[Discuss-gnuradio] TVRX LNA
Hi, Does the TVRX board have a front-end gain stage before the signal is downconverted to IF? I will be using the TVRX and the USRP to capture over the air HDTV signals in a mobile field test. I looked at the schematic for the TVRX board and it looks there isn't a discrete LNA on the board. Does the MT4937 chip have an integrated LNA before the down conversion to IF? I've looked at the tuner datasheet but couldn't tell for sure if there was an LNA. Thanks for any help and information. Nirali ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] TVRX
Matt, Is the TVRX daughter board expected to change anytime in near future? Thanks, Nirali Patel ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] I and Q samples out of FPGA receive chain
Jonathan, Thanks for your response. I can see the ch0rx signal toggling on my Basic RX in slot A using the following command u = usrp.source_c(0,decim_rate=8,fpga_filename="mytestfile.rbf") u._write_oe(0,0x,ox)# for enabling A side Basic RX u._write_fpga_reg(FR_DEBUG_EN, bmFR_DEBUG_EN_RX_A) How do I modify the _write_oe command in order to output enable a Basic TX also on side A? If I use u._write_fpga_reg(FR_DEBUG_EN, bmFR_DEBUG_EN_RX_A | bmFR_DEBUG_EN_TX_A) it does not enable the Basic TX on side A. Thanks again for the help! Nirali > -Original Message- > From: Johnathan Corgan [mailto:[EMAIL PROTECTED] > Sent: Monday, November 05, 2007 10:46 AM > To: Nirali Patel > Cc: discuss-gnuradio@gnu.org > Subject: Re: [Discuss-gnuradio] I and Q samples out of FPGA receive chain > > On 11/2/07, Nirali Patel <[EMAIL PROTECTED]> wrote: > > > In the usrp_std.v file what signals do you recommend to look at the 16 > bits > > I and Q out of the HB filter of the receive_chain? > > Thanks again for you time and help. > > Nirali > > Use the ch0rx and ch1rx signals that go into the rx_buffer. > > -- > Johnathan Corgan > Corgan Enteprises LLC > http://corganenterprises.com/ ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] I and Q samples out of FPGA receive chain
I believe I am enabling the appropriate oe registers using the following commands u = usrp.source_c(0,decim_rate=8,fpga_filename="mytestfile.rbf") subdev = usrp.selected_subdev(u,(1,0)) # for getting signals from slot B TV_RX u._write_oe(0,0x,ox)# for enabling A side Basic RX u._write_fpga_reg(FR_DEBUG_EN, bmFR_DEBUG_EN_RX_A) However, I am perplexed as to why bb_rx_i0 or bb_rx_q0 do not seem to toggle. When I connect ddc0_in_i signals I can see them toggling. I must be doing something really stupid because the rbf file I generated works well with a standard example like usrp_fft.py. So the data path from the ADC to the USB is working well. But somehow I am not able to tap into the I and Q signals out of the receive_chain and see them toggling. In the usrp_std.v file what signals do you recommend to look at the 16 bits I and Q out of the HB filter of the receive_chain? Thanks again for you time and help. Nirali > -Original Message- > From: Johnathan Corgan [mailto:[EMAIL PROTECTED] > Sent: Friday, November 02, 2007 11:56 AM > To: Nirali Patel > Cc: discuss-gnuradio@gnu.org > Subject: Re: [Discuss-gnuradio] I and Q samples out of FPGA receive chain > > Nirali Patel wrote: > > > However I do not see any outputs when I connect these signals to the > > debug pins using debug_0(bb_rx_q0),.debug_1(bb_rx_i0). > > When routing signals through the master_controller debug ports, you'll > need to (on the host at runtime) enable the debug output register, and > set the IO pins as outputs. > > HOWEVER--don't EVER do this unless you are using a BasicRX/TX or LFRX/TX > board in the slots. You can damage the daughterboard, USRP FPGA, or > both otherwise. > > -- > Johnathan Corgan > Corgan Enterprises LLC > http://corganenterprises.com ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] I and Q samples out of FPGA receive chain
