osmocom-sdr

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917 discussions

Re: ACARS decoder using rtl-sdr
by Pawel Janowski 19 Jul '13

19 Jul '13

Hello its great idea ! I think the next step (small for man big form mankind) should be decoding (based on rtl_fm) APRS messages and putting into APRS-IS Servers ! with regards Pawel, SQ7MRU http://sq7mru.blogspot.com/

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Re: ACARS decoder using rtl-sdr
by Adam Nielsen 18 Jul '13

18 Jul '13

> Hi, > > The grab connection doesn't work :( > > 73, Murat TA1DB If you're running a recent version of Linux, it will load DVB drivers so you can watch TV with the device. You'll have to unload these to make the device available for use: sudo rmmod dvb_usb_rtl28xxu rtl2832 e4000 (assuming an e4000 device, not sure what module to unload for other tuners, lsmod will tell you.) Cheers, Adam.

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Possible bug in device removal detection code in librtlsdr.c
by Alexey Kruglov 16 Jul '13

16 Jul '13

Hi. Device removal detection code in _libusb_callback in librtlsdr.c may be buggy. Every time we get any status other than LIBUSB_TRANSFER_COMPLETED (including LIBUSB_TRANSFER_ERROR) the code doesn't resubmit current buffer, and we get the real number of working buffers decreased by one. If that number goes down to 0, rtlsdr_read_async() will hang. Linux version tries to control it by counting the number of LIBUSB_TRANSFER_ERROR buffers that came in row in dev->xfer_errors. But if we already have _one_ failed buffer during the whole transfer up to the moment, that counter will never reach dev->xfer_buf_num. So it seems more straightforward to 1. count the failed buffers and rtlsdr_cancel_async() when it reaches 0 or some sensible threshold, and 2. maybe resubmit some kinds of the failed buffers other than LIBUSB_TRANSFER_COMPLETED, if it makes sense. I am not a libusb guru and it's not well documented in this part, so I am not sure about my second point. Hoping some librtlsdr developers will appear on this list. -- GPG fp: 6DFA 1186 7576 DE60 6CCB EB39 AD81 1733 EEBB 970A

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Delay after rtlsdr_cancel_async
by Alexey Kruglov 16 Jul '13

16 Jul '13

Hi. I noticed there is a 1 second delay in librtlsdr between calling rtlsdr_cancel_async and releasing from rtlsdr_read_async. I'm writing a radio scanner and this delay limits scanning speed considerably. I tracked the delay down to this piece of code in librtlsdr.c: while (RTLSDR_INACTIVE != dev->async_status) { r = libusb_handle_events_timeout(dev->ctx, &tv); [...] if (RTLSDR_CANCELING == dev->async_status) { next_status = RTLSDR_INACTIVE; [...] if (dev->dev_lost || RTLSDR_INACTIVE == next_status) { >>>> libusb_handle_events_timeout(dev->ctx, &tv); break; } The marked line is almost always(?) invoked when all the events are already processed, hence it blocks for tv = 1 second. In fact I don't understand what this `if' is supposed to do at all. I tried to modify this line by changing the delay to 0 making it a non-blocking call (leaving the timeout of 1 sec for the former libusb_handle_events_timeout call). This worked with my project and the 1 second delay disappeared. So, I suppose, it's better to either a) remove the whole `if' or b) make the latter libusb_handle_events_timeout non-blocking as I did. I checked that b) works for me, and didn't test a) yet. The question is: what that `if (dev->dev_lost ...' is supposed to do? And the two possible fixes for 1 second delay bug depending on the answer are (diffs): === 1630a1631 > struct timeval tv_nb = { 0, 0 }; 1696c1697 < libusb_handle_events_timeout(dev->ctx, &tv); --- > libusb_handle_events_timeout(dev->ctx, &tv_nb); === === 1694,1698d1693 < < if (dev->dev_lost || RTLSDR_INACTIVE == next_status) { < libusb_handle_events_timeout(dev->ctx, &tv); < break; < } === -- GPG fp: 6DFA 1186 7576 DE60 6CCB EB39 AD81 1733 EEBB 970A

