Use case for the digital filter on an input pin

[durga_choudhury]

What is the intended use case for the digital filter on the I/O pins of the S32K1xx MCUs? It can delay the input for up to 31 clock cycles, but that is too small to be a debouncer for a push button (with the clock running from any source except for the 32kHz source), so it seems an external schmitt trigger or a software debouncer is needed for that. Is my understanding correct?

Also, on an unrelated note, when I access the NXP forums all the titles are in some Asian language; only the user generated code is in English (I am accessing this from the United States). This makes it cumbersome to use the site. I use Chrome running on Windows 11, but I have noticed the same behavior with Internet explorer as well.

[Senlent · Accepted solution]

Hi@durga_choudhury

yes, your understanding is correct.

The digital filter can delay input transitions by up to 31 clock cycles, which is useful for:

• Filtering out short glitches or noise on digital inputs (e.g., from EMI or bouncing signals in high-speed environments).
• Ensuring signal stability before triggering interrupts or logic transitions.

This is especially helpful for high-frequency signals or noisy environments, where short spikes could cause false triggering.

Use the digital filter for high-speed signal cleanup, like encoder inputs or external interrupts from fast peripherals.
For push buttons, rely on:

1. Software debouncing (e.g., wait for stable state for 5–20 ms).
2. Or external debounce circuits if hardware reliability is critical.

The language of the webpage can be changed after logging in. This should be related to your IP location, but I am not sure about the details.