[Discuss-gnuradio] Re: Open-Hardware
schrieb Marcus D. Leech am 2011-01-12 02:40: Well, I *personally* don't care very much about random-disk-noise, errr, I mean Windows, but I'm sure others do :-) There is a lot of people outside the Linux world, especially in the non-academic hobbyist corner. These people seem to me to try to work with least possible changes, that is install no new OS, install no additional tricky exotic drivers, and at most plug in some USB device. That's perfectly ok for me. If these people should be serverd as well you unfortunately _have_ to to think about Windows, as hard and painful as it may seem. I read the UAC1 specs a year ago and thought Great, you can advertise up to 4MSPS on USB Audio!, but it turned out that it was specified for USB 1.1, which just cannot handle the data rates. :-( Then I found the SDR Widget, and they really get everything out of the Windows UAC1 driver. I thought you couldn't do more than 48Ksps with UAC1, no way no how. You can trick Windows to do 192Ksps via UAC1, I think. No sure if its 16 or 24 bit. Perhaps I should read that spec again, but it seems that UAC2 is the way forward, with 384Ksps audiophile DACs using UAC2 already becoming available. I can think of a way how the SDR Widget people do it: Different firmwares for UAC1 and UAC2. With a third for a more generic interface, this could be compatible and fun at the same time. An interesting device is the AD6655, which is an integrated ADC and signal processing chain (complex DDC, and one or more CIC decimators and FIR filters). Now that is not exactly the cheap one, but with its 150MSPS it would be quite a frequency range with low additional effort. What would be the goal for such a device? Which bandwidth are of interest, which dynamic ranges? Which frequency ranges? Extra frontends? IF from other transceivers or transverters? What would you do with it? Oh, I forgot one interesting device: http//:www.websdr.org/ Seems the hardware info is not linked any more, but its a DDS board with Ethernet interface. Very application specific, but all soldered by hand. Regards Patrick -- Engineers motto: cheap, good, fast: choose any two Patrick Strasser patrick dot strasser at student dot tugraz dot at Student of Telemati_cs_, Techn. University Graz, Austria ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
On 01/12/2011 08:17 AM, Patrick Strasser wrote: Now that is not exactly the cheap one, but with its 150MSPS it would be quite a frequency range with low additional effort. What would be the goal for such a device? Which bandwidth are of interest, which dynamic ranges? Which frequency ranges? Extra frontends? IF from other transceivers or transverters? What would you do with it? Oh, I forgot one interesting device: http//:www.websdr.org/ Seems the hardware info is not linked any more, but its a DDS board with Ethernet interface. Very application specific, but all soldered by hand. No, it's not cheap. But because it has built-in DDC+CIC Decimator, you may not need a largish FPGA to do the DDC+Decimation, so you trade-off a more-expensive ADC against not having an FPGA at all. In terms of an RF front-end, I'd previously observed that the Rx range offered by the WBX covers a very wide swath of interesting frequencies for experimenters, namely 50Mhz to 2.2GHz. The core of that capability is an ADF4350 PLL synthesizer, and an ADL5387 quadrature mixer. -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
schrieb Marcus D. Leech am 2011-01-12 02:40: There is a lot of people outside the Linux world, especially in the non-academic hobbyist corner. These people seem to me to try to work with least possible changes, that is install no new OS, install no additional tricky exotic drivers, and at most plug in some USB device. That's perfectly ok for me. If these people should be serverd as well you unfortunately _have_ to to think about Windows, as hard and painful as it may seem. Yup, I reluctantly agree. But I have to assume that UAC2 is the future of USB Audio devices, and as such, should probably be the way to go forward. I'm pretty sure that the USB consortium didn't invent UAC2 purely for LInux users :-) Now, to keep ideas ball rolling here: So, by way of a start on a cheap(ish) receive chain block-diagram, I whipped-up this: http://www.sbrac.org/files/digital_receiver2.pdf This has a reasonable RF Rx chain, and includes a reasonable (20Msps) ADC. The trick is that instead of doing decimation in an FPGA, you select the correct filter from the bank, and change the ADC clock rate. Discrete passive filters are reasonably easy to design and fabricate, and if there are only, let's say, four of them, covering 4 different desired SPS rates, that might be acceptable. Also, the design terminates in an FMC connector, which allows you to mate this up with something like a Xilinx FPGA+1GiGe card, like the SP601 or similar. If one desired USB instead, then a simple EZ-FX2 USB-2.0 card with an FMC connector on it, and whatever logic was necessary to grab samples from the ADC could be designed and built. A wrinkle in such a design is that one is at the mercy of the tuning resolution of the down-converter, since there's potentially no DDC (unless you implemented one on the FPGA card). -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
