On Fri, Aug 03, 2007 at 11:12:30AM -0400, George Nychis wrote: > What is 'pingval' and what is its units? I didn't think most pings had > a value, only empty responses for which you could compute whatever delay > value you please by calculating the time between. > http://gnuradio.org/trac/browser/gnuradio/branches/developers/gnychis/inband/usrp/host/lib/inband/usrp_server.mbh#L105
The pingval is arbitrary. > Second question. For an application to properly timestamp outgoing > packets, the application needs some general idea of the current clock > value on the USRP. At first I was thinking "oh well the app can just > send a ping and read the timestamp off of the response while calculating > the delay." Well, the ping doesn't carry the clock back up to the > application. RX packets (response-recv-raw-samples) carry the timestamp > back up to the application, but there is no notion of calculating delay > here. The usrp_server should be passing the timestamp back to the application. It's in the header of the packet containing the ping reply. We should add the timestamp to the response-from-control-channel > Is the clock stored in a readable register somewhere on the USRP that a > register read could be used? The delay could be calculated here between > the request and response. I checked our wiki but see no register: > http://gnuradio.org/trac/wiki/UsrpFPGA I think having the clock counter mapped to a register is a fine idea. Note that the list of regs at http://gnuradio.org/trac/wiki/UsrpFPGA is the existing list of regs, and hasn't been refactored to reflect the requirements for inband signaling. Also, I think it's a bad idea to use the wiki for data where the ultimate source is the source code. A link to the source would make more sense, otherwise the wiki is pretty much guaranteed to be out-of-date. (Basically we're violating the "write it once" principle) Eric _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
