What's a good way to be hardware independent?

Projects Programming
12

I was thinking about it yesterday and here is something that is quite close to the arduino approach, but doesn't suffer its performance penalty:

#define VAR_SET(var, id, pin)	var ## id |= _BV(pin)
#define VAR_CLR(var, id, pin)	var ## id &=~_BV(pin)
#define VAR_TOG(var, id, pin)	var ## id ^= _BV(pin)
#define VAR_GET(var, id, pin)	((var ## id) & _BV(pin))

#define pinOutput(pin)			VAR_SET(DDR, pin)
#define pinInput(pin)			VAR_CLR(DDR, pin)

#define pinSet(pin)				VAR_SET(PORT, pin)
#define pinClr(pin)				VAR_CLR(PORT, pin)
#define pinTog(pin)				VAR_TOG(PORT, pin)

You would define a pin, like

#define HC595_SCK B, 0 //hc595 on portb.0

and use it later:

  pinOutput(HC595_SCK); //hc595_sck as output
  ...
  do {
    pinClr(HC595_SCK); //clear hc595_sck
    ...
    pinSet(HC595_SCK); //set hc595_sck
  }

If you have reassigned HC595_SCK to PORTC.6, you just need to redefine it:

#define HC595_SCK C, 6 //sck now on portc.6

and recompile.

Something like this is very portable as it does not rely on bit fields, and present no performance penalty or re-entrance issues.