I’m using ADP3450 to create a test bench for an analog pixel sensor in our lab. The pixels output at the same frequency as the input clock of the sensor, so each pixel lasts one clock period.
As we need to go fast to have a maximum images per seconds, we need high frequency (10 or 20 MHz are the working frequency of our sensor), and we want to have as little data as possible, to reduce the amount of data to transfer. So, we want to sample only 1 point per pixel, so we created another clock delayed from the sensor frame, to be sure to sample the correct value of each pixel (green one in the oscilloscope pictures below), with an external generator, and we set it to trigger 2.
So we used the "Sampling clock" function with the trigger 2 in the WaveForms Scope to test, and created signals representing the sensor frame with an external generator (yellow one on the pictrures).
The blue signal below represents a marker which allows the acquisition to start at the moment the frame begins, so we put it as the scope trigger (on trigger 1).
4MHz picture :
5MHz picture :
5MHz picture zoomed :
Unfortunately, we notice that with the sampling clock, we don't get all the points of the signal as desired from a certain frequency (in "Repeated" mode). Up to 4MHz everything is fine, but from 5MHz onwards we only get one sample in two, in an alternating way (samples 1-3-5, then 2-4-6, then 1-3-5, etc.).
Screenshot of the 4MHz output :
Screenshot of the 5MHz output (2 parts) :
By increasing the frequency, this phenomenon persists, or even increases (even fewer samples taken).
However, we do not observe any problem upstream (see the photos of the oscilloscope), or via WaveForms if we remove the sampling clock (we see the whole frame correctly, see the screenshot below).
Screenshot without the sampling clock :
We also tried with Analog Discovery 2, the same problem occurs from 6MHz. With other display modes (Screen, Shift, Record), we can observe the phenomenon, and we can observe it even at lower frequencies.
As we have only generated a few pixels that represent the beginning of the frame, this represents only a few samples, and we do not think that this is a buffer problem, but perhaps we are mistaken.
So I’m here to ask the question, do you think we have misconfigured or misunderstood the operation of the sampling clock or the triggers, or even the device itself? If yes, what do you advise us to try or modify? If not, do you know where the problem can come from?
I hope that my problem is clear, if you have any questions don't hesitate.
Thank you,
Manon.
Edited by ManonH I made a mistake by putting the wrong pictures in the post
Question
ManonH
Hi,
I’m using ADP3450 to create a test bench for an analog pixel sensor in our lab. The pixels output at the same frequency as the input clock of the sensor, so each pixel lasts one clock period.
As we need to go fast to have a maximum images per seconds, we need high frequency (10 or 20 MHz are the working frequency of our sensor), and we want to have as little data as possible, to reduce the amount of data to transfer. So, we want to sample only 1 point per pixel, so we created another clock delayed from the sensor frame, to be sure to sample the correct value of each pixel (green one in the oscilloscope pictures below), with an external generator, and we set it to trigger 2.
So we used the "Sampling clock" function with the trigger 2 in the WaveForms Scope to test, and created signals representing the sensor frame with an external generator (yellow one on the pictrures).
The blue signal below represents a marker which allows the acquisition to start at the moment the frame begins, so we put it as the scope trigger (on trigger 1).
4MHz picture :
5MHz picture :
5MHz picture zoomed :
Unfortunately, we notice that with the sampling clock, we don't get all the points of the signal as desired from a certain frequency (in "Repeated" mode). Up to 4MHz everything is fine, but from 5MHz onwards we only get one sample in two, in an alternating way (samples 1-3-5, then 2-4-6, then 1-3-5, etc.).
Screenshot of the 4MHz output :
Screenshot of the 5MHz output (2 parts) :
By increasing the frequency, this phenomenon persists, or even increases (even fewer samples taken).
However, we do not observe any problem upstream (see the photos of the oscilloscope), or via WaveForms if we remove the sampling clock (we see the whole frame correctly, see the screenshot below).
Screenshot without the sampling clock :
We also tried with Analog Discovery 2, the same problem occurs from 6MHz. With other display modes (Screen, Shift, Record), we can observe the phenomenon, and we can observe it even at lower frequencies.
As we have only generated a few pixels that represent the beginning of the frame, this represents only a few samples, and we do not think that this is a buffer problem, but perhaps we are mistaken.
So I’m here to ask the question, do you think we have misconfigured or misunderstood the operation of the sampling clock or the triggers, or even the device itself? If yes, what do you advise us to try or modify? If not, do you know where the problem can come from?
I hope that my problem is clear, if you have any questions don't hesitate.
Thank you,
Manon.
I made a mistake by putting the wrong pictures in the post
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