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[replying to OP] Ethernet is definitely a reasonable-risk option. For 20Mbytes/sec you will need Gigabit Ethernet, so an FPGA with a hard MAC is a good idea, e.g. Vitex-5 (other vendors' products may be equally suitable). You will want a s/w element to accept TCP/IP packets (a stack in HDL is theoretically possible). You can send UDP/IP from HDL. PCIe might be a better idea, but never done it... --------------------------------------- Posted through http://www.FPGARelated.comArticle: 153551
Bill Valores <bill.valores@gmail.com> wrote: >Hello all, > >My team needs to design our own piece of testing equipment for our >project. I'll spare you the gory details, and just say that we will >need to collect data at some 20 Mbyte/sec (possibly continuously) and >somehow get it to a PC computer running Windows. A fancy GUI >application will then present this to the operator. A similar link is >necessary in the other direction for signal injection. > >The FPGA does some data processing, so we can't just buy a data >capture card. We may consider a capturing card to interface with the >FPGA digitally. > >So my question is: What's your recommendation for the PC-FPGA >communication? Given a fairly skilled engineering team and a >management that understands this is not a cheap quickie (but still >wants to keep costs and efforts at a minimum, of course) what would >you suggest? USB? PCIe? Ethernet? Capture data from debug pins? >Something else? > >And: Can anyone give me an idea about what we're up against (costs and >time) based upon experience? FTDI has parallel USB interface chips: http://www.ftdichip.com/Products/ICs/FT2232H.htm USB gives the least hassle to a user. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------Article: 153552
Arlet Ottens <usenet+5@c-scape.nl> wrote: >On 03/27/2012 02:22 PM, Bill Valores wrote: >> Thanks for your answers so far. I'll address some issues shortly. >> >> Yes, National Instruments was one of the first thoughts. The main >> concern about this solution the per unit price in case we want to >> duplicate the system. But it's definitely not ruled out. >> >> Buying an PCIe development board is indeed easy. Implementing the >> logic for the PCIe interface (I suppose DMA is the only option) and >> writing the Windows drivers doesn't sound like a trip in the >> rosegarden to me. >> >> As for the form factor: A separate box solution, or a card stuck in >> the PC, both go. Data needs to be flowing in both directions >> simultaneously at 20 MB/sec in each direction. >> >> As for USB: It's a generic name. The only solution we're aware of is >> Cypress' EZUSB. Whether it fits the data rates is considered a >> "maybe". > >I wouldn't recommend USB. It's too flaky for reliable transfer. That depends on the software driver and the EMC/EMI protection applied to the data lines. >Why not ethernet ? Interfacing with a PHY is simple, and if you use UDP >packets in a controlled environment (fixed IP addresses), the MAC layer >is fairly straightforward too. > >Capturing the UDP traffic can be done with simple tool like netcat. Libpcap is easy to use but don't forget that when using ethernet you are usually sharing the bandwidth, have to depend on the quality of network components and the people who maintain it. I wouldn't go that route unless it s absolutely necessary. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------Article: 153553
On 03/27/2012 06:36 PM, Nico Coesel wrote: >> Capturing the UDP traffic can be done with simple tool like netcat. > > Libpcap is easy to use but don't forget that when using ethernet you > are usually sharing the bandwidth, have to depend on the quality of > network components and the people who maintain it. I wouldn't go that > route unless it s absolutely necessary. It sounded like the OP wouldn't object to setting up a dedicated connection for this project. If not, USB would present a similar problem, but even less controllable. With USB, bandwidth depends a lot on efficiency of driver and host implementation, and can vary with the amount of bit stuffing.Article: 153554
On Mar 27, 5:09=A0pm, "RCIngham" <robert.ingham@n_o_s_p_a_m.n_o_s_p_a_m.gmail.com> wrote: > [replying to OP] > > Ethernet is definitely a reasonable-risk option. For 20Mbytes/sec you wil= l > need Gigabit Ethernet, so an FPGA with a hard MAC is a good idea, e.g. > Vitex-5 (other vendors' products may be equally suitable). I think this blog post summarizes the Ethernet option pretty well. Even though it looks like it was written to promote a certain solution, the points made appear to be valid. http://billauer.co.il/blog/2011/11/gigabit-ethernet-fpga-xilinx-data-acquis= ition/ It's indeed true that using UDP eliminates the need to develop a driver for Windows. Not that I'm 100% sure how to make the computer link between the Ethernet address and the FPGA's IP address (implement ARP on the FPGA as well). This way or another, data has to be stored on some very large memory to allow retransmissions. Yet another option not ruled out, but not a clear winner either.Article: 153555
