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Embedded and Microcontrollers
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Embedded and Microcontrollers
Embedded Forum OO Digital Pin class: single class or separate in and out classes
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Related

OO Digital Pin class: single class or separate in and out classes

Jan Cumps
Jan Cumps over 2 years ago

I'm experimenting with light-weight C++ for microcontrollers. Looking for your opinion for class(es) that represent GPIO pin behaviour

An output pin can

  • accept a value and set it
  • return the value it is set to
  • maybe go high-z

An input can:

  • return the value at its input

I may represent this

  • very simple as a single class.
    Getting the value would perform the "return" action above. The class would decide if it returns output state or input state internally
    Setting would only succeed if the pin is an output pin, else either throw an exception or silently ignore.
    Switching between the two would be simple
  • as separate classes
    out type pin would set the output as indicated, and return the output state if asked
    in type pin would return the value at its input. It would not provide setters.
    Switching between two modes would mean discarding the original object and creating one of the other kind.
    (should both classes inherit from a common parent that defines the actual pin?)

How would you solve this, as OO designer / abstractor that loves simplicity?

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Top Replies

  • shabaz
    shabaz over 2 years ago in reply to michaelkellett +3
    The compiler was way better than I thought... I gave it a shot with the GNU compiler for ARM, using the Pi Pico SDK. I created a simple class: Then that class is used in the main() function. The…
  • ggabe
    ggabe over 2 years ago +2
    Take a look at WiringPi, as an example how the single class API can be structured: http://wiringpi.com/reference/ I like how it can abstract MCU GPIO and IO expanders under the same API. if you need…
  • Andrew J
    Andrew J over 2 years ago +2
    On the basis of your points above, what you are essentially describing is a variable: you can set a value and you can read a value. I don't think that would benefit from being encapsulated by a class and…
Parents
  • shabaz
    shabaz over 2 years ago

    Single class : ) Also it makes it easier to configure up loads of GPIO from an array etc. I would prefer it instead of DigitalOut and DigitalIn style. Usually it's very clear from the object name whether it is an input or output anyway (e.g. LED, Button). Input or output mode becomes only an incidental footnote kind of thing with single class approach, pushing more complexity into the class. I don't know if this is good or bad from software purist point of view!

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  • shabaz
    shabaz over 2 years ago

    Single class : ) Also it makes it easier to configure up loads of GPIO from an array etc. I would prefer it instead of DigitalOut and DigitalIn style. Usually it's very clear from the object name whether it is an input or output anyway (e.g. LED, Button). Input or output mode becomes only an incidental footnote kind of thing with single class approach, pushing more complexity into the class. I don't know if this is good or bad from software purist point of view!

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