I have to admit to searching out and doing cut and paste every time I
need to insert an action on a peripheral, so anything that is more
intuitive would be helpful. It needn't displace the API as it is now for
those who want to do kinky things like toggling multiple bits at once.
It's debatable whether it should be an integral part of the existing API
or as part of a wrapper.
Ken
On 25/01/14 08:19, Chuck McManis 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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