On 12.01.2011 20:22, Marcus D. Leech wrote: http://www.sbrac.org/files/digital_receiver2.pdf The RF range is interesting, from 70 MHz to 2.2 GHz. For USRP you would need 2 different boards to cover that range, or invest much more money into the WBX transceiver. This has a reasonable RF Rx chain, and includes a reasonable (20Msps) ADC. The trick is that instead of doing decimation in an FPGA, you select the correct If connected to a Xilinx board, FIR and decimation could still be done in the FPGA. Also, the design terminates in an FMC connector, which allows you to mate this up with something like a Xilinx FPGA+1GiGe card, like the SP601 or similar. This would be a very powerful combination and only $250 for the mainboard. With large memory 128 MB DDR2 memory controller, 32 DSP slices, MicroBlaze processing with MMU and FPU inside a Spartan-6. If one desired USB instead, then a simple EZ-FX2 USB-2.0 card with an FMC connector on it, and whatever logic was necessary to grab samples from the ADC could be designed and built. There's a cheap one here, with USB2 and Spartan3, only 70€ ($100) http://www.ztex.de/usb-fpga-1/usb-fpga-1.2.d.html Or this one for 145€? http://www.cesys.com/fpga/spartan/efm01_en.html Do you think the FMC interface can be realized with the 52 Xilinx GPIO pins, just with the specific FMC driver software? A wrinkle in such a design is that one is at the mercy of the tuning resolution of the down-converter, since there's potentially no DDC (unless you implemented one on the FPGA card). Is this really a problem? For spectral analysis this is only an axis shift. For demodulation you would have to do some kind of adaptive doppler compensation and phase tracking anyway. Could all this be done by continuously changing the DDC parameters over the wire? ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
On 12.01.2011 20:22, Marcus D. Leech wrote: If connected to a Xilinx board, FIR and decimation could still be done in the FPGA. Agreed. There's a cheap one here, with USB2 and Spartan3, only 70€ ($100) http://www.ztex.de/usb-fpga-1/usb-fpga-1.2.d.html Or this one for 145€? http://www.cesys.com/fpga/spartan/efm01_en.html Do you think the FMC interface can be realized with the 52 Xilinx GPIO pins, just with the specific FMC driver software? Quite possibly, don't actually know that much about FMC, but my impression is that it's a fairly-generic way of putting expansion goop onto a generic FPGA board. Is this really a problem? For spectral analysis this is only an axis shift. For demodulation you would have to do some kind of adaptive doppler compensation and phase tracking anyway. Could all this be done by continuously changing the DDC parameters over the wire? Maybe, maybe not. Depends on the applications, but I'm guessing that a significant number of applications can get away with the fact that their signal of interest isn't exactly at DC, and do the DDC in software. For example, I happen to be interested in signals centered at 1420.40575Mhz. But I'd be perfectly happy if the 0Hz in the signals was actually at 1420.400MHz--I could compensate in the software side. Resolution of 50KHz or better should be achievable with the PLL I've shown on the block diagram. Phase noise improves with larger resolutions, however. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
If one desired USB instead, then a simple [Cypress] EZ-FX2 USB-2.0 card with an FMC connector on it, and whatever logic was necessary to grab samples from the ADC could be designed and built. By the way, USB3 is now hitting the mainstream, with PCI boards, motherboards, disk drives and USB sticks from all the major vendors. It provides a significant bandwidth boost over USB2 (it's designed for 3Gbits/sec, both ways simultaneously). This would be very useful to any newly designed USRP-like device. I haven't investigated what chips could replace the EZ-FX2 in a USB3 USRP. Oddly, the Cypress site seems to know nothing about USB3 devices! John ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
By the way, USB3 is now hitting the mainstream, with PCI boards, motherboards, disk drives and USB sticks from all the major vendors. It provides a significant bandwidth boost over USB2 (it's designed for 3Gbits/sec, both ways simultaneously). This would be very useful to any newly designed USRP-like device. I agree that it's worth considering, I think it has extended range as well. Competing very firmly with GiGe! I haven't investigated what chips could replace the EZ-FX2 in a USB3 USRP. Oddly, the Cypress site seems to know nothing about USB3 devices! John Yes, I found that same thing. Seems odd that Cypress wouldn't be one of the front-runners for USB-3.0. I will point out that one of the enticing things about 1GiGe is that you can run it over extended distances. Which for me is very interesting, since you could put a receiver at each antenna (think Alan Telescope Array), and haul signals back via 1GiGe. With USB-2.0, you can't do that without a funky device like the ICRON Ranger series (which inside, just re-packages USB-2.0 over 1GiGe, as far as I know). -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Re: Open-Hardware