> > FTDI has parallel USB interface chips:http://www.ftdichip.com/Products/ICs/FT2232H.htm > > USB gives the least hassle to a user. That's an interesting one. Will definitely follow that up.Article: 153556
On 03/27/2012 07:26 PM, Bill Valores wrote: > It's indeed true that using UDP eliminates the need to develop a > driver for Windows. Not that I'm 100% sure how to make the computer > link between the Ethernet address and the FPGA's IP address (implement > ARP on the FPGA as well). This way or another, data has to be stored > on some very large memory to allow retransmissions. Yet another option > not ruled out, but not a clear winner either. Depends on how you want to use it. Is it strictly used in a controlled environment ? If so, you could hard code the MAC adress in the FPGA, or send an initial packet from PC to FPGA. The FPGA could then extract the addresses from the PC's packet, and swap them in its responses.Article: 153557
Le 27/03/2012 19:35, Bill Valores a écrit : > >> >> FTDI has parallel USB interface chips:http://www.ftdichip.com/Products/ICs/FT2232H.htm >> >> USB gives the least hassle to a user. > > That's an interesting one. Will definitely follow that up. I am currently using one in a project, works a treat (though I don't transfer 20MB/s) NicolasArticle: 153558
On Tue, 27 Mar 2012 04:10:18 -0700, Bill Valores wrote: > Hello all, > > My team needs to design our own piece of testing equipment for our > project. I'll spare you the gory details, and just say that we will need > to collect data at some 20 Mbyte/sec (possibly continuously) and somehow > get it to a PC computer running Windows. A fancy GUI application will > then present this to the operator. A similar link is necessary in the > other direction for signal injection. > > The FPGA does some data processing, so we can't just buy a data capture > card. We may consider a capturing card to interface with the FPGA > digitally. > > So my question is: What's your recommendation for the PC-FPGA > communication? Given a fairly skilled engineering team and a management > that understands this is not a cheap quickie (but still wants to keep > costs and efforts at a minimum, of course) what would you suggest? USB? > PCIe? Ethernet? Capture data from debug pins? Something else? > > And: Can anyone give me an idea about what we're up against (costs and > time) based upon experience? > > Purchasing equipment and IP cores is fine as long as the costs can be > justified in terms of saved engineering time. It's our own salaries > weighted against spending the money on products (with due risk > calculations and stuff). I was going to just say USB, then I read all the responses. And, I'm still going to just say "USB"! I've seen FPGA designers struggling to get PCI working in an FPGA. They did it, but it wasn't a trivial task and it took a lot of messing around. Implementing a client-side USB in FPGA should be way easier than PCI, and if you can get an FTDI chip to work -- go for it. Another thing that I would look into, without really expecting to actually use it, would be SATA. Yes, a disk-drive interface. I've seen it suggested, and the reasons given sounded compelling -- but I haven't done it, and it is most certainly an oddball approach. My understanding is that the hardware is easy, but you'd have to write Windows drivers. No matter what you do, though, I think your biggest problem isn't going to be getting the bits into the PC hardware: I think it's going to be getting past the Windows software to actually _do_ something with those bits. I wouldn't even think about trying this unless I had some Windows driver whizzes to help me out. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.comArticle: 153559
In comp.arch.fpga, Bill Valores <bill.valores@gmail.com> wrote: > On Mar 27, 5:09 pm, "RCIngham" ><robert.ingham@n_o_s_p_a_m.n_o_s_p_a_m.gmail.com> wrote: >> [replying to OP] >> >> Ethernet is definitely a reasonable-risk option. For 20Mbytes/sec you will >> need Gigabit Ethernet, so an FPGA with a hard MAC is a good idea, e.g. >> Vitex-5 (other vendors' products may be equally suitable). > > I think this blog post summarizes the Ethernet option pretty well. > Even though it looks like it was written to promote a certain > solution, the points made appear to be valid. > > http://billauer.co.il/blog/2011/11/gigabit-ethernet-fpga-xilinx-data-acquisition/ > > It's indeed true that using UDP eliminates the need to develop a > driver for Windows. Not that I'm 100% sure how to make the computer > link between the Ethernet address and the FPGA's IP address (implement > ARP on the FPGA as well). This way or another, data has to be stored > on some very large memory to allow retransmissions. Yet another option > not ruled out, but not a clear winner either. I'm not sure it does work (need to look it up sometime or just test), but if you use ethernet as a point-to-point connection, you may be able to just use the broadcast address and don't even need to use ARP. -- Stef (remove caps, dashes and .invalid from e-mail address to reply by mail) Blessed is the man who, having nothing to say, abstains from giving wordy evidence of the fact. -- George EliotArticle: 153560
