Cypress FX2 bandwidth problem

Just to add small clarification -

What happens is that output FIFO on FX2 is not emptied on time by PC host (using USB BULK IN transfers) - this results that internal FX2 FIFO gets full for significant amount of time and we are currently not able to compensate this using small FIFO implemented in FPGA.

As the bandwidth we are using is only a fraction of bandwidth provided by USB 2.0, I'm suspicious about driver performance.

Damir

The USRP/GnuRadio people have equivalent hardware running reliably at 33 Mbyte/second, at least for most modern motherboards. Not sure about the Windows part, though, and certainly not with CyAPI & CyUSB. Check it out -- there is some trickery involved on all three fronts: FPGA programming, FX2 programming, and host programming.

- Larry

Damir,

I'm more of a hardware type than software, but I believe you're look> Just to add small clarification -

FPGA.

experience

the

is

it?

Hello,

I think your problem is a combination of the PC OS (Windows ?) and bulk transfer mode. On a system I designed using the Cypress FX and USB1.1 we were able to get average data rates up to 800k bytes/s (yes bytes/s) but needed a 40 kbyte buffer to cope with 'stalls'. Interestingly that's about the same as the 50mS you are seeing. If you don't write your driver properly you can make it a lot worse but we never got it much better.

Michael Kellett

snip snip

We needed 4 MBytes/sec Out (the OP was In) and saw that XP could disappear for several seconds (doing its own upgrade) so we have 16 MByte FIFO beyond the FX2.

We also had problems with overlapped IO which we wanted to use to have 20 MBytes of output queued. Output seemed to be re-ordered.

Cypress said their later driver is better. It implements IOCTL_ADAPT_SEND_NON_EP0_DIRECT (instead of IOCTL_ADAPT_SEND_NON_EP0_TRANSFER which requires the SINGLE_TRANSFER to preced the data in memory). However, I am not sure it really helped and so did not test it.

We did find technical support at

HTH Bill

As Gabor pointed out, bulk transfers are not the right ones for streaming data. On the one hand you get reliability due to the CRC checks and retries, on the other hand bulk transfers have no bandwidth reservation.

BUT:

If you have luck, it is only your FX2 driver. I don't know what driver you are using, but when doing only synchronous IO, your problem is much more likely to appear (well, almost guaranteed to appear...).

Windows and Linux can do pipelining of transfers, but it involves asynchronous driver calls and brings up tons of potential race conditions, which most lazy driver writers want to avoid. If you use Overlapped IO (Windows terminology) or Bulk Queuing (Linux), it should be possible to get a steady bulk transfer, as the host controller has always enough transfer descriptors to run.

As mentioned, we are using standar Cypress FX2 drivers and CyUSB and CyAPI.

Damir

You can also try to increase priority of your PC application. We had the similar problem and fortunately we could rise the priority up to Realtime, as the data arrived in bursts, so we didn't kill the rest of the system...

- Dejan

P.S. mozete me dobiti na donju adresu (jasno je sto treba maknuti), ako je potrebno...

snipped-for-privacy@dilogic.removeme.hr

damir escreveu:

I use the SX2 and could get around 25Mbit/s of sustained transfer in bulk mode, but remember that bulk transfers have absolutely no time guaranty. Even interrupt and isochronous that should have timeliness have a disclaimer in the USB specification that real timeliness is dependant upon SO. Windows and Linux can take a very long time without giving the processor to any specific task. I did no test at all regarding latency in this case. Depending on how critical is the data, you may need over 1s of buffering. Using drivers in windows i've seen sub-ms response times, but there's no way to be sure it will allways be so. I think the Cypress driver is quite slow also. In the test I achieved 25mBit/s the FPGA driving the SX2 could deliver over 120Mbit/s to the SX2, which sould be capable of even more....

Ricardo

Is there any alternative to Cypress driver available in the source, or I'll have to go and write driver (WinXP) by myself :(((( I've done some windows drivers several years ago and I don't like it at all.

Damir

damir escreveu:

Talking to the software guy here, USB drivers are the most documented one in DDK's. But, as the Cypress drivers achieves what we need right now, we're no looking anywhere else now.

Ricardo

Hi We are using Cypress FX2 in our project and we have our own windows(xp &

we have an FPGA interface which pumps data to FX2 fifo, and we are using Bulk data transfer.

rgds bp

"bp" schrieb im Newsbeitrag news: snipped-for-privacy@webx.sUNCHnE...

With the Cesys Spartan3e-500 board we sustained 35MBYTE/second

Antti

For how long period of time and which driver did you use?

Damir

"damir" schrieb im Newsbeitrag news:dojl4n$7bo$ snipped-for-privacy@ss405.t-com.hr...

I used the 'cesys API' what they supplied.

the bandwith was seen overage 35MB over pretty long time, but I did not do any timeconsuming tasks and there was no other devices on the usb bus either

Antti

Ok, we are running DSP intensive application on the PC which generates severe load which is probably the reason why data is lost.

Damir