# USRP underflow issue **URL:** \ **Category:** GNU Radio\ **Created:** [June 4, 2015, 10:32am UTC](https://www.ruby-forum.com/t/usrp-underflow-issue/242205 "2015-06-04T10:32:37Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [June 4, 2015, 10:32am UTC](https://www.ruby-forum.com/t/usrp-underflow-issue/242205/1 "2015-06-04T10:32:37Z")
Hi everyone, I’m new to Gnuradio and I have some problems with USRP N210 with WBX daughterboards. I send data coming from udp socket to USRP and I am encountering underflow issue. I think that problem is due to the rate of the data transmitted to USRP. I have tried to set the sample rate in the USRP using different values. Only with the lowest value, 200 ksps, it seems to work (no underflow) but increasing the sample rate underflow appears. Moreover, I have repeated the test with 200 ksps more than once with the same configuration and in some cases underflow appears. Could you please help me? Thanks Irene ---
**Author:** ![irene\_menicagli](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/34f0e0/32.png) [@irene\_menicagli](https://www.ruby-forum.com/u/irene_menicagli)\ **Post date:** [June 4, 2015, 10:53am UTC](https://www.ruby-forum.com/t/usrp-underflow-issue/242205/2 "2015-06-04T10:53:04Z")
Hi Irene, "U"nderflows occur when your application doesn’t supply samples fast enough to the USRP. This is well-reflected by the fact that with the lowest sampling rate things work. Now, there might be different reasons, and the most prominent one is that your data source ultimately doesn’t provide any faster. Also, if your processing is very complex, your computer might become a bottleneck. Often, people get confused and use the “throttle” block in a flow graph that actually contains hardware. Never ever do that! Best regards, Marcus