Hi, I am using the USRP and TV_RX in slot B to capture over the air signals. I understand the receive chain processing inside of the FPGA and was trying to get the complex 16-bit I and Q samples out at the debug IO pins. As a dry run I tried connecting 12-bit the rx_a_b input to the debug IO pins and could do so successfully by enabling appropriate registers and modifying usrp_std.v. However, in the usrp_std.v I am unable to pinpoint the signals that carry I and Q channels that come out of the receive chain. I tried routing the bb_rx_i0 and bb_rx_q0 signals that come out of the rx_chain_0 block. Since I am running 1rx and 1tx configuration only rx_chain_0 is enabled, I guess. However I do not see any outputs when I connect these signals to the debug pins using debug_0(bb_rx_q0),.debug_1(bb_rx_i0). I have a Basic RX and Basic TX in A slots to look at the outputs. I also tried routing the signals labeled ch0rx, ch1rx to debug pins but still no outputs. Then in my desperation I tried routing the rest of ch2rx to ch7rx to debug pins with a new rbf file everytime but still no outputs. I could verify that the ddc0_in_i signals are toggling but the bb_rx_i0 and bb_rx_q0 do not seem to toggle. I would like to look at individual I Q signals and then eventually connect the interleaved I and Q that go to the USB. Any help/guidelines appreciated. Thanks, Nirali Patel assign ch0rx = counter ? debug_counter : loopback ? loopback_i_0 : bb_rx_i0; assign ch1rx = counter ? debug_counter + 16'd1 : loopback ? loopback_q_0 : bb_rx_q0; assign ch2rx = bb_rx_i1; assign ch3rx = bb_rx_q1; assign ch4rx = bb_rx_i2; assign ch5rx = bb_rx_q2; assign ch6rx = bb_rx_i3; assign ch7rx = bb_rx_q3; wire [15:0] ddc0_in_i,ddc0_in_q,ddc1_in_i,ddc1_in_q,ddc2_in_i,ddc2_in_q,ddc3_in_i,ddc3_i n_q; wire [31:0] rssi_0,rssi_1,rssi_2,rssi_3; adc_interface adc_interface(.clock(clk64),.reset(rx_dsp_reset),.enable(1'b1), .serial_addr(serial_addr),.serial_data(serial_data),.serial_strobe(serial_st robe), .rx_a_a(rx_a_a),.rx_b_a(rx_b_a),.rx_a_b(rx_a_b),.rx_b_b(rx_b_b), .rssi_0(rssi_0),.rssi_1(rssi_1),.rssi_2(rssi_2),.rssi_3(rssi_3), .ddc0_in_i(ddc0_in_i),.ddc0_in_q(ddc0_in_q), .ddc1_in_i(ddc1_in_i),.ddc1_in_q(ddc1_in_q), .ddc2_in_i(ddc2_in_i),.ddc2_in_q(ddc2_in_q), .ddc3_in_i(ddc3_in_i),.ddc3_in_q(ddc3_in_q),.rx_numchan(rx_numchan) ); `ifdef RX_EN_0 rx_chain #(`FR_RX_FREQ_0,`FR_RX_PHASE_0) rx_chain_0 ( .clock(clk64),.reset(1'b0),.enable(enable_rx), .decim_rate(decim_rate),.sample_strobe(rx_sample_strobe),.decimator_strobe(s trobe_decim),.hb_strobe(hb_strobe), .serial_addr(serial_addr),.serial_data(serial_data),.serial_strobe(serial_st robe), .i_in(ddc0_in_i),.q_in(ddc0_in_q),.i_out(bb_rx_i0),.q_out(bb_rx_q0),.debugda ta(debugdata),.debugctrl(debugctrl)); `else assign bb_rx_i0=16'd0; assign bb_rx_q0=16'd0; `endif ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] CIC passband compensation
Hi Firas, Thanks for your response. In an earlier thread you had posted a matlab script called usrpddc.m that calculates the overall frequency response of the usrp rx chain and plots it. This would be very useful to me however, when I try to run it I find it is missing mfilt.cicdecim() function. If you still have this and could make it available it will be a great help. Thanks Nirali Hi Patel, No [CIC non flat response] compensation filter is available. Firas Nirali Patel wrote: > > Hi, > > I am trying to understand the USRP receive chain response and referred to > earlier posts that gave me almost all the information that I needed. > However, I am unsure whether the HB filter compensates for the passband > droop that occurs in the CIC. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] CIC passband compensation
Hi, I am trying to understand the USRP receive chain response and referred to earlier posts that gave me almost all the information that I needed. However, I am unsure whether the HB filter compensates for the passband droop that occurs in the CIC. My understanding of the CIC was that the frequency response has a sinc like function and is typically followed by a FIR which compensates for the sinx/x shape in the passband. Does the HB filter response compensate for the non-flat passband of the CIC? Thanks, Nirali ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Decimate by 2 possible?
