How to design a very flexible automotive grade digital input

So I'm designing a module that reads and then sends analog and digital inputs over CAN bus.

I'm having trouble deciding how to tackle the digital input design.

In motorsport electronics these type of inputs normally have quite a bit of flexibility.

Some engine management systems incorporate all possible digital functions in every pin for maximum flexibility.

Everything from simple button switch inputs (active ground or active high mind you), to frequency measuring capability for speed inputs with waveform capture capability (positive and negative voltages).

The speed inputs will support both hall effect and inductive (variable reluctance) speed sensors which can sweep positive and negative sometimes over 100v..

Since they also have the ability to adjust voltage thresholds and hysteresis in software They can support almost any digital signal, with diagnostics for each input for detecting threshold and hysteresis noise and rejected pulses..

How can they accept so many different types of signals on any pin (some ecu's have up to 12 of these pins)? are they using high speed analog inputs and analyzing the signals and emulating a digital signal in software?
Are they using tons of digitals potentiometers and adjusting comparators? In the past I would design a different circuit for each of these features and give that pin a specific functionality.

Id just like to see how other people would approach this; I might be over thinking it. which I do often. I've yet to go very deep into digital input circuitry so far..

Thanks,

Xavier M
 
Since they also have the ability to adjust voltage thresholds and hysteresis in software They can support almost any digital signal, with diagnostics for each input for detecting threshold and hysteresis noise and rejected pulses..
That would be configurable comparator on the input I reckon, plus some clocked-counters to determine runt pulses from longer ones. Basically they will have implemented the functionality needed for the job on those pads. Automotive environments are very harsh, I suspect they also specify external RC or RL filtering as well.

Most microcontrollers have some noise pulse filtering, particularly when a pin is used as an interrupt source, and various amounts of configuration for the pads, but less comprehensive.

BTW I suspect most of the signals they handle are very slow (in electronics terms) - so quite a lot can be done in software, just not the levels and hysteresis and protection.
 
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