April 2013 - osmocom-sdr - lists.osmocom.org

by Benedikt Heinz

Hi everyone, although there are some comparisons between the R820T and the E4000 already [1, 2], I also did some tests with another use-case in mind. I'm working on a thing similar to RTLSDR-Scanner [3]. I want to monitor a large part of the spectrum continuously. So I compared the R820T with the E4000 using RTLSDR-Scanner w/ and w/o an antenna. My results are here: https://docs.google.com/folder/d/0ByDAKwyEiyx_XzZ5ZnpRV1VZWDQ/edit?usp=shar… There's much more spurs with the E4000 than w/ the R820T. According to [1, 2] one also would expect a better overall sensivity compared to the E4000. However, the GSM900 signals for example seem to be way better with the E4000 according to the RTLSDR-Scanner. Tuning to a certain channel w/ OsmoSDR Source in GNUradio gives about the same SNR - contrary to the RTLSDR-Scanner output. Can anyone explain this? Also, the DVB-T channel at 502MHz is quite weak in the R820T RTLSDR-Scanner output when compared to the E4000. I had a closer look at the lower limit of the channel in gnuradio. This can be seen in the 502MHz_*.png pictures. The E4000 produces a nice +20dB step while one can hardly see the channel in the R820T spectrum. I don't understand this as well. Is this AGC-related? Manually setting a fixed gain didn't really help though... Any explanations? Thank you! Best regards, Hunz [1] http://steve-m.de/projects/rtl-sdr/tuner_comparison/ [2] http://www.hamradioscience.com/rtl2832u-r820t-vs-rtl2832u-e4000/#more-1852 [3] https://github.com/EarToEarOak/RTLSDR-Scanner

10 years, 8 months

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OpenBSD: crashing

by Alan Corey

This is with a version of rtl-sdr I got by git last night and OpenBSD 5.2 (current release). 5.2 has some pthreads fixing so I waited until I bought another computer and loaded it. Are the crashes related to threads? I don't know, but possibly. It didn't work with OpenBSD 5.0 either. rtl_fm crashes and uses threads rtl_adsb crashes and uses threads rtl_tcp doesn't crash, uses threads, actually stops on ctrl-c rtl_test doesn't crash, doesn't use threads, won't stop rtl_eeprom doesn't crash, doesn't use threads, ends normally I'm not real practiced using gdb but I tried looking at a couple of core files, here's a run of rtl_fm: rtl_fm -f 162550000 -N - | play -t raw -r 24k -e signed-integer -b 16 -c 1 -V1 - -: (raw) Encoding: Signed PCM Channels: 1 @ 16-bit Samplerate: 24000Hz Replaygain: off Duration: unknown In:0.00% 00:00:00.00 [00:00:00.00] Out:0 [ | ] Clip:0 Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: 00000013 Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle Found Rafael Micro R820T tuner Oversampling input by: 42x. Oversampling output by: 1x. Buffer size: 8.13ms Tuned to 162802000 Hz. Sampling at 1008000 Hz. Output at 24000 Hz. Exact sample rate is: 1008000.009613 Hz Tuner gain set to automatic. In:0.00% 00:00:00.00 [00:00:00.00] Out:0 [ | ] Clip:0 Done. Abort (core dumped) d530# gdb -c rtl_fm.core /usr/local/bin/rtl_fm GNU gdb 6.3 Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-unknown-openbsd5.2"... Core was generated by `rtl_fm'. Program terminated with signal 6, Aborted. Reading symbols from /usr/lib/libpthread.so.16.0...done. Loaded symbols for /usr/lib/libpthread.so.16.0 Reading symbols from /usr/lib/libm.so.7.0...done. Loaded symbols for /usr/lib/libm.so.7.0 Reading symbols from /usr/local/lib/librtlsdr.so.0.0...done. Loaded symbols for /usr/local/lib/librtlsdr.so.0.0 Reading symbols from /usr/local/lib/libusb-1.0.so.1.0...done. Loaded symbols for /usr/local/lib/libusb-1.0.so.1.0 Symbols already loaded for /usr/lib/libpthread.so.16.0 Reading symbols from /usr/lib/libc.so.65.0...done. Loaded symbols for /usr/lib/libc.so.65.0 Loaded symbols for /usr/libexec/ld.so #0 0x0abbd98d in kill () from /usr/lib/libc.so.65.0 (gdb) bt #0 0x0abbd98d in kill () from /usr/lib/libc.so.65.0 #1 0x0ac29545 in abort () at /usr/src/lib/libc/stdlib/abort.c:68 #2 0x005e9298 in pthread_mutex_unlock (mutexp=0x3c003d8c) at /usr/src/lib/librthread/rthread_sync.c:218 #3 0x1c00266e in full_demod (fm=0xcfa2de5c) at /usr/src/misc/osmocom/2013-04-15/rtl-sdr/src/rtl_fm.c:583 #4 0x1c0028ff in demod_thread_fn (arg=0xcfa2de5c) at /usr/src/misc/osmocom/2013-04-15/rtl-sdr/src/rtl_fm.c:641 #5 0x005ebc2e in _rthread_start (v=0x84da4c00) at /usr/src/lib/librthread/rthread.c:111 #6 0x0aba62e9 in __tfork_thread () from /usr/lib/libc.so.65.0 The backtrace (bt) shows that it dies trying to do a mutex_unlock (I think). rtl_tcp also does a mutex_unlock and it doesn't crash. I'm probably reading it wrong for all I know. I don't know what's causing the signal 6 either. I'd also like to get the -lrt of of the cmake files. OpenBSD doesn't use or have lrt, it works without. I can edit it out and compile, but every time I run cmake again, I have to edit the files again. Alan ----- Radio Astronomy - the ultimate DX