Tim Wescott <tim@seemywebsite.com> wrote: >On Tue, 27 Mar 2012 04:10:18 -0700, Bill Valores wrote: > >> Hello all, >> >> My team needs to design our own piece of testing equipment for our >> project. I'll spare you the gory details, and just say that we will need >> to collect data at some 20 Mbyte/sec (possibly continuously) and somehow >> get it to a PC computer running Windows. A fancy GUI application will >> then present this to the operator. A similar link is necessary in the >> other direction for signal injection. >> >> The FPGA does some data processing, so we can't just buy a data capture >> card. We may consider a capturing card to interface with the FPGA >> digitally. >> >> So my question is: What's your recommendation for the PC-FPGA >> communication? Given a fairly skilled engineering team and a management >> that understands this is not a cheap quickie (but still wants to keep >> costs and efforts at a minimum, of course) what would you suggest? USB? >> PCIe? Ethernet? Capture data from debug pins? Something else? >> >> And: Can anyone give me an idea about what we're up against (costs and >> time) based upon experience? >> >> Purchasing equipment and IP cores is fine as long as the costs can be >> justified in terms of saved engineering time. It's our own salaries >> weighted against spending the money on products (with due risk >> calculations and stuff). > >No matter what you do, though, I think your biggest problem isn't going >to be getting the bits into the PC hardware: I think it's going to be >getting past the Windows software to actually _do_ something with those >bits. I wouldn't even think about trying this unless I had some Windows >driver whizzes to help me out. It depends. About a decade ago I was involved in developing a PCI card (I was responsible for the FPGA design). Writing the Windows driver proved to be the biggest challenge. We didn't even got to the point of using memory-to-memory transfers. Nowadays there is a library called libusb which can deal with a lot of the USB complexities from userspace (application level). It should be relatively easy to get a self build USB device going. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------Article: 153561
> Another thing that I would look into, without really expecting to > actually use it, would be SATA. Yes, a disk-drive interface. I've seen > it suggested, and the reasons given sounded compelling -- but I haven't > done it, and it is most certainly an oddball approach. My understanding > is that the hardware is easy, but you'd have to write Windows drivers. I'd say SATA is not so easy as it could sound. Plus the FPGA will have to have transceivers afaik. Anyway, is there any useful information about implementing SATA in FPGA except a simple SATA standard? Regards, Tomas D.Article: 153562
> It's indeed true that using UDP eliminates the need to develop a > driver for Windows. Not that I'm 100% sure how to make the computer > link between the Ethernet address and the FPGA's IP address (implement > ARP on the FPGA as well). This way or another, data has to be stored > on some very large memory to allow retransmissions. Yet another option > not ruled out, but not a clear winner either. Well, I've made UDP communication from FPGA to PC and it runs at almost 100MB/s without any issues. The ARP/setup/etc stuff is processed by softcpu+LwIP, all the other data streaming is made in hardware. I'd say it's really easy to do UDP streaming on FPGA side, but I am not sure about the PC software. Regards, Tomas D.Article: 153563
On 27/03/2012 13:10, Bill Valores wrote: > Hello all, > > My team needs to design our own piece of testing equipment for our > project. I'll spare you the gory details, and just say that we will > need to collect data at some 20 Mbyte/sec (possibly continuously) and > somehow get it to a PC computer running Windows. A fancy GUI > application will then present this to the operator. A similar link is > necessary in the other direction for signal injection. > > The FPGA does some data processing, so we can't just buy a data > capture card. We may consider a capturing card to interface with the > FPGA digitally. > > So my question is: What's your recommendation for the PC-FPGA > communication? Given a fairly skilled engineering team and a > management that understands this is not a cheap quickie (but still > wants to