Brian, Thanks for your response. > What is your target symbol rate? My target symbol rate is 10.76 MHZ (8-vsb ATSC symbol rate). I need only 2x of this symbol rate, i.e 21.52 Mhz to do down stream processing. >Is there a reason you want to play directly with 32Msps? Only for troubleshooting interpolation-algorithm problems on the downstream board. If I send a lower rate e.g 8Msps then there is a need for interpolation first and it appears that there is a bug in the algorithm for cubic interpolation method on the downstream board that causes sampling offsets. So it would be nice if there was only downsampling involved in getting to 21.52 Mhz. > Maybe it would be better if you decimated to 1x or 2x the symbol rate > and then processed that data on your other board? Yes, you are right. Ultimately I should only send the decimated data. If I use both the CIC and HBF then the lowest combined decimation rate is 8, which gives me 8 Msps output. I might avoid the HBF for now and get a decimation of 4 in the CIC. I found from an earlier post that the file 4rx_0tx.rbf has only CIC and no HBF. Do you know how this file can be generated? I need to start at the toplevel in order to make connections to the debug IO pins. > What do you think? Is this more plausible of a scenario for you? This definitely makes good sense. Thanks for the suggestions! Nirali Patel ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Decimate by 2 possible?
Hi, I am using the TV_RX and USRP to capture the 64 Msps data from the A/D converter and send that to another downstream board for processing. I am connecting the signal from the ADC to the debug IO pins of the FPGA to get to the 16 io_rx[] pins of Basic RX. However, my board-to-board interconnection turned out to have a bandwidth limitation of 50 MHz so I can no longer hope to send 64 Msps raw data from the ADC over the interconnect bus. The next best thing would be to decimate by a factor of 2 and then route the 32 Msps data to the debug pins. I understand the the CIC has a decimation range of [4,5,6,.128] and the HBF decimates by a factor of 2. Is there a way to get an overall decimation of just 2 by possibly bypassing the CIC and using only the HBF? If this sounds like a dumb question then, what would be the best way to get 32 Msps over to the Basic RX card using what's already in the FPGA? Thanks in advance for any suggestions. Nirali ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] 64Mhz Crystal Oscillator part number
Hi, I have a USRP Rev 4.5 and I was trying to find stability information on the 64 Mhz crystal oscillator. However, I am unable to cross-reference it to a manufacturer's part number. The part number on the BOM says X2 is a digikey CTX286LVCT-ND. However the part populated on the USRP is from Ecliptek and the number stamped on the part itself just tells about the frequency and the year/week of production. I am also unsure if this is a TCXO or not. Any help and information appreciated. Thanks, Nirali ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Unable to find field sync for over the air HDTV signal
Hello Eric, > [In looking at interp.py, it could be modified to run something like > 4x faster by using gr.interp_fir_filter_ccf instead of what's in > there. Also, decimating by 10 seems a bit agressive. By 8 would give > you more usable signal, though would require changes in the interp.py > code.] I have gotten a set of RAID 0 drives installed and now I can write with a decimation factor of 8 without any overruns. I would like to modify interp.py to appropriately interpolate and lowpass filter the 8 Msps signal from the USRP. Would it be sufficient if I interpolate by 2? Or do I need a higher, maybe fractional interpolation rate? I am also unsure of what the filter cut-off frequency would need to be after the proper interpolation. If you have any suggestions it would be a great help! Thanks, Nirali ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] TVRX Kit - A Few Queries