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Anybody running gr-osmosdr or gr-baz under Windows?
by Murat Toloğlu 09 Jul '13

09 Jul '13

Hi All, After more than 2 weeks of endless trials to build, install and run gr-osmosdr and/or gr-baz in Windows 7 to have an RTL2832 source in GNU Radio - GRC without success I really wander if anybody exists and running these programs under Windows? Do you know anybody who succeeded to build and install gr-osmosdr and/or gr-baz in Windows? Regards, Mu

1 0

minimum sample rates?
by David Jacobowitz 27 Jun '13

27 Jun '13

I'm trying to write some code that uses a Raspberry Pi not just to capture the samples, but also to do the DSP. The signal I'm working (aviation VOR) is narrow and the DSP is not too hard-core, but it'll be easier if I can sample at a lower rate. Though rtlsdr_set_sample_rate returns no errors and rtlsdr_get_sample_rate returns the same value I gave it (or quite close), it does not appear to be working. I had been working at 250ksps but wanted to try 125ksps or even 62500sps, but none of those seem to work. Is this just a limitation of the hardware? I have a NooElec RTL2832 / R820T device if that matters. Regards, Dave J

3 5

a new and more mature SDR Dongle
by Jay Salsburg 26 Jun '13

26 Jun '13

Have any of you seen this? It appears as though we have a new and more mature SDR Dongle available. http://www.mirics.com/sites/default/files/MSi3101_new.pdf <http://www.mirics.com/node/6> http://www.mirics.com/node/6 Thanks goes out to Francesco for supplying the links to this site

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realtek rumor
by Mathias Coinchon 26 Jun '13

26 Jun '13

Hello, I heard a rumor from someone from industry that Realtek RTL2832u chip would soon be phased out and replaced by another chip (with lower sensitivity according to my contact). Does anybody has more information about this ? Regards Mathias

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Enhancement Request
by jdowjunkmail＠earthlink.net 24 Jun '13

24 Jun '13

Background: Suppose you have four dongles. (That's easy for me. I do.) Suppose they all identify as one of two types. (Three of one and one of the other.) Suppose you want to load a specific dongle when you start the program. And you don't want it to matter if you move the dongles around. How do I do that? Welllll, I hacked. Unfortunately rtlsdr.dll does not allow me to do this even if I alter the serial numbers, at least not the way I want. There is a fly in the rtlsdr ointment when fishing for the USB strings for Manufacturer ID, product ID, and serial number. You must formally open the device to read these values. The dongle can only be opened by one opener at a time. Unfortunately SDRSharp is laid out inside such that it searches for dongles whenever you open Config. And any time you open Config you also have a dongle open. So far this is not too bad a problem. If there's a dongle I cannot poll for strings, that's the one I have open. Er, not so fast, Joanne. What if you have two or more copies open? There will be more than one dongle you cannot poll. I had to figure out how I could identify the dongle I have open even if I move dongles. So I dug in and found some things libusb.dll can do. The chief one is get the USB path for the dongle. And it can do that without actually opening the dongle. Now when filling out the dialog if I cannot read strings for a dongle I get the dongle's path from the device list used and by cheating on the device handle rtlsdr.dll hands out for opened dongles I extracted information I needed to get the path that way. If they compare it's obviously my dongle. If they do not compare it's another dongle that is already opened so I don't show it in the list. Request: Please implement two new entry points which expose the libusb_get_port_path functionality, one by index (same as for strings) and one for rtlsdr handle which I finessed to prove the technique above. The libusb_get_device function will take the device handle and spit out the device list entry that matches the handle. Thanks for considering this. {^_^} Joanne/W6MKU

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rtl_fm question
by Favati 16 Jun '13

16 Jun '13

Hi! I'm modifying rtl_fm to change frequency and demod based on the date/time. For the frequency i've no problem, but changing the modulation from wfm to any other gives me no outout at all. Which is the best approach to change the demod type in realtime? (whitout shutting down rtl_fm of course!) Many thanks!

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