osmocom-sdr

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917 discussions

E4000 undocumented registers?
by Adam Nielsen 11 Nov '12

11 Nov '12

Hi all, I've been looking at the E4000 tuner code and I have a couple of questions that aren't answered in the datasheet. I'm hoping someone here might have some insight. In the Elonics-supplied code[1] when setting the frequency (around line 1339), they always write a 1 into register 0x07 (Synth1), which is the "PLL locked" register. Does this affect anything? The datasheet says it's read only and librtlsdr only ever reads this value, it never writes to it. Then, beginning at 82.9MHz and continuing at every multiple of 28.8MHz above this, the first 7MHz is tuned differently, but the rest of the 21.8MHz in that "channel" is set normally. This stops between 233.9MHz and 485.6MHz, then resumes again at 8MHz increments instead of 7MHz up until 868MHz. When tuned differently, register 0x05 (Input clock) gets set to 3, which isn't listed in the datasheet (and also says 'do not write to this register'). Mostly (but not always) when this happens (i.e. first 7-8MHz of the channel), register 0x07 bits 3-4 are also set to various arbitrary values. The datasheet says 0 means "16-32MHz input clock freq range" but this code writes 1 and 2 into this field as well. It seems to write approximately these values: 1 up to 89.9MHz 0 up to 118.7MHz 1 up to 205.1MHz 2 up to 233.9MHz 0 up to 551.2MHz 1 up to 752.8MHz 2 up to 868MHz 0 after 868MHz After the first 7-8MHz the rest of the 28.8MHz channel has the default 0 value set. Does anyone know what these values control? As a side note, register 0x08 (Synth2) appears to do something even though it's listed as reserved. By setting particular bits I can get the rtl_test program to not lock on to any frequency, but oddly enough rtl_fm still works fine. I'm not sure what to make of this yet. I don't suppose this register is documented anywhere else? I'm just wondering whether the datasheets supplied by Elonics are different to the one that is now public. Thanks, Adam. [1]: One of many copies is at https://github.com/mbarbon/rtl2832/blob/master/tuners/tuner_e4000.c

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removing the L-band gap on E4000
by Jacek Lipkowski 08 Nov '12

08 Nov '12

Hello I've tried to remove the L-band gap on my E4000 tuner by changing the divisors. Please see the patch below. I don't have a signal source to test today, so i'm not sure if it works, but the pll locks. I will try to test tomorrow. Without my hack: E4K L-band gap: 1093 to 1233 MHz With my hack: sq5bpf@dellix:~/gnuradio/rtl-sdr/src$ ./rtl_test -t 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 Elonics E4000 tuner Supported gain values (14): -1.0 1.5 4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 24.0 29.0 34.0 42.0 Benchmarking E4000 PLL... [E4K] PLL not locked for 51000000 Hz! [E4K] PLL not locked for 2186000000 Hz! E4K range: 52 to 2185 MHz E4K L-band gap: 0 to 0 MHz Regards Jacek / SQ5BPF --- tuner_e4k.c.orig 2012-11-08 22:08:07.000000000 +0100 +++ tuner_e4k.c 2012-11-08 23:01:05.000000000 +0100 @@ -35,6 +35,7 @@ /* If this is defined, the limits are somewhat relaxed compared to what the * vendor claims is possible */ #define OUT_OF_SPEC +#define HACKED_DIVISORS #define MHZ(x) ((x)*1000*1000) #define KHZ(x) ((x)*1000) @@ -357,7 +358,14 @@ {KHZ(350000), (1 << 3) | 1, 8}, {KHZ(432000), (0 << 3) | 3, 8}, {KHZ(667000), (0 << 3) | 2, 6}, - {KHZ(1200000), (0 << 3) | 1, 4} +#ifdef HACKED_DIVISORS +/* the original settings seem to be ripped from some Elonics driver, + * however changing them a bit removes the L-band gap + * change this to a bit more then the end of your L-band gap --sq5bpf */ + {KHZ(1270000), (0 << 3) | 1, 3} +#else + {KHZ(1200000), (0 << 3) | 1, 4} +#endif }; static int is_fvco_valid(uint32_t fvco_z)

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RTL-SDR with MSI DIGIVOX Micro HD support
by Höss Lajos 07 Nov '12