>>I ordered Tvrx module and expect it to arrive at my place soon. Hope it will have a manual or imp guidelines on usage. The TVRX will not come with a manual or guidelines on usage. You can find the schematics at http://gnuradio.org/trac/browser/usrp-hw/trunk/tvrx The TVRX module has a Microtune 4937 Tuner Module and here is a link to the datasheet for that http://www.comsec.com/usrp/microtune/4937-DI5-3x8899-2.pdf >>1) What is range of the IF I can set its output to? It has a fixed IF at 44Mhz I believe. A different version of the same tuner module comes with 5.75Mhz IF. Matt, please correct me if I am wrong. >>2) Can I use it for HDTV reception? Yes you can use it for HDTV reception. I am trying to do the same thing and am halfway there. I suggest you start with FM reception or something pretty basic using examples in gnuradio-examples directory. >>3) What is the max voltage swing in the output? Is there a DC offset in it? Ref datasheet mentioned above. Nirali Patel ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Unable to find field sync for over the air HDTV signal
Hello everyone, I am trying to capture a few seconds of over the air HDTV on a file and then decode using the files in gr-atsc module according to the instructions in the README at gr-atsc/src/python. I am using the following command to capture the signals off the air: /usrp_rx_cfile.py -R B -d 10 -f 587M -g 75 test_file, where 587MHz is the center of the 584-590 MHZ UHF band. I can successfully capture about 20 seconds of data without any overruns. After I set up the pipes and start the equalizer, it is unable to find field syncs. At some gain settings it initially detects field sync but loses it later on. Am I lacking enough gain/sensitivity in the front-end of the TV_RX? If so would an lna at the antenna help? Or could I be doing something else that prevents the equalizer to find field sync? I believe a number of folks must have decoded over the air hdtv signals using the TV_RX and USRP. Any suggestions and help appreciated. Thanks, Nirali ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Default FPGA I/O standard
Thanks everyone for the help and information. I also discovered that if you want to increase the drive strength for any IO standard for the FPGA IO pins it is possible through the Assignment Editor in Quartus II under Logic Options by setting current_strength_new to Thanks again for all the information. Nirali -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bahn William L Civ USAFA/DFCS Sent: Tuesday, October 02, 2007 5:15 PM To: discuss-gnuradio@gnu.org Subject: RE: [Discuss-gnuradio] Default FPGA I/O standard > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf > Of Brian Padalino > Sent: Monday, October 01, 2007 5:53 PM > To: Matt Ettus > Cc: discuss-gnuradio@gnu.org > Subject: Re: [Discuss-gnuradio] Default FPGA I/O standard > > On 10/1/07, Matt Ettus <[EMAIL PROTECTED]> wrote: > > I think 3.3V LVTTL and LVCMOS are really the same. > > > > Matt > > According to this: > > http://www.interfacebus.com/voltage_LV_threshold.html > > They are, indeed, basically the same. > > Brian They're the same only different. For most purposes, the differences don't matter too much. The biggest difference is in the output drive capability. LVTTL outputs are required to be able to source/sink 2mA while remaining compliant while LVCMOS outputs are only required to source/sink 100uA. For those interested in the "official" word, refer to the actual JEDEC standard: http://www.jedec.org/download/search/jesd8c.pdf ___ 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
RE: [Discuss-gnuradio] Default FPGA I/O standard