keep costs and efforts at a minimum, of course) what would > you suggest? USB? PCIe? Ethernet? Capture data from debug pins? > Something else? > > And: Can anyone give me an idea about what we're up against (costs and > time) based upon experience? > > Purchasing equipment and IP cores is fine as long as the costs can be > justified in terms of saved engineering time. It's our own salaries > weighted against spending the money on products (with due risk > calculations and stuff). > > Thanks in advance, > Bill Is Windows a requirement? Dealing with things like raw Ethernet packets to keep overhead to an absolute minimum is an easy job in Linux. (If you don't want to think about ARP, IP addresses, etc., why not force the FPGA to have MAC address 1, and the dedicated PC interface to have MAC address 2 - then send packets with nothing but the Ethernet frame overhead.) It also means that the data packets won't have to compete for bandwidth with other things Windows will want to send over the interface, such as broadcasts scanning for network shares, ARP requests, or (if you are not careful) malware sending out spam...Article: 153564
"scrts" <hidden@email.com> wrote in message news:jku8sg$b46$1@dont-email.me... > I'd say SATA is not so easy as it could sound. Plus the FPGA will have to > have transceivers afaik. Anyway, is there any useful information about > implementing SATA in FPGA except a simple SATA standard? Quick google: http://www.xilinx.com/support/documentation/application_notes/xapp870.pdf http://www.altera.com/literature/wp/wp-01093-arria-iv-gx-sata-sas.pdfArticle: 153565
scrts <hidden@email.com> wrote: > > It's indeed true that using UDP eliminates the need to develop a > > driver for Windows. Not that I'm 100% sure how to make the computer > > link between the Ethernet address and the FPGA's IP address (implement > > ARP on the FPGA as well). This way or another, data has to be stored > > on some very large memory to allow retransmissions. Yet another option > > not ruled out, but not a clear winner either. > Well, I've made UDP communication from FPGA to PC and it runs at almost > 100MB/s without any issues. The ARP/setup/etc stuff is processed by > softcpu+LwIP, all the other data streaming is made in hardware. I'd say > it's really easy to do UDP streaming on FPGA side, but I am not sure > about the PC > software. FT(2)232H needs only a fifo and a not to complex state machine. For the host side, look into libftdi http://www.intra2net.com/en/developer/libftdi/examples/stream_test.c for a sample implementation. -- Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------Article: 153566
On 27/03/2012 12:10, Bill Valores wrote: > Hello all, > > My team needs to design our own piece of testing equipment for our > project. I'll spare you the gory details, and just say that we will > need to collect data at some 20 Mbyte/sec (possibly continuously) and > somehow get it to a PC computer running Windows. A fancy GUI > application will then present this to the operator. A similar link is > necessary in the other direction for signal injection. > > The FPGA does some data processing, so we can't just buy a data > capture card. We may consider a capturing card to interface with the > FPGA digitally. > > So my question is: What's your recommendation for the PC-FPGA > communication? Given a fairly skilled engineering team and a > management that understands this is not a cheap quickie (but still > wants to keep costs and efforts at a minimum, of course) what would > you suggest? USB? PCIe? Ethernet? Capture data from debug pins? > Something else? > > And: Can anyone give me an idea about what we're up against (costs and > time) based upon experience? > > Purchasing equipment and IP cores is fine as long as the costs can be > justified in terms of saved engineering time. It's our own salaries > weighted against spending the money on products (with due risk > calculations and stuff). > > Thanks in advance, > Bill I've done this three different ways but not quite at your speed: FTDI chip and USB - least effort but I only went up to perhaps 4 Mbyte/s - I always worry about USB. Ethernet - FPGA -> uP with the FPGA mapped into uP memory - can sustain wirespeed with 100Mbit Ethernet but that isn't fast enough for you. The approach would work with a processor with a Gbit Ethernet interface. We use these in numbers (up to 8) with one PC and going in both directions - total IO about 40 Mbyte/s FPGA -> PCI // IO card in PC. This could sustain 20Mbyte/s to disk on a reasonable PC (Windows XP and (don't laugh) VB6). The IO card we used was Adlink PCI 7300A (or something like). They probably do a better one now. This system all worked quite well and happily fills up Terrabyte hard drives. I just noticed that you need both directions - that gets harder because when data goes from PC to FPGA you either need a big buffer in the FPGA or real time data from the PC. If you use USB and standard drivers you should allow for at least 0.5 seconds of buffer on the FPGA (either direction). The Adlink driver didn't need any FPGA side buffering for data into the PC but we never used it the other way round. PC's are quite good at buffering incoming Ethernet data but you'll need to do the work on the FPGA side for the other direction. We like to have at least 1 second of buffer ! This has all got a bit rambly - hope you get some ideas you can use. Michael KellettArticle: 153567
