Pulse trigger for oscilloscope/acquire

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Hans Pirch
Posts: 1
Joined: Tue Oct 07, 2014 12:34 pm

Pulse trigger for oscilloscope/acquire

Post by Hans Pirch » Tue Oct 07, 2014 12:58 pm

Hi all,

I just got my redpitaya recently and it is a great device.
The one thing I am missing for it to fulfill everything I need is a pulse trigger option for the scope/acquire tool.
I started to look at the code, but it may take me quite long to implement this given that I am a HW engineer and all programming I am doing is in Matlab or small FW for micro controllers.
So I thought I'll ask if anybody is working on such an option or planning to extend the current functionality in the future.

If not - could maybe someone point me in the right direction?

Thanks a lot for the great product!
Hans

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Pulse trigger for oscilloscope/acquire

Post by Nils Roos » Tue Oct 07, 2014 1:36 pm

My current project on the RedPitaya is the continuous acquisition / ADC-to-DDR topic, where I expect to have something usable before christmas.
After that, I plan to enhance the trigger capabilities, but that will have to wait until next year.

I can give you some pointers on how to add a pulse trigger mode:
The FPGA scope block already generates edge trigger signals from the input data on the fly - look for

Code: Select all

reg               adc_trig_ap      ;
reg               adc_trig_an      ;
reg               adc_trig_bp      ;
reg               adc_trig_bn      ;
in /FPGA/release1/fpga/code/rtl/red_pitaya_scope.v
These signals go active whenever a corresponding edge is detected in the input stream. You could use them to control a small state machine that counts the time between two edges and derive a new trigger signal from that.
Add configuration registers (eg. pulse-width), a new trigger-mode setting for your new trigger, and adapt the scope, etc. applications to use your new trigger and voila.

Deriving the trigger outside of the FPGA is also possible as long as you can read the ADC data faster than they are acquired (break-even for that occurs at 64 times decimation, apparently).
You would need to read the datastream and analyse it for interesting features in software, then.

brian
Posts: 4
Joined: Wed Apr 29, 2015 10:07 am

Re: Pulse trigger for oscilloscope/acquire

Post by brian » Wed Apr 29, 2015 10:18 am

Hi. New RP user here too.

I noticed that the included "acquire" functionality does almost all I need as well (though I probably need a small shell script). However, at the moment it only can use "auto" trigger, whereas I need to be able to set the trigger.

In particular, I need to trigger sampling at a rising edge passing a given voltage level (e.g. 1V). It would be wonderful if there was a small command-line program available that lets us set the trigger details.

In the beginning, I thought it would be possible to access the device from Python (through api's), but these appear to be not yet in place. I'm not bad at programming in Python, but I'm ashamed to say I am not good at anything else.

Anyway, would the hardware supports this type of trigger adjustment? Would a command-line trigger setting function be hard to write?

Cheers,


Brian.

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