[Icc-avr] dumb pointer question

[John Woods]

Hi Paul,

You want to use the '*' in front oft he P_PORT when doing accesses so 
that bit operators work on the port and not the pointer itself. For example:

*P_PORT &= ~w_pin;

Paul Mateer wrote:
> Hello All.....
> Please tell me what I'm doing wrong here:
>
> void Process_Cmd(void)
> {
>   unsigned char *P_PORT;
>   int w_port, w_pin;
>  
>   w_port = WHICH_PORT & 0xF0;
>   w_pin = WHICH_PORT & 0x0F;
>  
>   if(w_port == 0x10) P_PORT = &PORTA;   // PORT A  
>   if(w_port == 0x20) P_PORT = &PORTB;   // PORT B
>   if(w_port == 0x30) P_PORT = &PORTC;   // PORT C
>   if(w_port == 0x40) P_PORT = &PORTD;   // PORT D
>   
>   if(w_pin != 8)
>    {
>      if(PORT_CMD == OFF) P_PORT &= ~w_pin;
>      if(PORT_CMD == ON) P_PORT |= w_pin;
>    }else
>      {
>        if(PORT_CMD == OFF) P_PORT = 0;
>        if(PORT_CMD == ON) P_PORT = 0xFF;                    
>      }    
> }
>
> //------------------------------------------------------------------------------------------------
>
> I always seem to stumble when it comes to pointers
> -- 
> Paul Mateer, AA9GG
> Elan Engineering Corp.
> www.elanengr.com <http://www.elanengr.com>
> ------------------------------------------------------------------------
>
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-- 
John Woods                      Phone: (780) 431 1843
Idea Technologies Inc.          Fax:   1 866 293 5883
6746 75 St.               	Email: john at idea-tech.com
Edmonton, Alberta,              Web:   www.idea-tech.com
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