10 years, 9 months

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[rtl-sdr] store frequency correction in eeprom?

by Benedikt Heinz

Some of you are probably using multiple dongles with alternating applications as well. Regarding the frequency correction, I put a sticker on each dongle and wrote the ppm value on it. However manually setting the value in each application is still annoying. So I used rtl_eeprom to write the value into the product-ID with the following format: "RTL%+dppm" resulting in sth. like this: RTL+87ppm I'm not sure if this is the best way to do it, but this approach works without changing librtlsdr. Another option might be storing the value in a non-used eeprom location and adding get/set functions to librtlsdr. Is it possible to write arbitrary values to unused eeprom locations without fucking up the realtek eeprom handling? Do you think this would be a better way? I'd like to hear your comments on this. It would be awesome if we could find a solution that many existing applications could incorporate. (Of course the ppm value still changes with temperature, but having a base value is still closer to the truth than 0ppm I'd say. I measured the offset directly after grabbing samples for 20 minutes at room-temperature and jitter is <1ppm.) Best regards, Hunz

10 years, 11 months

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R820T register map available

by Adam Nielsen

Hi all, One of the designers of the R820T tuner has recently been posting on the ultra-cheap-sdr group, and has kindly supplied a map of the R820T registers for private use only within the SDR community. He has asked that it not be posted on any website, but only be forwarded around privately. To that end, if anyone would like a copy of this spreadsheet and would be willing to likewise not publish it on the web, let me know off-list and I'll send it to you. There's not a huge amount in the way of explanations, but it lists all the registers and a very brief description of what they do. Cheers, Adam.

11 years

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Re: [Discuss-gnuradio] nVidia's Tegra 4 has SDR - the i500 LTE soft modem from Icera

by est

Hello group, What do you guys think of the nVidia Tegra 4's i500 SDR? http://www.engadget.com/2013/01/07/nvidia-i500-soft-modem/ http://www.nvidia.com/docs/IO/116757/NVIDIA_i500_whitepaper_FINALv3.pdf Is it hackable?

11 years

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Compiling on osx - solved...

by Alberto Albiol

Hello I have been fighting to compile the gr-osmosdr package in my osx These are the minor fixes I had to do: 1- Change in Cmakelists.txt: find_package(Boost COMPONENTS thread system), If thread and system is not included then there are linking problems. Although I see that this was removed recently... 2- cmake -DCMAKE_INSTALL_PREFIX=/opt/local (so it is installed together wit my ports intallation, this is really optional) 3- Before compiling I manually edit CmakeCache.txt, and change all the references of /usr/lib/python to /opt/local/lib/python. If not it links agains the system python instead of the ports's python! 4- Add this line in my .bashrc so python can find the package export PYTHONPATH="/opt/local/lib/python2.7/site-packages/" I am aware that this is not the most elegant way to solve the problem but is the only one that I was able to come up. Hope it helps Regards

