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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