Driving pattern generator with offline computed pattern

[Mka]

Hi,

I'm confused by the descriptions of the pattern generator implemented in Digital Discovery and/or AD2.

So a few questions:

1. Can I load an offline computed arbitray pattern (1 bit/cycle/pin, cycle time ~10ns)  which is then repeated forever on the digtal output pins in circles?
2. What's the maximum pattern size? Is it 32k samples?
3. Any hack to store the pattern into DDR3? The DRAM seems to have 2Gb so that a total pattern length of ~128M Samples should be possible. There should also be a ton of BW avaliable on the DDR3 to feed 16 bits@100MHz

Best regards,

  Michael

[attila]

Hi @JoeBeef

The Pattern Custom mode uses the limited FGPA BRAM (~512kbit) to store the samples. This has random access, so each signal can run independently (frequency, phase).
The Logic Analyzer Record (capture) and Play mode on Digital Discovery uses the large DDRAM (2Gbit). Here random access would highly limit the sample rate.

[attila]

Hi @JoeBeef

The latest beta version changes the Logic Analyzer import samples to 256M.
You also have the Import Binary file, which is faster than parsing huge text files, and you can add tab from Script.
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

 

[JoeBeef]

Hi @Attila,

Thank you for looking into this issue, will be waiting for the software update.

 

Regards,

[attila]

Hi @JoeBeef

After repeating the test I notice the import is indeed limited to 10M....
In the earlier test, quickly looking at the values and expecting 11M... I have confused the frequency with number of samples with 
I will push a software update next week.

 

[JoeBeef]

Hi @Attila

Thanks for the info, is there an updated documentation available describing the new feature?

Have you tried a single tab with 11M samples or it was split over several tabs?

 

Regards,

[attila]

Hi @JoeBeef

In the latest beta version you can use:
print(Logic.Time.Samples.real)
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

I was not able to reproduce the issue. I tried importing large files 11M and more, more than 50 tabs...

 

[JoeBeef]

Hi @Attila,

Yes I do have plenty of disk space. I tried splitting my pattern file(original 11M samples) in two files (9.0M and 2M samples) and did two separate imports and that worked fine showing me the actual samples, but it does not explained why it only showed 10M.

 

Regards,

[attila]

Hi @JoeBeef

The sample limitation in the application is 256M
The larger tabs/buffers, above 100k, are stored in on the disk. 10M samples are stored as 40MB.
Do you have sufficient disk space ?

Checking the number of samples requires copying the data to the Script which may be slow or run out of memory...
Logic.Tabs.value = 1 // or .text = "Tab 1" switch to first tab
print(Logic.Channels.DIN0.data.length) // see the data.length of any signal/bus/interpreter 
I will add to the next app version other way to check the number of samples.

[JoeBeef]

Hi @Attila,

Is there a sample size limitation per Tabs?.

I tried to import a file that have 11M  samples and at the end of the import the message is showing that I have 10M samples. All other imports that I have done are showing the correct number of samples.

Also, what would be the code to add to the script to display the number of samples in a tab?.

 

[JoeBeef]

Thanks

 

[attila]

Hi @JoeBeef

You can do a pretest to see if the tab with name exists:

const tabname = "Tab 1"
if(Logic.Tabs.preset.indexOf(tabname)<=0) throw "error" // 0 buffer, -1 not found
Logic.Play.Source.text = tabname

[JoeBeef]

Hi @Attila,

That is working great, I was able to generate a pattern with 5M of points.

Now, I am controlling the Logic analyzer through a script, is there a way to validate in the script that a tab name is valid before launching the play ?

 

Regards,

[JoeBeef]

Hi Attila,

Great, thanks for the excellent support.

 

Regards,

[attila]

Hi @JoeBeef

You can control the Play just like the Logic Analyzer Record.
Logic.Play.Source.text = "Tab 1"
Logic.run()
Logic.wait()

If you want to use it from SDK, custom application or script. Here you have an example:
 DigitalDiscovery_PlayRecord.py

[attila]

Hi @JoeBeef

I will look at this next week. I'm off work this week.

[JoeBeef]

Hi Attila,

Thanks for the info, one last question, is this option available through script yet ?

Regards,

[JoeBeef]

Hi,

Thanks for the answer, too bad that would have fixed the Pattern tool memory limitation.

Is there any plan in the future to use the loaded data as custom input for the Pattern tool ?

 

Regards

 

[attila]

Hi @JoeBeef

In this Play mode it is not supported to delay one signal from another.
Such you could do in external application and import the edited samples.

[JoeBeef]

Hi Attila,

Finally figured it out with your last post, I can load all my data fine.

One thing I am not sure about. I noticed that all signals are synchronized with the play rate. 

Like if I want my data to switch before my clock signal, I would delay the clock or generate a pulse later in the cycle.

Is it possible to add delay between signals like it can be done in the Patterns Tool ?

 

Regards,

[attila]

Hi @JoeBeef

The Play output is on DIO lines of the raw tab data.
Notice that you are generating on DIO lines are Recording on [DIN 0:23 DIO 24:31]

Here I have connected DIN 0:15 to DIO 24:39

 

This is what it Records:

[JoeBeef]

Hi Attila,

I got myself a DigitalDiscovery and got to the point were i loaded some data. I configure the Play mode to use the data loaded but when I hit Play nothing is coming out!

Can you shed some light on how the data flows in the DD when you hit Play, do I need to also configure the Pattern tool for this IO, if so is it as custom type ?

I am a little confuse as where to go from there.

Regards,

 

[attila]

Hi @JoeBeef

The "Play" mode is only available with Digital Discovery which has large DDRam.

[JoeBeef]

Hi,

Just noticed , your example is with a DDiscovery, is it also working with the Analog Discovery 2 ?

 

Regards,

[JoeBeef]

Hi Attila,

Thanks for the info.

I downloaded the latest Beta version of Waveforms (3.13.6 64-bit), but never was able to get the Play mode, it's not in any option even after I imported some data in csv format.

I am definitly missing something...but what?

Also, with the Pattern Generator we have the capabilities to move signal around by changing the phase and delays, are we loosing that flexibility with the proposed approach.

Please let me know what I am doing wrong.

Regards,

 

[attila]

Hi @JoeBeef

In the latest beta version you have Play option in Logic Analyzer:
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

1. Load data from file or Record and it to a "Tab".
2. Select 'Play' mode and configure it (rate, trigger...), optionally you can also Record while playing.