MK <mk@nospam.co.uk> wrote: > FTDI chip and USB - least effort but I only went up to perhaps 4 Mbyte/s > - I always worry about USB. We use it at > 16 MiByte/s ... -- Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------Article: 153568
On Wed, 28 Mar 2012 08:51:16 +0300, scrts wrote: >> Another thing that I would look into, without really expecting to >> actually use it, would be SATA. Yes, a disk-drive interface. I've >> seen it suggested, and the reasons given sounded compelling -- but I >> haven't done it, and it is most certainly an oddball approach. My >> understanding is that the hardware is easy, but you'd have to write >> Windows drivers. > > I'd say SATA is not so easy as it could sound. Plus the FPGA will have > to have transceivers afaik. Anyway, is there any useful information > about implementing SATA in FPGA except a simple SATA standard? You could be quite right -- if you look at my wording, you'll see that I had that thought in mind. The article that I was going from was pushing it as a good way to get real-time comms in and out of a PC; it may not be worth the hassle if all you want is throughput but don't care as much about latency. Or, it may not be worth the hassle at all. (I think that the best way to use a PC in a real-time system is as a serial terminal, to talk to the processor that's actually doing the work. But then, I lost patience with PCs a long, long time ago). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.comArticle: 153569
On Wed, 28 Mar 2012 17:23:29 +0100, MK wrote: > On 27/03/2012 12:10, Bill Valores wrote: >> Hello all, >> >> My team needs to design our own piece of testing equipment for our >> project. I'll spare you the gory details, and just say that we will >> need to collect data at some 20 Mbyte/sec (possibly continuously) and >> somehow get it to a PC computer running Windows. A fancy GUI >> application will then present this to the operator. A similar link is >> necessary in the other direction for signal injection. >> >> The FPGA does some data processing, so we can't just buy a data capture >> card. We may consider a capturing card to interface with the FPGA >> digitally. >> >> So my question is: What's your recommendation for the PC-FPGA >> communication? Given a fairly skilled engineering team and a management >> that understands this is not a cheap quickie (but still wants to keep >> costs and efforts at a minimum, of course) what would you suggest? USB? >> PCIe? Ethernet? Capture data from debug pins? Something else? >> >> And: Can anyone give me an idea about what we're up against (costs and >> time) based upon experience? >> >> Purchasing equipment and IP cores is fine as long as the costs can be >> justified in terms of saved engineering time. It's our own salaries >> weighted against spending the money on products (with due risk >> calculations and stuff). >> >> Thanks in advance, >> Bill > > I've done this three different ways but not quite at your speed: > > FTDI chip and USB - least effort but I only went up to perhaps 4 Mbyte/s > - I always worry about USB. > > Ethernet - FPGA -> uP with the FPGA mapped into uP memory - can sustain > wirespeed with 100Mbit Ethernet but that isn't fast enough for you. The > approach would work with a processor with a Gbit Ethernet interface. We > use these in numbers (up to 8) with one PC and going in both directions > - total IO about 40 Mbyte/s > > FPGA -> PCI // IO card in PC. This could sustain 20Mbyte/s to disk on a > reasonable PC (Windows XP and (don't laugh) VB6). The IO card we used > was Adlink PCI 7300A (or something like). They probably do a better one > now. This system all worked quite well and happily fills up Terrabyte > hard drives. > > I just noticed that you need both directions - that gets harder because > when data goes from PC to FPGA you either need a big buffer in the FPGA > or real time data from the PC. FPGA -> PCI -> PC should let the PC shove data into buffers in RAM, then have the FPGA extract it via DMA -- but that'll complicate your PCI interface. > If you use USB and standard drivers you should allow for at least 0.5 > seconds of buffer on the FPGA (either direction). Is that still the case if you're using isochronous transfers, and making sure that the PC is tuned for feeding your app? > The Adlink driver didn't need any FPGA side buffering for data into the > PC but we never used it the other way round. > > PC's are quite good at buffering incoming Ethernet data but you'll need > to do the work on the FPGA side for the other direction. We like to have > at least 1 second of buffer ! > > This has all got a bit rambly - hope you get some ideas you can use. > > Michael Kellett -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.comArticle: 153570
