SDK • Re: Handling (multiple) input pins in a PIO program and making sense of their data

I don't think I'll run it that fast: I think I'll end up using too much instructions waiting as I need to wait 12us before pulling ACK low (my sideset pin).

You could of course use a loop to create the 12us delay, but yes if you actually want a fixed 12us delay then a slower clock could be sensible.

Note that if you are using 1 bit of side-set then you've only got 0-15 for the delay field (1-16 including the basic 1 cycle for the instruction itself), though typically when you want a delay like this you can find two or three instructions to spread the delay over.

However, for this application I'm not sure I would use side-set: using SET seems perhaps more convenient. Either way, if this is open-collector then it needs to be SETing or side-setting the PINDIRS rather than the pin.

First, really make sure you understand the protocol inside and out.
Then, before touching C or Python, sketch out your plan using pseudo code in your normal spoken language
(like plain English). Just outline the steps.

While that's sensible generic advice, there's one specific aspect that applies when writing PIO programs: the assignment of signals to pins is critical. Certainly you should write your whole PIO program before wiring up a PCB, as the ordering of signals onto GPIO numbers often constrains what the program can do: when seeking best performance or minimal PIO instructions to make it fit, you often find you want the signals wired up in a different order to what you first tried.

Statistics: Posted by arg001 — Sat Apr 12, 2025 1:09 pm

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