Rising or falling edge.....

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Which would you use for pulse detection/counting?

 

[MooseFET]

Which would you use for pulse detection/counting?

It depends on a lot. In at least one case, I used both edges.

 

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It depends on a lot. In at least one case, I used both edges.

Assume noise is already filtered and you're just counting pulses with
a MCU where just changing a bit or two determines detection on rising
or falling.

 

[neon]

DEFENETLY RISE TIME if it is active fall time is usualy passive and therefore longer in time.

 

[TTman]

Which would you use for pulse detection/counting?

both for detecting, neg for counting.In a micro, you would use (preferably)
interrupts.

 

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both for detecting, neg for counting

So if noise is out of the picture and you have control over and set
the inactive steady-state of the pulse source to Lo, then it's only a
falling edge ISR that one needs to concentrate on?

 

[Rich Webb]

Always count rising edges. That way, if the universe comes to an end
in the middle of a pulse, you won't miss it.

Ding ding ding ding ding ... We have a winner!

 

[TTman]

Ding ding ding ding ding ... We have a winner!

Ha ha, if everything goes belly up, who cares if a pulse is missed, unless
you're counting gold bars
Happy Xmas you lot .

 

[Jamie]

Always count rising edges. That way, if the universe comes to an end
in the middle of a pulse, you won't miss it.

John

Hmm, sounds good for ECL, but how about CCL ?

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[Jamie]

Which would you use for pulse detection/counting?

Depends on the device that is doing the pulsing?

It's logical to use the level the device generates
when its TRUE/ON

For some, the raising edge how ever, this leads to
problems where the devices must insure it does not over
drive the unit that is receiving the pulse.

If you use an open collector type device for example, you
can then have the monitoring device use it's own pull up or
what ever voltage it requires and the pulsing device won't
care until you breach it's limits of course.

So, with that, I would say a falling edge using an open collector
pulser would be the ticket. And even if a totem pole/Line driver
output device was connected for some reason, it could thus use the
receiver device supply voltage to insure it does not get over driven.
And with that, you still can use falling edge..

In the case of a pulsing device that has NOT outputs with
open-collector, you then are faced with PNP outputs on the NOT's in
many cases and NPN on the non-NOT's
NOT's are high side, others are low side open-collector.
In the case of the NOT's, you would have to supply a pull down
R. unless you design your receiver device to work with NOT/PNP sensors.
etc..



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[Jasen Betts]

both for detecting, neg for counting.In a micro, you would use (preferably)
interrupts.

In an MCU you would use a hardware counter and interrupts only to
handle counter overflows

 

[Jasen Betts]

Depends on the device that is doing the pulsing?

It's logical to use the level the device generates
when its TRUE/ON

it depends if you're more interested in the beginning of the
event or the completion of the event.