osmocom-sdr

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910 discussions

[rtl-sdr] store frequency correction in eeprom?
by Benedikt Heinz 31 May '13

31 May '13

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

4 3

[PATCH 0/2] Store frequency calibration in EEPROM
by Andreas Seltenreich 29 May '13

29 May '13

Hi, I modified my copy of rtl-sdr to be able to store frequency calibration on the sticks themselves. Maybe this change is generally useful? Thanks, andreas Andreas Seltenreich (2): rtl_eeprom: Add -x to store exact xtal frequency in Hz. lib: Try reading xtal calibration from EEPROM. src/librtlsdr.c | 21 +++++++++++++++++++-- src/rtl_eeprom.c | 17 ++++++++++++++++- 2 files changed, 35 insertions(+), 3 deletions(-) -- 1.7.10.4

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[PATCH 2/2] lib: Try reading xtal calibration from EEPROM.
by Andreas Seltenreich 29 May '13

29 May '13

Interpret last four bytes of EEPROM as value in Hz using network byte order and use it as default if it is between MIN_RTL_XTAL_FREQ and MAX_RTL_XTAL_FREQ. --- src/librtlsdr.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 2f5d90a..c986018 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -25,6 +25,9 @@ #ifndef _WIN32 #include <unistd.h> #define min(a, b) (((a) < (b)) ? (a) : (b)) +#include <arpa/inet.h> +#else +#include <WinSock2.h> #endif #include <libusb.h> @@ -279,6 +282,7 @@ static rtlsdr_dongle_t known_devices[] = { #define BULK_TIMEOUT 0 #define EEPROM_ADDR 0xa0 +#define EEPROM_SIZE 256 enum usb_reg { USB_SYSCTL = 0x2000, @@ -1365,14 +1369,27 @@ int rtlsdr_open(rtlsdr_dev_t **out_dev, uint32_t index) goto err; } - dev->rtl_xtal = DEF_RTL_XTAL_FREQ; - /* perform a dummy write, if it fails, reset the device */ if (rtlsdr_write_reg(dev, USBB, USB_SYSCTL, 0x09, 1) < 0) { fprintf(stderr, "Resetting device...\n"); libusb_reset_device(dev->devh); } + dev->rtl_xtal = DEF_RTL_XTAL_FREQ; + + /* Allow for the last four bytes of the EEPROM to contain a + calibration frequency. */ + { + uint32_t rtl_freq; + + if (0 < rtlsdr_read_eeprom(dev, (void *)&rtl_freq, EEPROM_SIZE-4, 4)) + rtl_freq = ntohl(rtl_freq); + if (rtl_freq >= MIN_RTL_XTAL_FREQ && rtl_freq <= MAX_RTL_XTAL_FREQ) { + fprintf(stderr, "Found valid XTAL calibration in EEPROM: %u Hz\n", + dev->rtl_xtal = rtl_freq); + } + } + rtlsdr_init_baseband(dev); dev->dev_lost = 0; -- 1.7.10.4

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[PATCH 1/2] rtl_eeprom: Add -x to store exact xtal frequency in Hz.
by Andreas Seltenreich 29 May '13

