Blackfin Timer Access

[Michael.Phillips]

Hi Sean,

Declare a global data structure and have your interrupt routine write into that structure. Then, you can use an Inline C Node to read from that structure in the main thread.

[sesexton]

Michael

I have the timer access working now, thanks for your help on this problem. I do have a new problem however. It seems that the throughput of the TCP/IP subsystem is VERY slow. I am using the canned LabView TCP functions to transfer the timer data to a host computer. It is taking about 15 seconds to transfer 3 seconds worth of timer 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

[Michael.Phillips]

Hi Sean,

R&D looked into this. Our tests show a roundtrip lwIP throughput of 341 kbytes/sec.  There is a webpage which confirms these findings.  This statement is from the webpage:
 
http://www.usenix.org/events/mobisys03/tech/full_papers/dunkels/dunkels_html/node27.html
 
The throughput quickly reaches a maximum of about 415 kilobytes per second. This limit is likely to be the processing limit of the lwIP code in the embedded system and therefore is the maximum possible throughput for lwIP in this particular system.