11 years

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Re: rtl_fm scanning

by Colin Stagner

I am also having the rtl_fm scanning bug which was first reported in http://lists.gnumonks.org/pipermail/osmocom-sdr/2013-February/000485.html The scanning mode in rtl_fm hangs during the re-tuning process. This makes it impossible to use rtl_fm in scanning mode. I am using Ubuntu 12.10 with libusb 2:1.0.12-2, the latest git master version of rtl-sdr, and an Elonics E4000 (Realtek, RTL2838UHIDIR). Here are the steps to reproduce: 1. Find some frequency FREQ_NOISE that is not in use, and some frequency FREQ_SIGNAL which is in use constantly (i.e., like a commercial FM station). Find an appropriate squelch value SQUELCH which will stop FREQ_NOISE but pass FREQ_SIGNAL. 2. rtl_fm -f ${FREQ_NOISE} -l ${SQUELCH}. The program should not pass any audio, but it will exit cleanly with ^C. 3. rtl_fm -f ${FREQ_SIGNAL} -l ${SQUELCH}. The program should pass audio and exit cleanly with ^C 4. rtl_fm -f ${FREQ_SIGNAL} -f ${FREQ_NOISE} -l 0. The scan will pause on the first channel and pass audio. 5. rtl_fm -f ${FREQ_NOISE} -f ${FREQ_SIGNAL} -l ${SQUELCH}. The program will not output any audio, even though the first frequency is squelched out and the scanning function should skip immediately to the second frequency. Additionally, it will not exit if sent a SIGINT with ^C, and it must be killed with a SIGKILL. I've made a stack trace of this behavior. The program hangs very consistently at the same location each time: http://pastebin.com/wzE09MCi Thread 1 (the USB buffer reading thread) hangs while waiting for the data_write mutex lock in rtl_fm.c:642. I presume the thread has exhausted its supply of data and isn't getting any more. Thread 2 is slightly more interesting, because it hangs during the libusb system calls within the tuning function rtlsdr_set_center_freq() in librtlsdr.c:796. My guess is that it's making a blocking call that never returns. Can anyone else reproduce this bug?

11 years

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submitting patches

by Michael Davis

Hi All, Can anyone point me in the direction of a place I can go to submit patches? I fixed a bug in CMake for gnuradio-osmosdr that stopped the build on my system. Best, Mike

11 years

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Scanning with rtl_fm

by Alan Corey

I'm using rtl_fm in a scanning (nbfm) situation, and even with the antenna input disconnected and terminated, I get a burst of noise that sounds like a squelch tail maybe once each scan cycle. They're a little over 1 second apart. I've tried setting the squelch up to 10000 where I don't get signals anymore, but I still get the noise. I discovered that if you scan and have the output be a raw audio file, nothing gets recorded when nothing breaks squelch. This makes time-lapse recordings where all the pauses are taken out. Very nice, except for the noise bursts. I'm using: #!/bin/sh rtl_fm -N -S -l 132 -p 102 -f 854040000 -f 854240000 -f 854315000 -f 854415000 -f \ 854490000 -f 854540000 -f 855165000 -f 855240000 -f 858790000 -f 867350000 \ -f 867715000 /tmp/`date +"%Y-%m-%d_%H%M.raw"` and recorded overnight, but I mostly got noise bursts. Alan ----- Radio Astronomy - the ultimate DX

11 years

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gr-iqbal or gr-iqbalance?

by Wojciech Kazubski

Hello! This is a minor issue, but may lead to some misunderstanding (and seach failures) in future. The package to correct IQ imbalance is registered at http://cgit.osmocom.org as gr-iqbal but project name set in line 24 of toplevel CMakeList.txt is gr- iqbalance. Which name should be used while building packages, etc.? BTW: Is there any homepage for gr-iqbal/gr-iqbalance? Wojciech Kazubski

11 years

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OpenSourceDABplusSDRreceiver

by mrzfrn

"However, nobody has implemented a full and open DAB+ SDR receiver yet" Not true, look at http://www.sdr-j.tk/index.html Francesco

11 years

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[PATCH 1/1] add -S (synchronous) mode to rtl_fm