07 Nov '12

Hi, Good news with MSI DIGIVOX Micro HD (1d19:1104) DVB-T tuner. Now the tuner working. Succesfully received analague UHF TV sound channel 80 kilometer distance from transmitter, taxi driver (164 Mhz) and one frequency from 70cm radio amateur band. The tuner is FCI FC2580 from debug message. I see on http://sdr.osmocom.org/trac/wiki/rtl-sdr great new info for this tuner 146 - 308 MHz and 438 - 924 MHz (gap in between). Not have any wideband generator for check this, but for example with strong local FM radio station 87.5-108MHz tunable, but received only noise. I think the frequency range possibly same. All rtl-sdr DVB-T tuner with fc2850 has a same frequency range? I interesting for not working frequiency, working frequiency or working freq. but poor receiver quality, or any gap. I interesting also for 2 meter radio amateur band, only max. 2 MHz lower. 144-146MHZ only noise received, i not know my antenna bad, or this is not possible. mngc

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Small thinko in testing for clock_gettime
by Pete Zaitcev 07 Nov '12

07 Nov '12

This appears to be not tested with autoconf (cmake works). The assignment to $LIBS changes nothing, which cannot possibly be the intent. --- cc-ing to original patch author and sign-off diff --git a/configure.ac b/configure.ac index 1b94701..c760787 100644 --- a/configure.ac +++ b/configure.ac @@ -40,7 +40,7 @@ dnl libmath (for rtl_fm) AC_CHECK_LIB(m, atan2, [LIBS="$LIBS -lm"]) dnl librealtime (for rtl_test) -AC_CHECK_LIB(rt, clock_gettime, [LIBS="$LIBS"]) +AC_CHECK_LIB(rt, clock_gettime, [LIBS="$LIBS -lrt"]) # The following test is taken from WebKit's webkit.m4 saved_CFLAGS="$CFLAGS"

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Latest Ubuntu update
by James Peroulas 04 Nov '12

04 Nov '12

I'm running Ubuntu 12.04 and after installing all the latest security and recommended updates, I'm having problems with the rtlsdr library relating to rtlsdr_cancel_async. For example: rtl_sdr -f 739000000 -n 1000000 cap.dat The above will successfully capture exactly 1M samples into cap.dat, but it will not exit after the capture is finished. I have to break out with ctrl-c. Anybody having similar problems? Hoping I don't have to re-install Ubuntu... :( James -- *Integrity is a binary state - **either you have it or you don’t.* - John Doerr

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4Mbps hack wiring & 48 MHz spurs
by Sylvain Munaut 01 Nov '12

01 Nov '12

Just fyi, here's how I did the 4msps wiring hack : http://i.imgur.com/TODkU.png Basically use resistors (I used 270R which is a bit high ,between 20 and 10R would bwe better) on the back side on the PCB. I initially started with wire jumpers on the pins, then moved to resisors on the top but that created a huge loop area with the ground return (there is no gnd on those connection) which was heavily radiating. Mounting on the back like that dropped it significantely for me (especially on baseband), but you still clearly see it. I think the FPGA drive strength on the data pins is still way too high and should be reduced. Maybe using spread spectrum on the MCI would be another idea ? Cheers, Sylvain

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Beginner question about rtlsdr
by Jared Clements 27 Oct '12

27 Oct '12

Hi list, hi Michel, I'm new here, but have been working on the same solution as you are, but for an Amsat all sky tracking receiver. First, let me point you to the signal processing textbook I've been working my way through: dspguide.com. It can be a bit verbose for a textbook, but that's been to my advantage several times. I've run into two clear obstacles trying to build an interferometric array. Both have to do with clock synchronization. First is clock drift. No matter how expensive the crystal, or precise the temperature control, two clocks are going to drift with respect to each other. I'm planning on solving this one by pulling the crystal off the dongles and replacing it with a clock input that I'll pipe from one single clock/crystal out to each dongle. I'm assuming that I'll have to use equal length cables to keep my timing correct. The second problem is synchronizing the separate data streams so I know which samples were taken at the exact same time. This one is a bit trickier, and I don't think there's a hardware solution for it. Most multichannel data acquisition systems have a trigger system to solve this, where all the channels get initialized but don't start to capture until the trigger is received. Unfortunately I don't think there's a trigger input pin anywhere in our dongles. There is another way, and that's find a known RF signal that we can use for synchronization. GPS would be ideal, because there's explicit solutions for time offsets/drift that's referenced to atomic clocks. We could record 5 minutes or so on the L1 band before an observation, then mid-capture tune to our frequency of interest...assuming we can shift the e4k chip without interupting the RTL2832 in it's capture sequence. Does anyone here know if this is possible? Shift the tuner without interupting the capture? This does require a wide band antenna, best options seem to be spiral and conical spiral. There's probably other options, like an active gps patch antenna that's duplexed in with a frequency specific duplexer, but I'm not much of an rf guy and I like the simplicity of the single wide band antenna. I've also been looking at options for building out an array, I've seen reports that a good LNA can get 20dB in SNR, but a wideband preamp runs $70 on minicircuits website. Plus the cost of a bias T and a clean power supply. And I'm not sure that I understand all the built-in options for amplification and filtering yet. That design trade is still pretty fuzzy. It might be more cost effective to just buy more dongles and get better SNR through summing their outputs. More research required!

