Re: [avr-gcc-list] Question about gcc preprocessing and port/pin assignments

[James Washer]

Very nice. Thanks

 -jim
On Mon, 6 Dec 2004 15:19:18 -0800
"Dave Hylands" <address@hidden> wrote:

> Hi James,
> 
> Just a word of caution.
> 
> Using 
> 
>     #define   SETPIN(pindef)  PINDEF_PORT(pindef) |=
> PINDEF_PIN(pindef)
> 
> and passing in DATA1 which is defined as a comma separated list, isn't a
> portable construct. Gcc happens to compile it (I tried 3.3.3 and 3.4.1
> which both worked), however other compilers will probably complain. It
> would be better to rework them slightly to look like this (I also
> renamed a couple of things):
> 
> //Example defines
> #define       DATA1         D, 7
> #define       DATA2         C, 3
> #define       DATA3         B, 3
> 
> //Code to manipulate PORTx, PINx, and DDRx using definitions like those
> above
> #define       PORT(port,pin)     (PORT##port)
> #define       DDR(port,pin)    (DDR##port)
> #define       PIN(port,pin)      (PIN##port)
> #define       PIN_MASK(port,pin) (1<<(pin))
> 
> //Set a pin
> #define       SETPIN(port,pin)        PORT(port,pin) |= PIN_MASK(port,pin)
> 
> //Clear a pin
> #define       CLRPIN(port,pin)        PORT(port,pin) &= ~PIN_MASK(port,pin)
> 
> //Set a IO to output
> #define       SET_DDR_OUT(port,pin)   DDR(port,pin) |= PIN_MASK(port,pin)
> 
> //Set a IO to input
> #define       SET_DDR_IN(port,pin)    DDR(port,pin) &= ~PIN_MASK(port,pin)
> 
> //Read the value of a pin
> #define GETPIN(port,pin)  PIN(port,pin) & PIN_MASK(port,pin)
> 
> - With these redefinitions PORT, DDR, and PIN reflect the PORTx, DDRx,
> and PINx registers.
> - PIN_MASK is more intuitive to me, and allows PIN to be used as the
> register.
> 
> DDR_OUT and DDR_IN don't really have a verb, so adding the word SET
> makes them more like SETPIN/CLRPIN. You might also want to consider:
> 
>     SETDIR_IN, SETDIR_OUT
> 
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/ 
> 
>