schrieb Marcus D. Leech on 2011-01-12 01:16: For certain classes of high-bandwidth applications, you're willing to sacrifice number of bits for bandwidth. For sure. But you have to commit that your usecase is more the corner case then the mainstream. With your CPLD mentions below this should not be a big deal. the FX2 has an external FIFO interface, intended to handle storage devices, but interfacing to a high-speed dual-channel-simultaneously-sampled ADC shouldn't be that hard--might require an uber-cheap CPLD to handle some of the handshaking. AFAIK the SSRP is just shoveling bits from the ADC to the FX2. An other way would be to change the interface, which would very likely be Gigabit-Ethernet. I haven't found a cheap way of doing GiGe. GiGe is for high end. It adds comlexity on the network and host side (configuration...) and is IMO unnecessary. Of course you get speedup by 2.5 over USB, but as ham and hobbyist you hardly need all the USB capacity. What I'd like to have is something like the Digilent Basys2/Nexys2. A capable USB interface, some CPLD/FPGA for the hard stuff, maybe a microcontroller, some memmory, buttons, 7-segment-display, and connectors like SD card etc. With examples and modules like for the Digilent parts this would make it easy to start all kinds of projects. The board are already cheap, but not OS. If it was compatible with the PMOD module, this gave a good starting point for working strait and for custom modules like the Charleston SDR. If people agree on a bus, modules could be stacked: AD module, mixer module, filtering module, LNA or transmitter module. Regards Patrick ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Re: Open-Hardware
schrieb Marcus D. Leech on 2011-01-12 01:44: Another thought I had earlier today is that with UAC2 (USB Audio Class version 2), there's no limit on the sample rate that a UAC2 device can advertise, so it might be nice to make a USB-SDR device appear to be a UAC2 compliant device. [Well, OK that's not strictly true, you can advertise up to something like 400Msps]. Perhaps we can overload the control interface a bit (volume control becomes RF gain, use some other thingy in the control portion of UAC2 for setting frequency). You just ad a second interface that is HID, which is available on every platform and easy to handle. That's how all the soundcard-like DDS do it. The only problem is that Microsoft promised in 2005 to implement UAC2, but forgot to do it until now. BTW they have a big mess with USB, as Daniel Mack, Linux UAC2 author wrote: Inevery cruel reincarnation of their OS, it has different issues. I spare you the terrible details an leave out the rest of his summary. I read the UAC1 specs a year ago and thought Great, you can advertise up to 4MSPS on USB Audio!, but it turned out that it was specified for USB 1.1, which just cannot handle the data rates. :-( Then I found the SDR Widget, and they really get everything out of the Windows UAC1 driver. Regards Patrick ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
On Jan 11, 2011, at 5:15 PM, Patrick Strasser wrote: The only problem is that Microsoft promised in 2005 to implement UAC2, but forgot to do it until now. BTW they have a big mess with USB, as Daniel Mack, Linux UAC2 author wrote: Inevery cruel reincarnation of their OS, it has different issues. I spare you the terrible details an leave out the rest of his summary. I have to give MS credit for backwards-compatibility, though. As of Windows 7, they still support mis-identifying a GPS receiver as a serial port mouse, thus causing all sorts of delightful hijinks with the mouse pointer. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Re: Open-Hardware
schrieb Marcus D. Leech on 2011-01-12 01:44: You just ad a second interface that is HID, which is available on every platform and easy to handle. That's how all the soundcard-like DDS do it. Ah, yes of course. The only problem is that Microsoft promised in 2005 to implement UAC2, but forgot to do it until now. BTW they have a big mess with USB, as Daniel Mack, Linux UAC2 author wrote: Inevery cruel reincarnation of their OS, it has different issues. I spare you the terrible details an leave out the rest of his summary. Well, I *personally* don't care very much about random-disk-noise, errr, I mean Windows, but I'm sure others do :-) I read the UAC1 specs a year ago and thought Great, you can advertise up to 4MSPS on USB Audio!, but it turned out that it was specified for USB 1.1, which just cannot handle the data rates. :-( Then I found the SDR Widget, and they really get everything out of the Windows UAC1 driver. I thought you couldn't do more than 48Ksps with UAC1, no way no how. Perhaps I should read that spec again, but it seems that UAC2 is the way forward, with 384Ksps audiophile DACs using UAC2 already becoming available. An interesting device is the AD6655, which is an integrated ADC and signal processing chain (complex DDC, and one or more CIC decimators and FIR filters). It can produce 4 discrete output channels, but the cool thing is the built-in DDC+etc chain. Doing the BOM math, going with something like the AD6655 then straight into the FX2 would be cheaper than somewhat-cheaper-highspeed-ADC+FPGA+FX2. The AD6655 is designed as an (non-zero) IF sampler, and I haven't read enough of the datasheet to determine if it can do simultaneous sampled I/Q with a quadrature D-C front-end in front of it. It *does* have two ADCs, but they're intended for diversity reception, rather than quadrature sampling--it has its own quadrature converter inside it. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