29 May '13

Stored in the last four bytes of the eeprom in network byte order. --- src/rtl_eeprom.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/src/rtl_eeprom.c b/src/rtl_eeprom.c index 35191de..51024d6 100644 --- a/src/rtl_eeprom.c +++ b/src/rtl_eeprom.c @@ -23,8 +23,10 @@ #ifndef _WIN32 #include <unistd.h> +#include <arpa/inet.h> #else #include <Windows.h> +#include <WinSock2.h> #include "getopt/getopt.h" #endif @@ -84,6 +86,7 @@ void usage(void) "\t[ terratec_plus\tTerratec T Stick+ (DVB-T/DAB)]\n" "\t[-w <filename> write dumped file to device]\n" "\t[-r <filename> dump EEPROM to file]\n" + "\t[-x <Hz> store calibrated XTAL frequency]\n" "\t[-h display this help text]\n" "\nUse on your own risk, especially -w!\n"); exit(1); @@ -262,9 +265,10 @@ int main(int argc, char **argv) int default_config = 0; int change = 0; int ir_endpoint = 0; + uint32_t xtal_freq = 0; char ch; - while ((opt = getopt(argc, argv, "d:m:p:s:i:g:w:r:h?")) != -1) { + while ((opt = getopt(argc, argv, "d:m:p:s:i:g:w:r:x:h?")) != -1) { switch (opt) { case 'd': dev_index = atoi(optarg); @@ -306,6 +310,9 @@ int main(int argc, char **argv) case 'r': filename = optarg; break; + case 'x': + xtal_freq = htonl(atol(optarg)); + break; default: usage(); break; @@ -347,6 +354,14 @@ int main(int argc, char **argv) if (r < 0) return -1; + if(xtal_freq) { + r = rtlsdr_write_eeprom(dev, (void*)&xtal_freq, EEPROM_SIZE-4, 4); + if (r < 0) + fprintf(stderr, "Error while writing XTAL frequency to EEPROM: %i\n", r); + else + fprintf(stderr, "XTAL frequency successfully written.\n"); + } + fprintf(stderr, "Current configuration:\n"); parse_eeprom_to_conf(&conf, buf); dump_config(&conf); -- 1.7.10.4

1 0

Updated gr-osmosdr for GNU Radio 3.7
by Tom Rondeau 26 May '13

26 May '13

Not sure if anyone else had worked on this, but I couldn't find anything. I updated gr-osmosdr to work with GNU Radio 3.7 (currently the next branch). You can find it here: https://github.com/trondeau/gr-osmosdr I didn't redo the code to be in the 3.7 API style, just made sure that it could build off gnuradio and run properly. Tom

1 0

Regarding offset tuning in rtl_fm.c - the math
by Aaron Rossetto 25 May '13

25 May '13

Hi all, I recently got a Raspberry Pi and an RTL2832 USB card and have been successful in compiling rtl-sdr and running the associated examples, piping the data up into LabVIEW for analysis with their Demodulation Toolkit. I'm a little weak on the signal processing math knowledge here, so I was wondering if someone could explain the math behind the offset tuning code in rtl_fm's optimal_settings() function. It looks like the function takes the desired center tuning frequency and calculates an integer decimation ratio based on a "capture rate" near 1 MHz and the desired final sampling rate. Then the center frequency is offset by a quarter of the capture rate, and this and the capture rate are used to program the radio. Then in the receive callback, the I/Q data is shifted 90 degrees in rotate_90(). At this point, the I/Q data represents (I presume!) the spectrum around the original desired center frequency and at the original sample rate. How do I get, mathematically speaking, from the oversampled I/Q data centered at the offset frequency to *my* desired center frequency and sample rate? I'm especially curious as to the effect of the frequency offset using that particular value (capture rate/4) and what role the rotation plays in the transformation. Thanks, Aaron

