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what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Mon Jul 22, 2019 10:36 am
by HF_ATL
Does anybody know what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?
I don't see that information in BCM2837 datasheet...

Thank you and best regards

Re: what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Mon Jul 22, 2019 1:12 pm
by Heater
No idea. Almost certainly shorter than the shortest pulse you can generate. Given the clock rates it must be down to a nanosecond or 2.

I'm curious, what high speed thing to you want to get interrupts from?

Re: what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Mon Jul 22, 2019 1:33 pm
by jdb
In theory, a pulse wider than 3 system bus clocks will be detected (assume the bus clock is 250MHz), so pulses wider than 12ns should trigger an interrupt and latch the event detect register(s).

Driving these pulses reliably so you only get a single event is another matter - if the input voltage bounces around due to stray loop inductance then the event will be retriggered for as long as the ringing passes the pin's VIH/VIL.

Re: what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Tue Jul 23, 2019 8:54 am
by HF_ATL
Many thanks both for your replies.
Indeed I'm starting with python programming as well as in the raspberry pi and wondering about the shortest pulse width possible when searching for information about interrupts on the RPi.

Re: what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Tue Jul 23, 2019 9:10 am
by jamesh
HF_ATL wrote:
Tue Jul 23, 2019 8:54 am
Many thanks both for your replies.
Indeed I'm starting with python programming as well as in the raspberry pi and wondering about the shortest pulse width possible when searching for information about interrupts on the RPi.
Using Python means a lot of extra code between you and the hardware - you won't be able to get near the figures above with it.

Re: what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Tue Jul 23, 2019 9:13 am
by HF_ATL
So I must use C?

Re: what is the shortest pulse width that the Raspberry Pi 3 B GPIO interrupt pins can detect?

Posted: Tue Jul 23, 2019 9:41 am
by joan
We don't know what you want to do. You need to explain what you are trying to achieve.