Richard, please note that the script is an easy example on how to control things through tags, and not optimized for performance (but rather, for readability).
You should be able to go way below the re-tune time of your analog part with timed commands, but to get maximum performance out of this you might have to go a different route than using tags. The reason being, with tags, you're still left to the whims of scheduling randomness, but you want something with very tight control. The way I'd go ahead here is pre-load the (timed) tune commands into the command FIFO by using set_command_time() before every tune command, and then start streaming (also with a timestamp) to line up data and commands. Here's the catch: The command FIFO is not super-deep, and tunes translate into multiple commands, so I'm not sure how many you can actually queue. However, sending commands will block if the queue is full, so you can have a thread updating the command queue with new tunes continuously -- unless I've forgotten something here. I admit the tags are a lot easier! But tight control over latencies etc. is something where GNU Radio traditionally comes up short, and usually requires some custom logic. Cheers, Martin On 22.12.2015 14:50, Richard Bell wrote: > I'm using Ubuntu 14.04 LTS, GNU Radio 3.7.9rc1, UHD 3.9.1 with two USRP > N210s with WBX daughtercards. > > I'm trying to determine what the fastest hopping rate is with the given > setup above. Using the provided gr-uhd/examples/python frequency hopping > script, it seems that 100 ms (10 Hz) is the fastest. What I haven't been > able to figure out yet, is if this is due to a limitation imposed by > that script, or if this is the fastest way (or right around the fastest > way) that any script could hope to approach. > > What I did to arive at this 100 ms limit is the following: > 1) The first N210 is used as a transmitter and I use the following > command to initiate hopping > ./freq_hopping.py -a "addr=10.0.8.5" --antenna TX/RX --verbose > --freq 915e6 --gain 20 --rate 5e6 --num-bursts 10000 --freq-delta 0.1e6 > --samp-per-burst 10 --hop-time 50 > > 2) The second N210 is a spectrum analyzer using the following command > and the waterfall tab > uhd_fft -f 915M -s 0.5M -A TX/RX > > 3) I stop the waterfall plot, so it stops scrolling, and measure the > smallest length of time at one frequency I can achieve given any batch > of settings in step 1. The settings I linked in step one should have set > a hop time of 50 ms, but this measurements shows 100 ms. > > I'm going to try writing my own custom script, but would like to know if > others have pushed this before and found ~100 ms (10 Hz) as the limit > for frequency hopping intervals using the N210+WBX combo. > > Appreciated, > Rich > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio