[c-prog] Re: Quadrature Rotary Encoder read

[John Matthews]

--- In c-prog@yahoogroups.com, Csaba Zvekan <czve...@...> wrote:
>
> Here is my little sub routine in C:
> 
> static void encoderRead(void)
> {
>       if (IOPIN &(1<<RENC1A)){  // true if button released (active low)
> Csaba

Hi Csaba - I'm interested in your definition of IOPIN. Is it memory mapped eg.

#define IOPIN (*(unsigned char *)0x1234)

Because in C it can help to use the volatile keyword to prevent the compiler 
optimising out successive reads of IOPIN, which it would otherwise assume to 
return the same value:

#define IOPIN (*(volatile unsigned char *)0x1234

John