buffer underflow

[Emran1612]

Hello,

i want to Transmit voice from my pc using FM modulation. I wrote the following VI. which works for less then one minute and then shows the following error message:

Error: Underflow: the Tx buffer was emptied before new data was provided. Consider reducing the IQ rate, increasing the Write rate, or increasing the number of samples per Write.

It would be great if someone help me out to solve the problem. I attached the VI.

Regards,

Emran

[psisterhen]

You may want to see some tips on Tx streaming performance here:

http://forums.ni.com/t5/USRP-Software-Radio/Is-there-any-successful-example-of-USRP-RIO-with-PCIe-ad...

Some of the numbers are specific to the 294x/295x series.  If you are using a 292x/293x device, consider using waveforms in multiples of 363 samples.

[Emran1612]

Hello psisterhen

Iam using ETTUS N200 usrp

[Sarah_Y]

Hi Emran1612,

The tips that psisterhen mentioned apply to the Ettus N2x0 as well as the NI 292x/3x products (all of the 1 Gigabit Ethernet based USRPs).  The benchmark tool that he posted is the best way to determine the limitations of your system and can help you determine the correct number of samples and IQ rate that will work best for your application.

Also look at this forum post for other possible ways to reduce buffer underflows.

http://forums.ni.com/t5/USRP-Software-Radio/Increasing-write-rate/td-p/2165368

[josephkirmani]

I am trying to transmit video over USRP 2920 from webcam but I am getting "Error code -1074118645"  I even tried to change increase or decrease) the I/Q rate but it gives the same error message. The error message which i am getting is given below:

Error code -1074118645 niUSRP Write Tx Data (CDB).vi<ERR>Underflow: the Tx buffer was emptied before new data was provided.  Consider reducing the IQ rate, increasing the Write rate, or increasing the number of samples per Write.

 Can any body guide me how to fix this error. Thanks in advance. 

PS: Please find attached my VI.

[Skirpt]

Hi Joseph,

Looking at this forum http://forums.ni.com/t5/USRP-Software-Radio/Transmitting-and-receiving-simutaneously-USRP-WBX-LabVIE... Sarah recommends using  an IQ rate of 1 MS/s, 100k for the waveform size, and 100k number of samples. This seems to work for the other person. Can you see if you get the same results after changing these settings?

[josephkirmani]

I tried running my design with 1MS/s and even with 2MS/s but I always experienced same error message every time.

[josephkirmani]

Please can anybody guide me how to fix this buffer underflow problem. It is very frustrating. I will appreciate if someone provide me the solution of the above mentioned problem.

Thanks

[4Matted]

This forum seems to discuss your buffer underflow issue. http://forums.ni.com/t5/USRP-Software-Radio/Error-Underflow-the-Tx-buffer-was-emptied-before-new-dat...  I would recommend looking over this and seeing if any of the steps mentioned here can be used in you application to prevent the error.