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Re: Beginner question about rtlsdr (Jared Clements)
by James Peroulas 25 Oct '12

25 Oct '12

> There is another way, and that's find a known RF signal that we can use for > synchronization. GPS would be ideal, because there's explicit solutions for > time offsets/drift that's referenced to atomic clocks. We could record 5 > minutes or so on the L1 band before an observation, then mid-capture tune > to our frequency of interest...assuming we can shift the e4k chip without > interupting the RTL2832 in it's capture sequence. > I'm not very familiar with your application, but you may also have to do sub-sample time offset estimation and compensation. Even though all of the dongles are running at exactly the same sampling *rate*, their sampling * instants* will likely be different. This is despite the fact that you used the same length of cable to feed the clock to all the dongles. For example, if you want a 2.88MHz sampling rate, this will involve dividing the 28.8MHz input by a factor of 10. One dongle might use edge numbers 0, 10, 20, 30, ... of the source clock to produce the 2.88 MHz clock and another might used edge numbers 3, 13, 23, 33, .... Their sampling frequencies will be exactly the same, but the sampling instant will be different. > Does anyone here know if this is possible? Shift the tuner without > interupting the capture? > I can confirm that you can do this since this is what I did in my LTE cell scanner to improve search speed. I configured the A/D rate once, and then I just kept changing the LO frequency. The thing is that once you change the LO frequency, the phase rotation of the received signal will change randomly for all the dongles. So, during the calibration phase, you might find that dongle 1 needs a time correction of t1 and phase correction of p1 to get its signal to align with the signal from dongle 2. After you change the LO, dongle 1 will still need the same time correction (t1), but you wont know what phase to use. Perhaps phase alignment isn't necessary for your application? BR, James -- *Integrity is a binary state - **either you have it or you don’t.* - John Doerr

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Beginner question about rtlsdr
by Michel Pelletier 22 Oct '12

22 Oct '12

Hello everyone, I hope this is an appropriate forum for a beginner question about using an E4000 dongle. I'm an amateur astronomer, and lately I've been wanting to get into amateur radio astronomy. The rtlsdr seems like a really cheap way to get involved. It can tune many interesting frequencies, in particular channel 37 around 608-614 Mhz. I am a Python programmer by trade so I am using roger-'s amazing pyrtlsdr library which is great, I can read samples from the device and they get returned as numpy arrays. The scipy.signal package allows me to correctly decimate the signal and I am working on a simple graphing program to graph signal levels in realtime, by hour, by day, and by week. I hope to basically reproduce the Jansky experiment that started the entire science of radio astronomy: http://en.wikipedia.org/wiki/Karl_Guthe_Jansky I have a question though about how to use the dongle that I can't quite figure out. roger-'s demo_waterfall program, for example, sets the default sample_rate to 1.4e6, but then on each scan only calls read_samples(2**16). The demo displays the entire megahertz of bandwidth, so I'm a bit confused as to how the 64K samples map onto the 1M samples of the device. It doesn't seem to make sense taht the device only returns the first 64K samples. Can anyone clue in a total beginner on the sample rate and reading samples from the device correlate? Thank you! -Michel

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RTL-SDR with MSI DIGIVOX Micro HD suppot
by Höss Lajos 21 Oct '12

21 Oct '12

Hi, I have USB DVB-T stick. Possibly add suport for rtl-sdr? Name: MSI DIGIVOX Micro HD (Dexatek clone?, i see black diamond design, same as Dexatek, and i found 1d19 = Dexatek) USB ID (from linux and windows): 1d19:1104 Working (very old) driver for linux rtl2832u, my linux very old, i cannot complile the current rtl-sdr because libusb, etc. too old. I will ugrade to new linux, but requies long time. I not know how to identify the tuner, but from dmesg i think this device use rtl2832 chipset + FC2580 tuner I try with nightly build sdl-sharp, and the latest http://sdr.osmocom.org/trac/attachment/wiki/rtl-sdr/RelWithDebInfo.zip on windows, no succes. mngc

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