Re: [Discuss-gnuradio] Help polarity inversion
Selon Eric Blossom : > On Wed, Mar 18, 2009 at 10:04:27AM -0400, Marco Bottino wrote: > > Hello, > > > > I was doing some test with a 6Volts battery with the USRP in order to be > > able to use my USRP outdoors. > > (Sonnenschein A506/4.2 s http://www.sonnenschein.org/A500.htm) > > Everything was fine when I unintentionally inverted the polarity of the > > battery. > > At the moment, connecting the power converter to the usrp, the led > > doesn't blink anymore and the fan doesn't work too. > > I'm really not familiar with the electronic so I don't know what can be > > happened inverting the plus with the minus... > > Is there any hope to bring back to life my USRP? Can the fuse have saved > > the board? > > Any help will be very happreciated. > > > > Thank you, > > Marco > > The fuse might have saved it. Try replacing it. It's a 3 amp fuse, size > 0603. > > Eric > Ok, it should be fine... Thank you, Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Help polarity inversion
Hello, I was doing some test with a 6Volts battery with the USRP in order to be able to use my USRP outdoors. (Sonnenschein A506/4.2 s http://www.sonnenschein.org/A500.htm) Everything was fine when I unintentionally inverted the polarity of the battery. At the moment, connecting the power converter to the usrp, the led doesn't blink anymore and the fan doesn't work too. I'm really not familiar with the electronic so I don't know what can be happened inverting the plus with the minus... Is there any hope to bring back to life my USRP? Can the fuse have saved the board? Any help will be very happreciated. Thank you, Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: RFID Capture
Hello All, I'm trying to do more or less the same thing as Kevin but with two other readers (a RFIdeas Playback and an OpenPCD) and other kind of cards (HID IClass 2K and Mifare Classic 1K: both working at 13.56MHz). I got an interesting signal just putting my loop antenna attached both to the card and the reader: even if it is a bit weak, I can recognize the tag reply. (USRP 1, BaseRX with the usrp_rx_cfile.py -f 13560833 -r B -d 16) One of the problems I have is that I have to stay as much close as I can to the card to be able to read its response (from more than 3 inches I get an unreadable signal...), so I would like to ask Michael which kind of antenna (and any external things) you used to be able to read the signal from few feet away. Any suggestions will be very well appreciated. Thank you very much, Marco Michael Buettner wrote: > Are you using the ThingMagic in monostatic mode (one antenna that does RX and > TX)? If so, you probably won't be able to see the tag reply. Further down > the receive path the ThingMagic has circuitry that removes the strong TX > signal leaving only the tag reply, but I assume you are tapped in before > that. You MIGHT have better luck if you use the reader in bistatic mode and > tap in at the receive antenna, particularly if you don't use the full 1W > output power. Another option would be to just put the USRP antenna near the > tag, and receive both reader and tag commands there. I have had pretty good > luck with that, and can decode tag responses from a few feet away. > > > michael > > > Hello All, > > I am trying to capture the communications between a RFID reader and > > an EPC Gen 2 tag (920 MHz). I tapped directly into the antenna of a > > Thinkmagic M5e RFID reader. I turn it on and it starts reading the > > > tags. When I look at the raw signal from the usrp or an Agilent > > signal analyzer, I can clearly make out the reader-to-tag data bursts. > > But, I don't see the tag-to-reader bursts. I know they should be > > > considerably smaller in amplitude, but all I see is noise. > > > Has anyone had any luck capturing this type of data? Any suggestions > > would be greatly appreciated. > > > Thanks in advance, > > Kevin > > > > > -- > - > > > ___ > 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] Complex signal to square wave
Hello all! I wrote a script in python that takes a binary file (output of the usrp_rx_cfile.py), convert it in a sequence of complex values and applies a variable threshold in order to convert that complex sequence in a square wave. The complex sequence already represent a square wave, but with a noise and distortions that I want to clean. Now I would like to merge what I've done with the gnuradio language, and this is what I tried: class my_top_block(gr.top_block): def __init__(self): gr.top_block.__init__(self) def block_cplx_to_sq (matrice): output1 = [] d = ds = 0; de = len(matrice); while (d < de): [sequence of 'if..else' to find the correct value of [min,max]] threshold = mean(matrice[min,max]); stad = std(matrice[min_std,max_std]); if stad <= 50: threshold = threshold - 100; soglia_f.append(threshold); if abs(matrice[d]) >= threshold: output1.append(1); else: output1.append(0); d = d + 1; return output1; src = gr.file_source(gr.complex, "Acq_petit", TRUE) BLCK = block_cplx_to_sq (); self.connect(src, BLCK) The problem is that the program still requires something as input of block_cplx_to_sq (and it should be the output of the file_source...). Does anyone have any idea to help me? (maybe some gnuradio function that I don't know that does something like this) Thank you in advance, Kind regards, Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Format and dimension of USRP output samples
