Transmit Continuous Problem N200

[EtuelDue]

Hello,

I have build a systems which should continously transmit packages containing only zeros and only at certain time interval (e.g. every 2 seconds) transmit a valid ofdm package. My problem is that the transmit vi "niUSRP Write Tx Data" is too fast. If I want to transmit 10000 samples with an IQ-Rate of 1 MS/sec my transmit-time should be 10 ms. But in Labview the VI only takes about 1 ms to transmit the data to the buffer of the usrp boards and then jumps back and already transmits the next package. Because of this I can't transmit my ofdm package at a certain time stamp as I have no idea on how much data is buffered at the usrp at the moment etc. If I use the "End of Data=true" property of the "niUSRP Write Tx Data"-VI the time is much greater than 10 ms.

Anyone any idea?

Thanks

[msind]

HI EtuelDue,

is it possible if you upload your Code that I could take a look at it?

Maybe you could try to decouple your reading and writing with a producer/consumer architecture.

With this you can buffer your read values and write them wenn you got time to write.

[EtuelDue]

Hello msind,

I hope this screenshot is also sufficient.

Before this part I am only initializing the USRP board with my IQ-Rate (1.62MS/sec) etc. (#2), generating the OFDM-Blocks/Zero-Blocks (#1) and providing my interval time (#3, e.g. 0.5 seconds). In the sequence structure (#4) I transmit my choosen block (normal Zero-Block), get the USRP-Board time and add the additional time since the last transmission to my total time value (#5) which is basically my counter. If this time becomes greater than my time intervall from #3 I want to switch from only transmitting blocks containing zeros to my OFDM Block. But from #6 I know that although my transmission of e.g. 10000 samples with a sample rate of 1 MS/sec should take about 10 ms the time difference in #6 is only about 1 ms. So basically the data is send to the board in 1 ms and then jumps back to the beginn of my while loop and transmits data again. Because of this I can never be sure when my OFDM-Block is transmitted (Don't know the state of the buffer).

What I want is for the VI to only transmit data after the buffer is empty. If I try the same setup with "end of data=true" I get an addiotional 60 ms delay.

I hope this clears up some things.

[msind · Accepted solution]

I think the best way to be sure that no value gets lost is the producer consumer architecture.

Maybe you should give it a try

If you don't know it you can read some basics here:

http://www.ni.com/white-paper/3023/en/

This should do what you want i think 😉

[EtuelDue]

Thank you very much. This seems to fit very much.

[msind]

No problem.

If this is a solution for your problem you could mark it as that, so everyone knows that this question is solved 😉