Blackfin TCP/IP transfer rates

[sesexton]

Hello All

     I have built an application on the Blackfin that reads out the value of the timers, and transfers that data over ethernet to a data collection host. It seems that the throughput of the Blackfin's TCP/IP subsystem is VERY slow. I am using the canned LabView TCP functions to transfer the timer data. It is taking about 15 seconds to transfer 3 seconds worth of data (32 bit word generated at 10KHz, or 320Kb/s data rate). Consequently I am losing data since the buffer is overflowing. The TCP Write vi seems to send whatever data it is presented in a single packet, so I have tried packing the data into larger groups, so I don't have to call the function as often. I have also flattened the data, to reduce the overall size. The speed is still way off the 10Mb/s ethernet rate. Is there a configuration setting I am missing, or is this normal?

Thank You

Sean Sexton

[NIJanell]

Hello Sean,

Are you using LabVIEW 8.2.1?  If so, there are some known issues that may explain the behavior you are seeing.  I have copied them below:

• Using instrumented debugging (TCP or serial) with a Blackfin application that has a loop with no waits might cause LabVIEW to fail to connect to the Blackfin application
• If you use TCP for debugging or the application uses TCP functions, you must wait at least two minutes after ending the debugging session before you can reconnect to the Blackfin target. As an alternative, you also can power cycle the target by unplugging and plugging the cable to the EZ-Kit
• You must disable data caching if you enable lwIP TCP/IP support. If you enable both options when you build a Blackfin VI into a Blackfin application, the Blackfin application runs very slow or not at all.

Could the third bullet explain the behavior of your system?  Try disabling data caching and see if your performance improves.

Thanks!

Janell R

[sesexton]

Janell

That's exactly what I did. I will try again with the cache disabled. Thank you for pointing this out

Sean Sexton

[johu]

Sean,

Do you mind posting your vi?