Cy7C68013 USB RAW - Visa Read buffers

[jttull]

Hi

I'm using a CY7C68013A to stream ADC data to a PC. 

On the PC side I'm using a visa Driver (generated by the NI-VISA driver Wizard) and using USB RAW, I'm able to start transferring data to the PC.

Trying to speed up the streaming, I'm using 3 Visa reads in parallel (3 different while loops)) feeding the data to a queue, but it does not seems to have any impact (when compared to a single VISA read)

The ADC is generating about 8.6MBytes/Sec.

Any suggestion?

Thanks in advance

[Intaris]

Your read is a Control pipe, Bulk pipe or what?

[jttull]

Hi

I'm using Bulks..

(Code attached)

[Intaris]

can only suggest two things.

1) Try changing the IO to asynchronous (right-click the Read nodes and select Asynchronous mode)  I don't think this will help when dealing with a single device but it's easy to try.

2) Read less data at a time.  You might be running into memory allocation problems reading relatively large blocks at a time.  Try reducing the individual block size and see what happens.

Shane.

PS what speed ARE you getting?

PPS Try dequeuing your data to prevent memory allocation becoming a factor in your benchmark.

[jttull]

Thanks for the suggestions.

Changing the IO to asynchronous did not had any impact, and reading less data leads to more data holes.

(I’m probing the ADC with a scope to check for streaming “halts”)

I’m able to read at 8.6Mbytes/s (and even more) but I always get “gaps” that depending on the block size can reach 1ms.

The code I sent is only a fraction of the actual code. On the actual code I’m dequeuing the data on another while loop (for data storage, signal processing, etc)

BR

[Intaris]

Hmm, the request you send is to start the device streaming, right?  I presume there's zero buffering on your device?

I don't know if you can set up multiple Bulk reads in parallel.  I know it works for Interrupts (otherwise you can miss mouse events) but I've never tried it for Bulk.

Sorry, I'm at the end of my experience in these matters.

Shane.

[jttull]

Hello

Yes, I have implemented some vendor commands, and that one is to start streaming. 

Regarding your second question: I dont have any buffering/fifos between the ADC and the Cy7.

Thanks again