1 0

rtl_fm scanning mods
by Alan Corey 24 May '13

24 May '13

This diff below is actually 2 changes. When scanning it will print the frequency to stderr every time something breaks squelch. When searching/scanning a range it logs active frequencies into a file in /tmp. Two notes: there's an extra \n at the start of each frequency announcement, that's to get around sox's output. If you use something like aucat that doesn't write to the console you don't need that. The file path should be ifdefed and an appropriate Windows path added. This diff was taken before my fix to the scanning step, which may change the context slightly. Alan *** rtl_fm_original.c Wed May 22 13:18:00 2013 --- rtl_fm.c Wed May 22 13:32:53 2013 *************** *** 76,82 **** --- 76,86 ---- static int *atan_lut = NULL; static int atan_lut_size = 131072; /* 512 KB */ static int atan_lut_coef = 8; + static int f_ann = 0; /* freq announced */ + static int searching = 0; + static FILE *flog; /* frequency log */ + struct fm_state { int now_r, now_j; *************** *** 587,592 **** --- 591,603 ---- return; } sr = post_squelch(fm); + if ((sr > 0) && (f_ann == 0) && (fm->freq_len > 1)) { + fprintf(stderr, "\n%f\n",(double)fm->freqs[fm->freq_now]/1000000.0); + f_ann = 1; /* reset next hop */ + if (searching > 0) { + fprintf(flog,"%f\n",(double)fm->freqs[fm->freq_now]/1000000.0); + fflush(flog); + } if (!sr && fm->squelch_hits > fm->conseq_squelch) { if (fm->terminate_on_squelch) { fm->exit_flag = 1;} *************** *** 609,614 **** --- 620,626 ---- /* ignore under runs for now */ fwrite(fm->signal2, 2, fm->signal2_len, fm->file); if (hop) { + f_ann = 0; freq_next = (fm->freq_now + 1) % fm->freq_len; optimal_settings(fm, freq_next, 1); fm->squelch_hits = fm->conseq_squelch + 1; /* hair trigger */ *************** *** 676,681 **** --- 688,696 ---- stop[-1] = '\0'; step = strchr(stop, ':') + 1; step[-1] = '\0'; + flog = fopen("/tmp/freqlog.txt","a"); + if (flog != NULL) + searching = 1; for(i=(int)atofs(start); i<=(int)atofs(stop); i+=(int)atofs(step)) { fm->freqs[fm->freq_len] = (uint32_t)i; ----- Radio Astronomy - the ultimate DX

1 0

Weird rtl_fm bug
by Alan Corey 24 May '13

24 May '13

This only affects scanning, or specifically searching a range of frequencies. I could hear it in the example from usage -f 118M:137M:25k. For some reason the step changes as the loop executes so the frequencies look like: 118950000 118975000 119000000 ok to here 119257000 119282000 119307000 119332000 119357000 119382000 119407000 119432000 119457000 119482000 119507000 119532000 119789000 119814000 119839000 119864000 The frequencies should be at 25 KHz intervals. I don't have a diff because I have several other changes in my version, but my frequency_range() now looks like: void frequency_range(struct fm_state *fm, char *arg) { char *start, *stop, *step; int i; int frst, frstp, frdelta; start = arg; stop = strchr(start, ':') + 1; stop[-1] = '\0'; step = strchr(stop, ':') + 1; step[-1] = '\0'; frst = (int)atofs(start); frstp = (int)atofs(stop); frdelta = (int)atofs(step); fprintf(stderr,"start: %i, stop: %i, step: %i\n",frst,frstp,frdelta); // step was changing here somehow: // for(i=(int)atofs(start); i<=(int)atofs(stop); i+=(int)atofs(step)) for (i=frst; i<=frstp; i+=frdelta) { fm->freqs[fm->freq_len] = (uint32_t)i; fm->freq_len++; } stop[-1] = ':'; step[-1] = ':'; } I added the fr* variables and used them in the loop. It sounds better now that none of the frequencies are off. I'm also logging and those frequencies look OK. Alan ----- Radio Astronomy - the ultimate DX

1 0

RTL SDR LNAs
by Jonathan Rawlinson 24 May '13

24 May '13

Hello All This is the first time I have posted on this list, sorry if I have done it wrong I would like to use a line powered "cheap and nasty" LNA with an RTL dongle. E.g. http://www.amazon.co.uk/Satellite-Signal-Amplifier-Booster-electrosmart%C2%… This may seem a like stupid question (I will ask it anyway) but will the dongle need protecting from the 18V going down the antenna line. I have seen some diagrams with protection and some without. If protection is required, has anyone got any suggestions on how I should do it??? Many thanks Jonathan, M0ZJO

1 0

osmosdr block
by laurent 22 May '13

22 May '13

Hi all, I need some help to resolve my problem with GNURADIO. I Built and installed rtl-sdr and it works well with the dongle terratec. Built and install also the osmosdr package, but when I open grc the block sources rtl does'nt appear. Any ideas? GNUradio for debian package v.3.5.3.2-1 installed. Best regards Laurent

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