Question regarding fast pins

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Posts: 69
Joined: 21 Sep 2016 08:53

Question regarding fast pins

Post by anom3 »

I have set up a nice little working FLiRS based wallswitch using a Z-Uno. My code is available at

I have a question regarding fast pins:

1) I tried setting up pins 17-20 as fast pins. I could only get 17 to respond correctly. Is it possible to only have 1 fast pin at a time?

2) Is there a point of using fast pins on a wallswitch? I am assuming the loop cycles at least a few times even though wallswitch clicks are fairly quick, but maybe the 'bring up' time for a fast pin is longer then any benefit you get from them?

3) Can INPUT_PULLUP pins be fast pins?
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Joined: 26 Jan 2011 19:36

Re: Question regarding fast pins

Post by PoltoS »

1) You can have many fast pins.
2) No need to use fast pins in your case IMHO. Fast pins is just a way to make digitalWrite work faster using indirect addressing (very specific for 8051 CPU).
3) Yes. Fast pins is just a trick to inform the compiler to make better and faster code due to the absense of real indirect addressing for SFR in 8051.
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