My feeling on this that there is questionable value in learning a large
dictionary of symbols versus learning the meaning of each bit. So, why not
use for example BIT2 for PA2 and PB2 etc.
On Jan 24, 2014 9:49 PM, "Chuck McManis" <[email protected]> wrote:
> One of the things I did to make writing ARM code simpler was to define an
> enum called GPIO_PORT_PIN with the values PA0 .. PI15. These have the
> values 0 .. 143.
>
> Because of their numerical relation, you can do some math on them, like so
>
> GPIO_BIT_NUMBER(PB6) == (PB6 % 16)
>
> I exploit this in other ways too, which you can see in my library (cpa)
> which is hosted here: https://github.com/ChuckM/libcpa
>
> In particular, the libopencm3 interface to toggle a bit can be written:
>
> gpio_toggle(gpio_base(PB5), gpio_bit(PB5))
>
> or as I do in my #define, you can rewrite this that simply toggle(PB5);
>
> Now I'm not a huge fan of massive syntactic sugar, this is part of what
> makes the "standard peripheral library" from ST.M so distasteful. But this
> change to being able to 'name' GPIO pins has come in handy.
>
> Things you can't do of course, you can't say toggle(PB5 | PB6); (or even
> more creatively toggle(PB5 | PC2); Not sure if that is a problem or not for
> some.
>
> I also found when doing my SPI work that since you may have pins all over
> the map for an SPI port or a USART you can "safely" enable clocks or
> alternate functions for each pin, but that is slightly slower more verbose
> than setting groups of pins.
>
> I'm looking for feedback on whether or not that is a useful abstraction or
> not.
>
> --Chuck
>
>
>
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