by Stuart Henderson

The enclosed diff adds a synchronous mode to rtl_fm. This helps OpenBSD (where libusb async isn't yet working). Signed-off-by: Stuart Henderson <stu(a)spacehopper.org> --- src/rtl_fm.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/src/rtl_fm.c b/src/rtl_fm.c index e8ebb77..a71e287 100644 --- a/src/rtl_fm.c +++ b/src/rtl_fm.c @@ -128,6 +128,7 @@ void usage(void) "\t[-E sets lower edge tuning (default: center)]\n" "\t[-N enables NBFM mode (default: on)]\n" "\t[-W enables WBFM mode (default: off)]\n" + "\t[-S force sync output (default: async)]\n" "\t (-N -s 170k -o 4 -A fast -r 32k -l 0 -D)\n" "\tfilename (a '-' dumps samples to stdout)\n" "\t (omitting the filename also uses stdout)\n\n" @@ -723,12 +724,14 @@ int main(int argc, char **argv) uint32_t dev_index = 0; int device_count; int ppm_error = 0; + int sync_mode = 0; char vendor[256], product[256], serial[256]; + fm_init(&fm); pthread_mutex_init(&data_ready, NULL); pthread_mutex_init(&data_write, NULL); - while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:EFA:NWMULRDC")) != -1) { + while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:EFA:NWMULRDSC")) != -1) { switch (opt) { case 'd': dev_index = atoi(optarg); @@ -815,6 +818,9 @@ int main(int argc, char **argv) case 'R': fm.mode_demod = &raw_demod; break; + case 'S': + sync_mode = 1; + break; default: usage(); break; @@ -921,9 +927,24 @@ int main(int argc, char **argv) fprintf(stderr, "WARNING: Failed to reset buffers.\n");} pthread_create(&demod_thread, NULL, demod_thread_fn, (void *)(&fm)); - rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm), - DEFAULT_ASYNC_BUF_NUMBER, - lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH); + if (sync_mode) { + fprintf(stderr, "Reading samples in sync mode...\n"); + while (!do_exit) { + r = rtlsdr_read_sync(dev, &fm.buf, + lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH, + &fm.buf_len); + if (r < 0) { + fprintf(stderr, "WARNING: sync read failed.\n"); + break; + } + full_demod(&fm); + } + } else { + fprintf(stderr, "Reading samples in async mode...\n"); + rtlsdr_read_async(dev, rtlsdr_callback, (void *)(&fm), + DEFAULT_ASYNC_BUF_NUMBER, + lcm_post[fm.post_downsample] * DEFAULT_BUF_LENGTH); + } if (do_exit) { fprintf(stderr, "\nUser cancel, exiting...\n");} -- 1.8.1.3

11 years

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rtl_test patch

by Nuno Gonçalves

Corrects bugs where: Cumulative PPM error is always "342" if execution stopped before first PPM_DURATION. PPM error alias to wrong values if over +-1045 (this happens quite a lot actually due to bug reported at [1]). Behavior changes: Cumulative PPM error value is now printed every PPM_DURATION so the user can check when it is settled. [1] http://lists.osmocom.org/pipermail/osmocom-sdr/2013-April/000584.html Thanks, Nuno Signed-off-by: Nuno Goncalves <nunojpg(a)gmail.com> diff --git a/src/rtl_test.c b/src/rtl_test.c index f5a56b8..c705e04 100644 --- a/src/rtl_test.c +++ b/src/rtl_test.c @@ -55,6 +55,8 @@ static int ppm_benchmark = 0; static int64_t ppm_count = 0L; static int64_t ppm_total = 0L; +static uint32_t samp_rate = DEFAULT_SAMPLE_RATE; + #ifndef _WIN32 static struct timespec ppm_start; static struct timespec ppm_recent; @@ -108,6 +110,7 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx) { uint32_t i, lost = 0; int64_t ns; + int real_rate; if (uninit) { bcnt = buf[0]; @@ -141,17 +144,23 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx) if (ppm_now.tv_sec - ppm_recent.tv_sec > PPM_DURATION) { ns = 1000000000L * (int64_t)(ppm_now.tv_sec - ppm_recent.tv_sec); ns += (int64_t)(ppm_now.tv_nsec - ppm_recent.tv_nsec); - printf("real sample rate: %i\n", + printf("real sample rate: %i", (int)((1000000000L * ppm_count / 2L) / ns)); - #ifndef __APPLE__ - clock_gettime(CLOCK_REALTIME, &ppm_recent); - #else - gettimeofday(&tv, NULL); - ppm_recent.tv_sec = tv.tv_sec; - ppm_recent.tv_nsec = tv.tv_usec*1000; - #endif + ppm_total += ppm_count / 2L; ppm_count = 0L; + + #ifndef _WIN32 + ns = 1000000000L * (int64_t)(ppm_now.tv_sec - ppm_start.tv_sec); + ns += (int64_t)(ppm_now.tv_nsec - ppm_start.tv_nsec); + real_rate = (int)(ppm_total * 1000000000L / ns); + printf(" cumulative PPM error: %.1f\n", + (1000000.0 * (real_rate - (int)samp_rate)) / samp_rate); + #else + printf("\n"); + #endif + + ppm_recent = ppm_now; } #endif } @@ -213,13 +222,10 @@ int main(int argc, char **argv) int sync_mode = 0; uint8_t *buffer; uint32_t dev_index = 0; - uint32_t samp_rate = DEFAULT_SAMPLE_RATE; uint32_t out_block_size = DEFAULT_BUF_LENGTH; int device_count; int count; int gains[100]; - int real_rate; - int64_t ns; while ((opt = getopt(argc, argv, "d:s:b:tpS::")) != -1) { switch (opt) { @@ -365,15 +371,6 @@ int main(int argc, char **argv) if (do_exit) { fprintf(stderr, "\nUser cancel, exiting...\n"); - if (ppm_benchmark) { -#ifndef _WIN32 - ns = 1000000000L * (int64_t)(ppm_recent.tv_sec - ppm_start.tv_sec); - ns += (int64_t)(ppm_recent.tv_nsec - ppm_start.tv_nsec); - real_rate = (int)(ppm_total * 1000000000L / ns); - printf("Cumulative PPM error: %i\n", - (int)round((double)(1000000 * (real_rate - (int)samp_rate)) / (double)samp_rate)); -#endif - } } else fprintf(stderr, "\nLibrary error %d, exiting...\n", r);

