Re: [Discuss-gnuradio] Time of Arrival Hooks
Doug, Thanks I'll try this. Googling a bit more I think fwrite has to be thread safe, I'll double check my setup again and have another think if this doesn't help. Cheers, Tim On Thu, Nov 19, 2009 at 7:17 PM, Doug Geiger wrote: > Tim Pearce wrote: > >> Hi Guys, >> >> After experimenting a bit more I think the issue was my test setup. >> >> Previously I was using python to setup a USRP Source (with timestamps) and >> save both the samples (64 bit) and timestamps (32bit) to a file sink to >> process by importing with numpy and checking timestamps later. >> >> At 25MHz thats ~ 300MB/sec of data, which is substantially more than >> machines disk, which is probably about 20MB/sec max. >> > Don't have a good answer on the thread-safety question - but one method > I've used when I want to collect a bunch of data for a limited period of > time is mount a ram disk/tmpfs. E.g. I'd do something like: > $ mkdir /tmp/shm > $ sudo mount -t tmpfs tmpfs /tmp/shm > $ usrp2_rx_cfile -e -f -N > /tmp/shm/data.dat > > Cheers, >> >> Tim >> > Doug > > -- > Douglas Geiger > Code 5545 > U.S. Naval Research Laboratory > Washington, DC 20375 > (202) 767-9048 > douglas.gei...@nrl.navy.mil > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Time of Arrival Hooks
Tim Pearce wrote: Hi Guys, After experimenting a bit more I think the issue was my test setup. Previously I was using python to setup a USRP Source (with timestamps) and save both the samples (64 bit) and timestamps (32bit) to a file sink to process by importing with numpy and checking timestamps later. At 25MHz thats ~ 300MB/sec of data, which is substantially more than machines disk, which is probably about 20MB/sec max. Don't have a good answer on the thread-safety question - but one method I've used when I want to collect a bunch of data for a limited period of time is mount a ram disk/tmpfs. E.g. I'd do something like: $ mkdir /tmp/shm $ sudo mount -t tmpfs tmpfs /tmp/shm $ usrp2_rx_cfile -e -f -N /tmp/shm/data.dat Cheers, Tim Doug -- Douglas Geiger Code 5545 U.S. Naval Research Laboratory Washington, DC 20375 (202) 767-9048 douglas.gei...@nrl.navy.mil ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Time of Arrival Hooks
Oops sorry guys this is in reply to the wrong timestamp question -- I had meant to reply to this thread: http://lists.gnu.org/archive/html/discuss-gnuradio/2009-11/msg00069.html Cheers, Tim On Thu, Nov 19, 2009 at 7:02 PM, Tim Pearce wrote: > Hi Guys, > > After experimenting a bit more I think the issue was my test setup. > > Previously I was using python to setup a USRP Source (with timestamps) and > save both the samples (64 bit) and timestamps (32bit) to a file sink to > process by importing with numpy and checking timestamps later. > > At 25MHz thats ~ 300MB/sec of data, which is substantially more than > machines disk, which is probably about 20MB/sec max. > > I've written a quick test block to run the same basic check in memory (i.e > check if latest timestamp is sooner than the last one -- expected to fail at > roll over!) and have had no problems using a 25MHz bandwidth. > > I would have thought the large amount of memory in the machine would have > let me get over the hard drive bottleneck for a short period (say 30 > seconds). The amount of data seems generated seems reasonable but the file > sink seems to be causing corruption in terms of misordered samples. > > I've had a quick look at the code and gr.file_sink(..) seems to use fwrite, > is this thread safe? Thats the only idea I cant think of atm that might be > causing this, has anyone else got any ideas? > > I'm going to have a quick google to see if theres a safer way to implement > I can test quickly, has anyone looked at this before? (Those expensive PCI > Expressive SSD Cards that can handle 1.4Gbit/sec would be nice if they > werent quite as expensive :) ) > > Cheers, > > Tim > > > > On Wed, Nov 11, 2009 at 10:22 PM, Doug Geiger > wrote: > >> devin kelly wrote: >> >>> Hello everyone, >>> >>> I'm doing a project with the USRP2 that where I need to know the Time of >>> Arrival(TOA) of the waveforms. This is for a geolocation application. >>> >>> My understanding as of now is that the hooks to get TOA are there in the >>> USRP2, but the firmware does not provide access to them at this point. Is >>> this correct? >>> >>> If the firmware can provide TOA, how can I get that information?? >>> >>> Thanks, >>> Devin >>> >>> >>> >>> ___ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >> The timestamp on the frame of *samples* is indeed available - and if you >> use the low-level interface to the USRP2 (libusrp2) you can see those >> timestamps. However, the gr-usrp2 interface (i.e. the default source block >> for working with the USRP2) does not. If you want to see the timestamps in a >> GNURadio flowgraph, you'll need to create a custom block based on the >> usrp2_source_[32fc or 16sc] block. >> However, that won't give you the TOA of a received signal *directly*. >> You'll need some scheme to decide that a signal has arrived, and then >> calculate the TOA based on the timestamp corresponding to that sample (the >> timestamps you get from libusrp2 are for the first signal in the frame of >> samples - so you'd need to either calculate the running timestamp for each >> sample, or keep track of the offset within the frame somehow). >> Good luck! >> Doug >> >> -- >> Douglas Geiger >> Code 5545 >> U.S. Naval Research Laboratory >> Washington, DC 20375 >> (202) 767-9048 >> douglas.gei...@nrl.navy.mil >> >> >> >> >> ___ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Time of Arrival Hooks
