Hi All, I have been trying to get the USRP to retune at a specific time as accurately as possible. Given the issues with latency over the network and so forth, I was hoping to find a way to set a specific time for a retune command. In my search for a way to do this, I came across the "set_command_time()" api call in uhd. It seems that it is currently not implemented. Would that call give me the functionality I require? Is there any way to achieve the desired functionality without FPGA work? I am using an N210. Thanks Hossein

On 01/24/2012 11:38 AM, Hossein Safavi wrote: > Hi All, > > I have been trying to get the USRP to retune at a specific time as > accurately as possible. Given the issues with latency over the > network and so forth, I was hoping to find a way to set a specific > time for a retune command. > > In my search for a way to do this, I came across the > "set_command_time()" api call in uhd. It seems that it is currently > not implemented. Would that call give me the functionality I require? > Is there any way to achieve the desired functionality without FPGA > work? I am using an N210. > Yea, set_command_time() is the way to do it. However, the necessary FPGA fabric is not yet implemented. This and sc8 samples for TX are 2 FPGA features planned for the near future. In the meantime, a combination of estimating the RTT of a control packet and using the incoming RX timestamps to gauge when to send the re-tune packet; that may be your best option. If you are looking to re-tune as fast as possible, I recommend re-tuning the DSP/cordic only, which gives you about 40Mhz of bandwidth to frequency hop with. Retuning the daughterboard synthesizer is obviously a more time-consuming process. -Josh