11 years

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rtlsdr not reseting buffers

by Nuno Gonçalves

rtlsdr in async mode is returning buffers full with data from previous calls. I noticed that sometimes the first async callbacks would return TOO QUICKLY so that it would be impossible to have sampled that data. This might be because lib-usb have previous transfers submitted and not cleared? I compiled rtl_test with a small modification that will print the sampling time if it is much lower than expected. BUF_LENGTH is (16 * 16384)=256K, and SAMPLE_RATE is 2048000, so a full buffer should take about 64ms. You can see that in this example the async callback is returned after 7.79ms (and the following one 1.47ms later). So the data must be old. The ns printf nuno@ubuntu:~/Desktop/rtl-sdr/build/src$ ./rtl_test -p Found 1 device(s): 0: ezcap USB 2.0 DVB-T/DAB/FM dongle Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle Found Rafael Micro R820T tuner Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6 Reporting PPM error measurement every 10 seconds... Press ^C after a few minutes. Reading samples in async mode... ERROR ns: 7791886 ERROR ns: 9259301 lost at least 185 bytes real sample rate: 2073369 real sample rate: 2048190 ^CSignal caught, exiting! User cancel, exiting... Cumulative PPM error: -289 The modifications to demonstrate the issue: nuno@ubuntu:~/Desktop/rtl-sdr/src$ git diff diff --git a/src/rtl_test.c b/src/rtl_test.c index f5a56b8..1935bfb 100644 --- a/src/rtl_test.c +++ b/src/rtl_test.c @@ -138,9 +138,11 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t le ppm_now.tv_sec = tv.tv_sec; ppm_now.tv_nsec = tv.tv_usec*1000; #endif - if (ppm_now.tv_sec - ppm_recent.tv_sec > PPM_DURATION) { - ns = 1000000000L * (int64_t)(ppm_now.tv_sec - ppm_recent.tv_sec) - ns += (int64_t)(ppm_now.tv_nsec - ppm_recent.tv_nsec); + ns = 1000000000L * (int64_t)(ppm_now.tv_sec - ppm_recent.tv_sec); + ns += (int64_t)(ppm_now.tv_nsec - ppm_recent.tv_nsec); + if(ns<60000000) + printf("ERROR ns: %9lld\n",ns); + if (ppm_now.tv_sec - ppm_recent.tv_sec > PPM_DURATION) { printf("real sample rate: %i\n", (int)((1000000000L * ppm_count / 2L) / ns)); #ifndef __APPLE__ Nuno

11 years

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Can't get below -46 dB

by Luca Bedogni

Hi I have an Elonics 4000 USB receiver, and I-m trying to do some measurements on the digital television received power in my area. Everything works fine, except that the received power is never lower than -46 dB, even on channel which are not occupied. I was expecting to get values like -120 dB or something similar, instead in my measurements the lowest point in any portion of the spectrum is circa -46 dB. Am I missing something? Thank you Best

11 years, 1 month

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DAB+ free/open encoder: fdk-aac-dabplus

by Benjamin Hagemann

Hello, I read on twitter: Opendigitalradio.org @opendigiradio "A new DAB+ free/open encoder is born ! https://github.com/piratfm/fdk-aac-dabplus …" https://twitter.com/opendigiradio/status/324231787163303936 -- Regards, Benny gpg 0xFC505AB0 jabber benny(a)benny.de sip benny(a)benny.de

11 years, 1 month

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Using the R820T above 1.77 GHz?

by Per Baekgaard

One more (but completely different) topic, hence a separate mail: Has anyone experimented with using the R820T above 1.77 GHz?

