I too was skeptical of FPGAs until recently, I think you owe it to yourself to check out Zynq and Altera which combine FPGAs with ARM cores. The PL (FPGA part of these chips) can align the clock edges and write the data into the memory of the ARM processor. You might find it is possible to do the decimation in the PL saving the ARM for other things. You could potentially even generate UDP packets in the PL, if all you want to do is move the data someplace else. The infamous FPGA learning curve is quite real, but not insurmountable. There are lots of tutorials available, both from the vendors and from other sources.
> On May 28, 2020, at 5:50 AM, PAk Ys <[email protected]> wrote: > > Thank you TJF for that detailed answer and thank you too Andrew for your > insights. > > We are trying to extract radar data from one radar board. The goal is not > have it working at 50MHz (which is the system max rate), but have the > possibility if needed. Probably we will work at 10 to 20MHz, and the data on > the BBB is only sent via Ethernet to another device in the same network. We > only need to extract the data from the 4 Data lines (channels) whenever CLK > changes, the Frame line is only used to synchronized at the beggining since > the format doesn't change. > > We have already done this setup with DSPs and MCUs with Ethernet integrated > with no issues, however for my new design I only can use LVDS so a fast > device (like PRU) is needed. B eaglebone would give me much more flexibility > than a FPGA, because, I could decimate as you well said and/or implement a > simple radar data viewer on the ARM core. > > > > On Thursday, May 28, 2020 at 10:48:56 AM UTC+2, Andrew P. Lentvorski wrote: > What are you actually trying to do? That's a 50Mbit sustained transfer rate > if bit time is 20ns. 100Mbit if 10ns. And 4 channels. That's 200-400Mbps. > You're moving a *TON* of data even at slower clock rates--there is no > resource on the BBB that can keep that up very long. > > This seems quite questionable on the BBB ... even moreso if your timing > diagram is valid (which I suspect it is not). > > First, given your diagram, the sampling point would have to be recovered. > Note that the Clock, Data, and Frame are all coincident. Normally the clock > falls in the middle of the data window. That's not easy to recover without a > PLL. I doubt the BBB has enough resolution to hit the data stable point on > the data with any reliability at 50MHz. > > Second, are you *actually* running at 50MHz? Are you considering every > *cross* as the frequency (high-to-low on a single line) or are you > considering an individual signal rise-to-rise as the frequency. Is that data > changing every 20ns or every *10ns*? If it's 10ns, it's probably not > possible. > > I would *STRONGLY* recommend that you use an FPGA. Even an incredibly cheap > FPGA would deserialize that with ease and then you could put it into a form > in which you might be able abuse something like the RMII from the Ethernet > peripheral to transfer it out. > > But it's still a *LOT* of data. You need something that can handle gigabit > speeds if you keep this up even for a couple milliseconds. > > Your best bet would be to use that FPGA to also decimate the data as well so > that you're working with a reasonable amount of data. > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/d45e79ae-736d-42c3-abc1-765b0274a34c%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/d45e79ae-736d-42c3-abc1-765b0274a34c%40googlegroups.com?utm_medium=email&utm_source=footer>. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/3EA35A76-EE37-4AB5-A62D-04E560E3FEEC%40gmail.com.