Hi Guys, After experimenting a bit more I think the issue was my test setup. Previously I was using python to setup a USRP Source (with timestamps) and save both the samples (64 bit) and timestamps (32bit) to a file sink to process by importing with numpy and checking timestamps later. At 25MHz thats ~ 300MB/sec of data, which is substantially more than machines disk, which is probably about 20MB/sec max. I've written a quick test block to run the same basic check in memory (i.e check if latest timestamp is sooner than the last one -- expected to fail at roll over!) and have had no problems using a 25MHz bandwidth. I would have thought the large amount of memory in the machine would have let me get over the hard drive bottleneck for a short period (say 30 seconds). The amount of data seems generated seems reasonable but the file sink seems to be causing corruption in terms of misordered samples. I've had a quick look at the code and gr.file_sink(..) seems to use fwrite, is this thread safe? Thats the only idea I cant think of atm that might be causing this, has anyone else got any ideas? I'm going to have a quick google to see if theres a safer way to implement I can test quickly, has anyone looked at this before? (Those expensive PCI Expressive SSD Cards that can handle 1.4Gbit/sec would be nice if they werent quite as expensive :) ) Cheers, Tim On Wed, Nov 11, 2009 at 10:22 PM, Doug Geiger wrote: > devin kelly wrote: > >> Hello everyone, >> >> I'm doing a project with the USRP2 that where I need to know the Time of >> Arrival(TOA) of the waveforms. This is for a geolocation application. >> >> My understanding as of now is that the hooks to get TOA are there in the >> USRP2, but the firmware does not provide access to them at this point. Is >> this correct? >> >> If the firmware can provide TOA, how can I get that information?? >> >> Thanks, >> Devin >> >> >> >> ___ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > The timestamp on the frame of *samples* is indeed available - and if you > use the low-level interface to the USRP2 (libusrp2) you can see those > timestamps. However, the gr-usrp2 interface (i.e. the default source block > for working with the USRP2) does not. If you want to see the timestamps in a > GNURadio flowgraph, you'll need to create a custom block based on the > usrp2_source_[32fc or 16sc] block. > However, that won't give you the TOA of a received signal *directly*. > You'll need some scheme to decide that a signal has arrived, and then > calculate the TOA based on the timestamp corresponding to that sample (the > timestamps you get from libusrp2 are for the first signal in the frame of > samples - so you'd need to either calculate the running timestamp for each > sample, or keep track of the offset within the frame somehow). > Good luck! > Doug > > -- > Douglas Geiger > Code 5545 > U.S. Naval Research Laboratory > Washington, DC 20375 > (202) 767-9048 > douglas.gei...@nrl.navy.mil > > > > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Time of Arrival Hooks
devin kelly wrote: Hello everyone, I'm doing a project with the USRP2 that where I need to know the Time of Arrival(TOA) of the waveforms. This is for a geolocation application. My understanding as of now is that the hooks to get TOA are there in the USRP2, but the firmware does not provide access to them at this point. Is this correct? If the firmware can provide TOA, how can I get that information?? Thanks, Devin ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio The timestamp on the frame of *samples* is indeed available - and if you use the low-level interface to the USRP2 (libusrp2) you can see those timestamps. However, the gr-usrp2 interface (i.e. the default source block for working with the USRP2) does not. If you want to see the timestamps in a GNURadio flowgraph, you'll need to create a custom block based on the usrp2_source_[32fc or 16sc] block. However, that won't give you the TOA of a received signal *directly*. You'll need some scheme to decide that a signal has arrived, and then calculate the TOA based on the timestamp corresponding to that sample (the timestamps you get from libusrp2 are for the first signal in the frame of samples - so you'd need to either calculate the running timestamp for each sample, or keep track of the offset within the frame somehow). Good luck! Doug -- Douglas Geiger Code 5545 U.S. Naval Research Laboratory Washington, DC 20375 (202) 767-9048 douglas.gei...@nrl.navy.mil ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Time of Arrival Hooks
Devin, The metadata is already passed to GNURadio by the USRP2 firmware. Its the gnuradio usrp2 source block that doesn't do anything with this information (metadata has the timestamp for the first sample of each frame) You can modify the code to provide a second stream, or interleave the data with them somehow by modifying the rx**_fc_handler.h files (primarily) to get access to this timestamp data in C++ blocks or post processing in python (all I've done so far). Look for the "Fixme: Do something with metadata" line! I've posted a couple of questions about getting timestamps to this mailing list (I don't need absolute times in my case though so haven't thought about how to sync these timestamps to real times) which some people (Doug, Juha I think) have helped me out on and I'm just summarising their replies here! I think I've read something about the 3.3 release implementing this but that might have been about the ability to do TDMA Cheers, Tim On Wed, Nov 11, 2009 at 7:21 PM, devin kelly wrote: > Hello everyone, > > I'm doing a project with the USRP2 that where I need to know the Time of > Arrival(TOA) of the waveforms. This is for a geolocation application. > > My understanding as of now is that the hooks to get TOA are there in the > USRP2, but the firmware does not provide access to them at this point. Is > this correct? > > If the firmware can provide TOA, how can I get that information?? > > Thanks, > Devin > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Time of Arrival Hooks
Hello everyone, I'm doing a project with the USRP2 that where I need to know the Time of Arrival(TOA) of the waveforms. This is for a geolocation application. My understanding as of now is that the hooks to get TOA are there in the USRP2, but the firmware does not provide access to them at this point. Is this correct? If the firmware can provide TOA, how can I get that information?? Thanks, Devin ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