11 years, 1 month

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ask help for the format of outcome IQ data

by kainwen

Hello, I use rtl_sdr to collect some data into a bin file(file.bin). As from the wiki, I think it is parsed like this : /fd = open("file.bin","r") ;// // char I[];// // char Q[];// ////loop :// // read(fd, I, 1) ;// // read(fd, Q,1) ;// // endloop// // char *p = Q ;// // loop :// // printf("%f\n", (float*)p);// // p += 4 ;// ////endloop/ But this code can only print 0.00000 I don't know where the error is. Please help me. Thank you.

11 years, 1 month

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Thank you

by Marco Haakmeester

Hi, I believe through this mailaddress I can reach the persons that have written the excellent wiki on the installation of the realtek receiver for it to receive ADS-B signals. I am a vivid Linux 'customer' but not a programmer. Yet, using the instructions I have been able to get a signal on my pc. So thanks for a well written wiki! Best regards, Marco Ps: the most difficult issue to tackle was to find an address for this 'thank you' note ;-)

11 years, 1 month

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R820T "spur prevention" code

by Per Baekgaard

List, As a new member here, only recently having acquired a few SDR units, I am not sure if this is the right place to post the following. If not, feel free to advice me of a better way (for reference, I've tried to mail a few of the key people here already directly, but I guess that was not the correct way to approach it). R820T tuning problems ============== As far as I can tell, the "correct" way to tune a RTL SDR device is to call rtlsdr_set_center_freq, which in turn invokes the set_freq function of the driver (mapped to r820t_set_freq which further calls r820t_SetRfFreqHz in case of the R820T). This may not always result in the desired frequency being tuned to. In some cases, such as with the current tuner_r820t.c driver, it can lead to rather large "errors" *). For instance, trying to tune to 144.000 MHz works as intended -- but tuning to anything in the range 144.002 to 144.058 will lead to center frequency of 144.030 MHz, or in other words an error as large of 28 kHz. [If you apply a PPM value other than 0, the exact range will be a little different.] I've also seen cases where use of the "kalibrate" program to locate GSM channels has resulted in one actual GSM channel being detected on 3 adjacent channels, 2 of which are incorrect -- and the calculated frequency deviation is also often wrong on some channels. For GSM channels and other frequencies above 885 MHz, the tuning "error" can be as much +/- ~225 kHz. Now, the way for an application to verify the resulting tuning would be to call the rtlsdr_get_center_freq. However, in the current implementation, this will return the requested tuning (adjusted with any calculated offsets set in the librtlsdr.c driver -- which is not applicable for the R820T) and not the actual tuning. Further, I've checked a couple of GUI programs on how they use the rtl library. One (linrad) only calls the rtlsdr_set_center_freq function and newer checks the resulting tuning. Another (gqrx via the osmo library) does a similar thing, but has a note "FIXME: Read back frequency?" comment. Also, the kalibrate suite does not check for the actual tuned frequency either. So all of these applications will report an incorrect frequency of the spectrum, and the error depends on what center frequency you may have requested. So -- unless I have overlooked something, which could be entirely possible -- the current R820T driver sometimes detunes the requested center frequency and the applications using it are not checking for this. And if they had wanted to do so, they have no means to with the current codebase. Proposed "fix" ======== I understand the R820T driver is messy anyway and that its origin has caused it to be what it is. The problem above is caused by a few lines of code in tuner_r820t.c around line 1460, that does "spur prevention". The idea is that if the resulting VCO frequency is too close to a harmonics of the xtal/2 frequency, the VCO is detuned to run exactly on top of the harmonics, to reduce any spurs within a (450/N) kHz bandwith, where N is the MixDiv, i.e. the divisor used to derive the center frequency from the VCO that runs between 1.77 and 3.54 GHz. This probably makes a lot of sense for applications where the exact tuning is not too important. Likely when using the stick for DVB-T as originally intended, the later stages will compensate for the detuning and just benefit from the reduced amount of spurs. But for our use, it might make less sense and I guess most of the other drivers have not implemented something like this anyway? I can think of the following ways to fix this issue: 1) Disable the code that does the detuning (either temporarily (#if 0/#endif) or by some setup parameter so that an application can specifically ask for the "detune" behaviour). This will possibly introduce additional spur on the R820T, in the presence of strong "near-center frequency" signals, but will fix the problem for existing SDR applications. In case of an optional "setup" parameter, proper handling of the detuning and reporting back to the calling application has to be made available, and those applications then eventually need to implement some way of handling it. 2) Merge with the possibly somewhat similar "offset" tuning method implemented for some other devices -- although I'm not sure exactly how that is intended to work and if it truly is compatible with the R820T method. 3) Keep the code as is, but "tweak" the sampling in the 2832 device to compensate for the offset tuning. So in other words, instead of assuming the nominal IF of 3.57 MHz, tune to an offset IF. This will obviously skew the BW and may not work for smaller sampling rates, where the offset could actually be larger than what the sampling rate allows... I would propose to simply disable the code for now (and I'm happy to submit a small patch), as the detuning currently appears to introduce more problems than it solves. A 2nd step would then be to add a proper report-back abstraction/functionality to all drivers and make the librtlsdr.c code fully aware of the detuning and allow it to be reported back to the caller, and then ask the application developers to start using the get_center_freq calls -- at least if they have asked for "enable_spur_prevention" or something similar. Thanks for any comments/advice on the above, -- Per.