> >>> As for USB: It's a generic name. The only solution we're aware of is >>> Cypress' EZUSB. Whether it fits the data rates is considered a >>> "maybe". >> I got 30+ MB/sec both in and out (not simultaneously) with a Cypress EZUSB (CY7C68013A) chip on a Dell desktop with a core2 Duo CPU. It was very impressive. JonArticle: 153571
Am 27.03.2012 13:10, schrieb Bill Valores: > Hello all, > > My team needs to design our own piece of testing equipment for our > project. I'll spare you the gory details, and just say that we will > need to collect data at some 20 Mbyte/sec (possibly continuously) and > somehow get it to a PC computer running Windows. A fancy GUI > application will then present this to the operator. A similar link is > necessary in the other direction for signal injection. > > The FPGA does some data processing, so we can't just buy a data > capture card. We may consider a capturing card to interface with the > FPGA digitally. > > So my question is: What's your recommendation for the PC-FPGA > communication? Given a fairly skilled engineering team and a > management that understands this is not a cheap quickie (but still > wants to keep costs and efforts at a minimum, of course) what would > you suggest? USB? PCIe? Ethernet? Capture data from debug pins? > Something else? I can recommend the FPGA modules from opal kelly. IMO they have a nice interface both on the HDL side and on the PC-side. They allow to easily upgrade from a USB connection to a PCIe connection, without too much changes. Personally I have only needed USB so far... Thomas (happy customer)Article: 153572
> >> If you use USB and standard drivers you should allow for at least 0.5 >> seconds of buffer on the FPGA (either direction). > > Is that still the case if you're using isochronous transfers, and making > sure that the PC is tuned for feeding your app? The problem is in tuning the (Windows) PC - you might ship the system running fine and then you get a call from the customer and the PC turns out to be running a load of other stuff that their IT department refuses to remove. It shouldn't happen but it does. We found the men with the cheque books usually sided with the IT department so it was better just to make it work whatever. Never got any joy at all with isochronous transfers - if the FTDI drivers support them it might be worth a go. Michael KellettArticle: 153573
On Thu, 29 Mar 2012 15:30:59 +0100, MK wrote: >>> If you use USB and standard drivers you should allow for at least 0.5 >>> seconds of buffer on the FPGA (either direction). >> >> Is that still the case if you're using isochronous transfers, and >> making sure that the PC is tuned for feeding your app? > > The problem is in tuning the (Windows) PC - you might ship the system > running fine and then you get a call from the customer and the PC turns > out to be running a load of other stuff that their IT department refuses > to remove. It shouldn't happen but it does. We found the men with the > cheque books usually sided with the IT department so it was better just > to make it work whatever. > > Never got any joy at all with isochronous transfers - if the FTDI > drivers support them it might be worth a go. > > Michael Kellett It depends on what the environment is, of course -- if the "PC" is embedded in an instrument or a machine, then you've got a much better chance of fending off a hypothetical IT department. I suppose that an overactive IT gnome might attempt to upgrade the Windows installation on a $50000 oscilloscope -- but I don't know if they'd try it a second time. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.comArticle: 153574
Gabor wrote: > Well, it took me about 5 minutes to code up a simple project with > a 32-bit counter and enough registers to prevent other logic from > being the worst-case path. In a XC3S50AN-5 there are enough rows > to keep 32-bits in a single carry chain. With no constraints, the > design built and reported 4.402 ns minimum clock period (after > place & route) or about 227 MHz. OK, thanks very much. The request was to run a counter at 100 MHz, and it sounds like this is doable. There are some concerns about crossing clock boundaries that need to be figured out, but it looks like it can be done. Thanks VERY much for doing the leg work on this! I've been learning how to set up a GUI for the project, the one area I really didn't know enough about. The FPGA part seemed simple except for the performance. Jon
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