Using an external trigger with Digital Discovery Pattern Generator

[k_b]

Hi. I want to use the Digital Discovery Pattern Generator to run a pattern triggered by a signal coming from my system. On the Waveforms GUI it doesn't appear that there's an option to select a DIO to bring the external trigger in or any way to configure it. Am I missing something?

Regards,

Kevin

 

[attila]

Hi @k_b

Digital Discovery has no dedicated trigger IO but any DIO or DIN can be used to cross trigger the Pattern Generator by selecting Logic Detector as trigger source.

[k_b]

Hi Attila,

Thank you for the response! I'm getting it to trigger now by using the logic detector as you said. But I'm finding that it will trigger on any edge of the chosen trigger signal, even if I've got everything setup for rising edge trigger. You can see here that it's setup for rising edge trigger on DIO29 but it's triggering on the falling edge. I change it to falling edge, any edge, rising edge and it always just disregards the setting and triggers on the first edge it sees. Do you have any idea what could be happening here?

[attila]

Hi @k_b

It is probably trigger on signal ringing, glitch on the falling edge.
Zoom in, increase the sample rate to have a better view.

[k_b]

Hi Attila,

Thanks for the response. It actually wasn't ringing or glitch. It turns out the edge was too slow. Do you know what the slowest rise/fall time is that this can handle for a trigger?

 

[attila]

Hi @k_b

To prevent edge trigger on glitch, the timeout trigger can be used:

[k_b]

Hi Attila,

It wasn't triggering on a glitch. It was triggering because the edge being provided had too slow of a rise time. What is the maximum rise/fall time that this can handle for a trigger?

 

[attila]

Hi @k_b

Slow transitions plus noise can can cause ringing-like false triggers. In the following picture a glitch trigger was used to catch such an event.
To reduce the chance of this use faster slew signal, and shielded or twisted signal wire with ground to reduce noise, or use pulse timeout trigger.
Currently the max edge is 1.25ns (due to 800MHz internal sampling) but I'll try to add glitch filter adapting sample rate in the next sw version.

[attila]

Hi @k_b

The latest version adds glitch filter for edge trigger with Digital Discovery: