Simultaneous sampling and reading via SCPI & LabVIEW

[tech62]

Hello all,
I am using LabVIEW & SCPI to write and read from the dual fast analog io.
Writing is fine.
I wish to capture on both analog in channels simultaneously and then recover the data via SCPI.
When I do this, with the same signal into each input for a test, I find the READ data between each channel is not aligned...and there is what seems to be a constant delay between the data in each channel.

Capture.PNG

I am acquiring with Decimation set to 8192.

To try and figure this out I have a few questions:
Q: Does the RP capture both channels simultaneously ?
Q: If so, can pointers be used to retrieve the data from each channel so it is aligned ? or some other method...otherwise my program cannot figure out how to align the signals.
Q:Can both channel buffers be read at the same time ? maybe this will help ?

I get the impression there is a lot more control available by using C APIs, but for now I am trying to get results with the LabVIEW SCPI features.

Any hints much appreciated.
tech1962

[redpitaya]

Hi,

here are the combined answers to your questions from the forum and emails to the support:

• Q: Does the RP capture both channels simultaneously ?
  Yes both channels are captured simultaneously
• Q: If so, can pointers be used to retrieve the data from each channel so it is aligned ? or some other method...otherwise my program cannot figure out how to align the signals.
  Yes you can use data pointers for each buffer. See the Data pointers paragraph for more details.
• Q:Can both channel buffers be read at the same time ? maybe this will help ?
  No, they can not be read at the same time.
• Q: can we have the same decimation on the ADC and DAC channels?
  Arbitrary values for both ADC and DAC channels will be possible with the next SCPI that we are currently developing. That should be completed at the end of September.

kind regards Red Pitaya team

[tech62]

Thanks for the reply:
My comments below also >>>

Q: Does the RP capture both channels simultaneously ?
Yes both channels are captured simultaneously
>>>I have found that setting a trigger creates aligned data in both channels.

Q: If so, can pointers be used to retrieve the data from each channel so it is aligned ? or some other method...otherwise my program cannot figure out how to align the signals.
Yes you can use data pointers for each buffer. See the Data pointers paragraph for more details.
>>>Yes, using WPOS and TPOS gives some insight.

Q:Can both channel buffers be read at the same time ? maybe this will help ?
No, they can not be read at the same time.
>>>No problem. They can be read sequentially via SCPI.

Q: can we have the same decimation on the ADC and DAC channels?
Arbitrary values for both ADC and DAC channels will be possible with the next SCPI that we are currently developing. That should be completed at the end of September.
>>>That will be very helpful..so that tx and rx rates can be set the same even via SCPI...and having more options will be even better.
Looking forward to the update.