Hello everybody, I'm sorry to post once again a question about the dimension and the format of the samples output by the USRP, but it is actually hard for me to understand. I'm using the USRP Motherboard with a LFRX daughterboard. Question: if the ADC has 12 bits, each sample that arrives from the doughterboard is 12 bits real or imaginary. But over the USB the samples (real or imaginary) are 16 bit signed integer. If my resolution is 12 bits, why do I need 16 bits? Moreover, using a program like Baudline, the format of the samples I have to use is complex 32 bits floating point. If they are integer, why floating? Thank you very much, kind regards, Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Re: Complex samples format with ASK
Hello, Selon Paul Mathews <[EMAIL PROTECTED]>: > You have to choose reasonable values for the decimations and filter > parameters. The attached file runs without generating compiler errors, but > it's up to you to take it from here. > Paul > If, as you say, it runs, what does "RuntimeError: complex_to_mag(4): insufficient connected output ports (1 needed, 0 connected)" means? Maybe that the output is not used (even if I don't understand why), so for that it stops? thank you Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Re: Complex samples format with ASK
Hello, thank you very much for answering me. Selon Paul Mathews <[EMAIL PROTECTED]>: > > I know very little about RFID, but I can make these observations on > > > how I would probably perform a naive demodulation of this signal. > > > 1. Tune the USRP to your carrier frequency and bring your signal > > down to baseband (centered around DC). > > 2. Choose an appropriate number of samples per symbol or bit (I'd > > > arbitrarily choose 6 .. or 8). > > 3. Filter the incoming signal to some appropriate spectral mask. > > 4. Find the magnitude (or even power since it saves a sqrt) of the > > complex vector. > > 5. Develop some algorithm which accounts for frequency offset/tracking. > > > 6. Perform hard decisions from the soft decisions you make from the > > algorithm developed in step (5). > > > Marco, > Are you trying to decode the reader transmission, or the tag reply? You may > be able to use a matched filter as a first step to clean up the signal > before > demodulating. I'm not really sure what 13.56 MHz RFID signals look like, but > that > > helps a lot at 915 MHz. > > Regardless, I think step 3 is the key to get you started. You don't want to > just > throw out the I or Q channel. You probably want to use the complex_to_mag > block, > and then the signal will look like what you expect. > > michael > > To try to answer Marco's original question about I/Q directly: the phase > info available from I/Q samples is not directly useful for RFID ASK signals. > However, the calculated magnitude provides slightly better SNR than would > samples of magnitude alone. > > I've done a lot of work with 13 MHz RFID. Most common form of modulation is > Amplitude Shift Keying, a form of AM, with the data stream Manchester > encoded. > http://en.wikipedia.org/wiki/Manchester_coding > A good example of channel filtering and AM demodulation using complex_to_mag > is usrp_am_mw_rcv.py. That example is setup for AM broadcast, so you'll want > to widen the channel filter BW out to accomodate the baud rate you're using, > and, you can eliminate the audio filtering and sink code. I am trying to understand how to modify usrp_am_mw_rcv.py code: I have eliminated everything inherent the volume and the audio and I have modified the parameters in that way: 16 as usrp_decim 1 as chanfilt_decim chan_filt_coeffs: 400e3 as passband cutoff 410e3 as stopband cutoff 1.0 as passband ripple 60 as stopband attenuation Is it correct? (To be more clear I have attached the .py modified file) I think I'll still have some troubles with the GUI, but so far this is the message error I got: [EMAIL PROTECTED]:~/Desktop# ./usrp_am_mw_rcv_002.py -R B -f 1356 Using RX d'board B: LF Rx >>> gr_fir_ccf: using SSE ** (python:6937): WARNING **: IPP request failed with status 1030 FYI: No Powermate or Contour Knob found Traceback (most recent call last): File "./usrp_am_mw_rcv_002.py", line 335, in app = stdgui2.stdapp (wfm_rx_block, "USRP Broadcast AM MW RX modified") File "/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py", line 36, in __init__ wx.App.__init__ (self, redirect=False) File "/usr/lib/python2.5/site-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7935, in __init__ self._BootstrapApp() File "/usr/lib/python2.5/site-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7509, in _BootstrapApp return _core_.PyApp__BootstrapApp(*args, **kwargs) File "/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py", line 39, in OnInit frame = stdframe (self.top_block_maker, self.title, self._nstatus) File "/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py", line 60, in __init__ self.panel = stdpanel (self, self, top_block_maker) File "/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py", line 86, in __init__ self.top_block.start () File "/usr/local/lib/python2.5/site-packages/gnuradio/gr/top_block.py", line 45, in start self._tb.start() File "/usr/local/lib/python2.5/site-packages/gnuradio/gr/gnuradio_swig_py_runtime.py", line 