11 years, 1 month

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gr-osmosdr build problem

by Wojciech Kazubski

Hello! Fo some time I am unable to build gr-osmosdr with enabled documentation. ... cmake -DCMAKE_INSTALL_PREFIX=/usr -DENABLE_DOXYGEN=1 ../ make -j2 ... The build fails with the following error: ... [ 151s] [ 26%] Built target doxygen_target [ 151s] Scanning dependencies of target osmosdr_swig_swig_doc [ 151s] [ 30%] Generating doxygen xml for osmosdr_swig_doc docs [ 151s] /bin/sh: osmosdr_swig_doc_swig_docs/Doxyfile: Permission denied [ 151s] make[2]: *** [swig/osmosdr_swig_doc_swig_docs/xml/index.xml] Error 126 [ 151s] make[1]: *** [swig/CMakeFiles/osmosdr_swig_swig_doc.dir/all] Error 2 [ 151s] make[1]: *** Waiting for unfinished jobs.... ... This happen after this commit: http://cgit.osmocom.org/gr-osmosdr/commit/?id=dc28f6c4c874e182557c8cb9fe8a0… (the last one from Feb 16 2013) For me, it looks like an attempt to run Doxyfile directly and not process it by doxygen. Wojciech Kazubski

11 years, 1 month

2
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RTL offset with kalibrate-rtl

by Nuno Gonçalves

I have a stick with the R820T Tunner. Using SDR# and SDR-Radio V2, and tunning to FRS and Airband transmitters I determined that my offset is consistent to 54-63 PPM. On the other hand kalibrate-rtl reports my offset to be about -30PPM, also consistently accross several tests. Is there possibly any difference from 100 (Airband), 400 (FRS) and 900ish (GSM) Mhz? I am at Portugal, so the network is probably a GSM900 and also I don't get something as NOAA narrow channels to figure this out. GSM-900: chan: 10 (937.0MHz + 27.986kHz) power: 29372.03 chan: 30 (941.0MHz + 26.850kHz) power: 197782.82 chan: 50 (945.0MHz + 26.645kHz) power: 86521.18 chan: 62 (947.4MHz + 27.109kHz) power: 29501.15 chan: 74 (949.8MHz + 26.605kHz) power: 56078.03 chan: 107 (956.4MHz + 26.442kHz) power: 57536.25 chan: 112 (957.4MHz + 25.319kHz) power: 31011.95 chan: 121 (959.2MHz + 25.145kHz) power: 87002.34 E-GSM-900: chan: 10 (937.0MHz + 27.514kHz) power: 27631.40 chan: 30 (941.0MHz + 26.395kHz) power: 211497.68 chan: 50 (945.0MHz + 26.209kHz) power: 88871.46 chan: 62 (947.4MHz + 26.629kHz) power: 27770.99 chan: 74 (949.8MHz + 26.181kHz) power: 56274.60 chan: 107 (956.4MHz + 25.984kHz) power: 47437.43 chan: 112 (957.4MHz + 24.878kHz) power: 25791.29 chan: 121 (959.2MHz + 24.765kHz) power: 98473.19 What can be going on here? Also, what is the reason for the dropped samples when sampling over 2.8MS/s? Is it a RTL2832 issue or something related to the USB driver? Regards, Nuno

11 years, 1 month

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[PATCH] rtl-sdr: add support for lib64 (e.g. Fedora)

by Jaroslav Skarvada

From: "Jaroslav Škarvada" <jskarvad(a)redhat.com> To: laforge(a)gnumonks.org Cc: "Jaroslav Škarvada" <jskarvad(a)redhat.com> Sent: Thursday, April 4, 2013 3:36:18 PM Subject: [PATCH] rtl-sdr: add support for lib64 (e.g. Fedora) Another possibility is to use the GrPlatform.cmake module. Signed-off-by: Jaroslav Škarvada <jskarvad(a)redhat.com> --- CMakeLists.txt | 8 ++++++-- src/CMakeLists.txt | 4 ++-- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/CMakeLists.txt b/CMakeLists.txt index f3ef31e..b113311 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -33,6 +33,10 @@ set(CMAKE_BUILD_TYPE ${CMAKE_BUILD_TYPE} CACHE STRING "") list(APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/Modules) +if(NOT LIB_INSTALL_DIR) + set(LIB_INSTALL_DIR lib) +endif() + ######################################################################## # Compiler specific setup ######################################################################## @@ -130,7 +134,7 @@ ENDIF(CMAKE_CROSSCOMPILING) set(prefix ${CMAKE_INSTALL_PREFIX}) set(exec_prefix \${prefix}) -set(libdir \${exec_prefix}/lib) +set(libdir \${exec_prefix}/${LIB_INSTALL_DIR}) set(includedir \${prefix}/include) CONFIGURE_FILE( @@ -140,5 +144,5 @@ CONFIGURE_FILE( INSTALL( FILES ${CMAKE_CURRENT_BINARY_DIR}/librtlsdr.pc - DESTINATION lib/pkgconfig + DESTINATION ${LIB_INSTALL_DIR}/pkgconfig ) diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt index 6b23395..4b91a4b 100644 --- a/src/CMakeLists.txt +++ b/src/CMakeLists.txt @@ -126,7 +126,7 @@ endif() # Install built library files & utilities ######################################################################## install(TARGETS ${INSTALL_TARGETS} - LIBRARY DESTINATION lib${LIB_SUFFIX} # .so/.dylib file - ARCHIVE DESTINATION lib${LIB_SUFFIX} # .lib file + LIBRARY DESTINATION ${LIB_INSTALL_DIR} # .so/.dylib file + ARCHIVE DESTINATION ${LIB_INSTALL_DIR} # .lib file RUNTIME DESTINATION bin # .dll file ) -- 1.8.1.4

11 years, 1 month

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Re: osmocom-sdr Digest, Vol 17, Issue 3

by Peter Stuge

Thomas Stowe wrote: > Great, admin failure on the list. I'm unsubscribing, fuck this shit. A shame to see such a strong contributor leave. //Peter

11 years, 1 month

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feedback: Terratec ran - T Stick+

by Thomas Osterried

Hello, my feedback to http://sdr.osmocom.org/trac/wiki/rtl-sdr and the list of working devices: I buyed a "Terratec ran - T Stick+". It's working. lsusb shows the following IDs: Bus 005 Device 033: ID 0ccd:00d7 TerraTec Electronic GmbH It's a DVB / DAB/DAB+ stick (what ever this means - it's all about SDR ;). Buyed it at conrad for < 20 Eur. I found the device reading http://lehwalder.wordpress.com/2012/12/31/sdr-software-defined-radio/ It's already mentioned in http://www.randomprojects.org/wiki/Software_defined_radio#Terratec_ran_T_St… Thank you for your good work.. - Thomas

11 years, 1 month

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[PATCH 1/2] doxygen package needs to be detetected before the doxygen is used

by Jaroslav Škarvada

Without this patch the DOXYGEN_EXECUTABLE is set too late which results in build failure when processing swig directory (with ENABLE_DOXYGEN). Signed-off-by: Jaroslav Škarvada <jskarvad(a)redhat.com> --- CMakeLists.txt | 1 + docs/CMakeLists.txt | 5 ----- 2 files changed, 1 insertion(+), 5 deletions(-) diff --git a/CMakeLists.txt b/CMakeLists.txt index a9334c8..a1af563 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -116,6 +116,7 @@ find_package(GnuradioFCD) find_package(LibOsmoSDR) find_package(LibRTLSDR) find_package(LibMiriSDR) +find_package(Doxygen) if(NOT GRUEL_FOUND) message(FATAL_ERROR "Gruel required to compile osmosdr") diff --git a/docs/CMakeLists.txt b/docs/CMakeLists.txt index f16fbf6..446b86a 100644 --- a/docs/CMakeLists.txt +++ b/docs/CMakeLists.txt @@ -18,11 +18,6 @@ # Boston, MA 02110-1301, USA. ######################################################################## -# Setup dependencies -######################################################################## -find_package(Doxygen) - -######################################################################## # Begin conditional configuration ######################################################################## if(ENABLE_DOXYGEN) -- 1.8.1.4

11 years, 1 month

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osmocom-sdr April 2013