.

Eric,

I think he want to use adress as a pointer to a io register. But 
adress is now a pointer to memory. I didn't know how to declare 
adress as an pointer to IO, but I think that leads to the solution.

Volkmar
avr-gcc-list at http://avr1.org