1461, in start return _gnuradio_swig_py_runtime.gr_top_block_sptr_start(*args) RuntimeError: complex_to_mag(4): insufficient connected output ports (1 needed, 0 connected) > The demodulated > output is the 'envelope' of the signal, with an offset the depends on the > percentage of modulation achieved. The RFID reader in Marco's case achieves > 100% modulation, so the offset will be 50% of peak level, like this (fixed > font spacing req'd): >___ ___ ___ > | | | | | | > 0 ___| |___| |___| |___ > > RFID tags typically achieve much lower modulation percentages, depending on > coupling with the reader, like this: > > >___ ______ > | |___| |__| | > 0 ___| |___ > > In either case, you can threshold the data at some value less than the > average peak to do a crude conversion from envelope to bits. In turn, you > can examine the bitstream to
Re: [Discuss-gnuradio] Re: Complex samples format with ASK modulation
Hello CJay, thank you for answering me! Selon "C.cc Jay" <[EMAIL PROTECTED]>: > Hello Marco > > I not familiar with RFID ASK10% or ASK100%. > > (1) > I use usrp -> sinkfft. I can see the wave and tune the target frequency > to 13.56MHz What do you mean with tune the target frequency? Isn't the carrier always at 13.56MHz? > > However, I don't understand the question "why USRP outputs I/Q samples?" > I have to reading more knowledge about communication theory. I asked that because in my opinion I should not need any kind of phase information because of the ASK modulation used that is an amplitude modulation. So I don't know if I have simply to throw away the Q samples or not... > > (2) You want to plot in the time domain > When I got RFID signal, I will do demodulation and get the information > carried by the phase. I still trying. I'm sorry for my ignorance but which is the information carried by the phase? With "demodulation" what do you exactly mean? USRP isn't able to sample directly at the RFID's frequency? Finally, reading the ISO standards it seems that is always used the ASK modulation... isn't it? Thank you, Marco > > CJay > > Marco Bottino wrote: > > hello everybody, > > > > I am using the USRP with LFRX daughterboard to catch an RFID signal ASK > > modulated (frequency 13.56MHz, decimation factor 16). > > I really need an help because I don't understand very well the meaning > > of the > > outputs of my USRP: if the information related to the ASK is only the > > amplitude, so why USRP outputs I/Q samples? > > Which is the meaning of the Q samples? Which is the information carried > > by the > > phase (that should not be important in ASK modulation)? > > If I want to plot in the time domain the samples got, which kind of > > operation is > > necessary (given that I would compare my result with the > > usrp_oscope.py)? > > > > Any kind of help will be really well appreciated. > > Thank you, > > > > Marco > > -- > Posted via http://www.ruby-forum.com/. > > > ___ > 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] Complex samples format with ASK modulation
hello everybody, I am using the USRP with LFRX daughterboard to catch an RFID signal ASK modulated (frequency 13.56MHz, decimation factor 16). I really need an help because I don't understand very well the meaning of the outputs of my USRP: if the information related to the ASK is only the amplitude, so why USRP outputs I/Q samples? Which is the meaning of the Q samples? Which is the information carried by the phase (that should not be important in ASK modulation)? If I want to plot in the time domain the samples got, which kind of operation is necessary (given that I would compare my result with the usrp_oscope.py)? Any kind of help will be really well appreciated. Thank you, Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Problems with the usrp_rx_cfile.py, usrp_fft.py and usrp_oscope.py and RFID signals
Hello, I am a student and I am doing my thesis project on the RFID protocols. At the present time, with the USRP, I am trying to catch the signal between a reader and a tag RFID. As reader I am using an OpendPCD (using the firmware for the Mifare Classic protocol) and as card a Mifare Classic Card. Because of I am a very beginner of USRP and all the rest, I am using the programs usrp_fft.py and usrp_oscope.py and the usrp_rx_cfile.py program with another program called Baudline to analyse the spectrum. My problem is that I can easily see in the frequency domain, using usrp_fft, the carrier at 13.561Mhz, but not the subcarrier that should be a 847KHz modulation of the carrier (probably covered by noise) even if I try to use a baseRX daughterboard instead of the LFRX. Moreover, in the time domain (with the usrp_oscope), I cannot recognize anything interesting. As it isn't enough, with the usrp_rx_cfile and the program baudline I cannot recognize neither the carrier: my opinion is that it is caused by a wrongly interpretation of the bit-length of the samples (and for this I should need a confirmation that the output samples are 16 bit-length). That program supports these formats: alaw ulaw s8 u8 le16 be16 le32f be32f. Does anybody know wich is the format I should use? Probably I'm using wrongly the hardware and the software I have... Could somebody suggest me a solution? Any kind of help will be absolutely well appreciated! thank you, Marco ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