Hi Matt, I modified the usrp_std.v file to make connections to the debug IO pins and then on my PC tried to compile the project using Quartus II software. The compile went successfully, but later when I opened the Pin-Out file under Compilation Report all the signals showed at 3.3V-LVTTL. I had only clicked on the play button after opening the .qpf project. I would like to know if the default settings are still all 3.3V LVCMOS and I inadvertently changed something. If not, I would like to set the 16-bit debug pins to LVCMOS since I am trying to attach a CMOS cable to the pins on basic RX. Could you recommend a way to do this? Do I have to look at IO banking rules etc.? I have some FPGA background but not a whole lot. Thanks, Nirali Patel -Original Message- From: Matt Ettus [mailto:[EMAIL PROTECTED] Sent: Wednesday, September 26, 2007 5:01 PM To: Nirali Patel Cc: discuss-gnuradio@gnu.org Subject: Re: [Discuss-gnuradio] Default FPGA I/O standard Nirali Patel wrote: > Hi all, > > I am trying to find out the default I/O standard e.g LVTTL, LVCMOS that is set on the FPGA general purpose debug pins (16-bits available on the daughter card connectors). I don't have Quartus II installed yet. Is there a way to find out or set this through Python? > 3.3V LVCMOS ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] No horizontal sync with ntsc tv reception
Hi, I am working on ntsc tv reception as a precursor to hdtv reception. I am using usrp_rx_cfile.py to capture samples to a file from the TV_RX board and then playing back using usrp_tv_rcv_nogui.py. The picture displayed does not seem to have horizontal sync (picture keeps moving from left to right). I have tried setting different decimation factors, the best I can use without overruns is a factor of 8 and the picture still rolls in horizontal direction. My understanding was that the decimation factor would only affect the horizontal resolution not the ability to sync, but I could be wrong. The commands that I use for capture and playback are: ./usrp_rx_cfile.py -R B -d 16 -f 531.25M -s tv1.out ./usrp_tv_rcv_nogui.py -f 531.23M -n -i tv1.out sdl where 531.25 Mhz is the picture carrier of the ntsc channel with lower band edge at 530Mhz. I have also tried using -f 533M to set the tuning frequency to centre of the band but no significant change in picture sync. If anyone has experienced similar problem I would appreciate the guidance. Does the antenna setting have any influence on h-sync? My office is in the interior of the building so would it help to move towards the exterior? Thanks in advance for any help. Nirali Patel ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Cautions with _write_oe
Hi, I have the TV_RX board in slot B and Basic RX in slot A of the USRP. I am trying to get the raw A/D data that comes into the FPGA, out on the daughter card connector. I would like to use the 16-bit general purpose debug pins from the FPGA on the connector on Basic RX. However, I'd like to be careful before I write to the direction register using the _write_oe given that an improper setting can cause damage. My question is whether I can have both TV_RX and Basic RX boards plugged in, while I use the _write_oe? If yes, what is the precaution that I have to follow? Any suggestions appreciated. Thanks, Nirali Patel ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Default FPGA I/O standard
Hi all, I am trying to find out the default I/O standard e.g LVTTL, LVCMOS that is set on the FPGA general purpose debug pins (16-bits available on the daughter card connectors). I don't have Quartus II installed yet. Is there a way to find out or set this through Python? Thanks, Nirali Patel DSP Application Engineer Coherent Logix ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] TV_RX anti-aliasing filter
Hello everyone, I am a new user and recently set up the USRP and TV_RX boards to receive FM radio and now trying to take the dive into capturing HDTV. I had a basic, maybe dumb question on the presence of a low pass filter before the A/D converter. Does anyone know if the TV_RX board has an anti-aliasing low pass filter on it? Or within the Microtune 4937 tuner module? I looked at the schematic for the daughter board and the data sheet for 4937 but I am not sure if there is one. The TV_RX I got has an IF frequency of 44MHz and I understand that undersampling it at 64 Msps with the A/D converter causes it to fold to 20 MHz. I wanted to know whether there is or there needs to be a low pass filter before the A/D converter to suppress any energy in the lower frequencies before sampling. Thanks, Nirali Patel DSP Application Engineer Coherent Logix, Inc ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
