Beginer's FPGA with SERDES

Some hams want to work with FPGAs to generate high speed PN sequences in the
GHz range. LFSR designs are about as simple as you can get in an FPGA. The
only trick is getting the resulting signal out of the FPGA. Rather than
outputting a parallel word at some 100's of MHz into a shift register
clocked in the GHz range, it seems easier to use a SERDES to shift it out
directly from the FPGA.
But not all FPGAs have SERDES. Which are the lowest cost devices and the
easiest to use? By "easiest" I mean board level with a built in programming
interface so they just connect a USB cable and maybe power supply, no dongle
needed.
All the FPGAs I've worked with lately (by that I mean over the last 10
years) didn't include a SERDES.
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Rick C 

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rickman
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In Intel-land, the Cyclone IV GX and Cyclone V GX are the cheap transceiver devices - or the SX version if you also want an ARM core.
There are boards like:
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and with an ARM:
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I think the Lattice ECP5 also has transceiver support, though I haven't used it. For instance:
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(one thing to watch is any additional licences that may be needed)
The other question is: what do you want to connect it to? It's a GHz frequency signal, so you'll need to take care of signal integrity to get it anywhere. Therefore the connector format you intend to use may be important.
Theo
Reply to
Theo Markettos
The ham is using it as an analog signal, so he won't be caring about harmonics. It is a noise source for test gear, uniform over a wide bandwidth. I assume a ham can handle the analog aspects of the signal, lol.
Too bad that promo on the ECP5 board expired. I dug around a little and didn't find a SERDES on any of the Flash based parts by Lattice. I don't see any Altera boards with SERDES under $100. I guess if they are using the chip with the SERDES they figure you are going to use it with PCIe or similar, so the cost goes up.
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Rick C 

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While trying to dig through the Altera/Intel datasheets it seems they don't have the same sort of documents they used to have. Everything is broken up into many smaller manuals and most don't even have lead in information like a table of contents or intro page, it just starts with data! Is this an Intel thing?
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Rick C 

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rickman
No, the Altera site is pretty much the same as before the rebrand. They do two versions of documentation: one is the whole manual for the chip, sometimes split into a couple of volumes (eg vol1 internals, vol2 transceivers). Then the individual chapters are also available separately. When googling, the individual bits tend to rank higher - but when you want the whole document to read it's useful to know you can go to the device page and get the full PDF. Also worth bearing in mind there's lots of sharing - lots of features are the same across families, so no point duplicating info.
My point about connectors is that often transceivers come off on FMC or HSMC connectors - can your ham deal with those? You'll need a PCB, probably a 4 layer one if you're going more than a few mm.
Theo
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Theo Markettos
I wasn't able to find the usual info that is easily available on other makers' sites. They typically have a basic family manual that starts with the overview and a summary of the devices in the family and the available packages. This is followed by a high level description of the various aspects of the workings of the chip and finally electrical and mechanical data. Usually the fine points are covered in other manuals or tech notes. When I typed in "cyclone V datasheet" I got some hundreds of hits ranked by I assume relevance. Electrical specs came up first. I never found what I was looking for. I had to rely on the brief info on the web pages.
Yeah, the guy seems to be thinking of putting a 20 pin device on his own circuit board. I found a $30 Lattice FPGA board without SERDES for him, and they also have some parts in QFN and there's always the ever present 144 pin QFP. But he is talking about using ECL now. Whatever. Horse - water...
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Rick C 

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rickman
The starting point for Cyclone V docs is here:
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That seems to have what you suggest, just split over several manuals.
I haven't seen a device with transceivers that wasn't a BGA, so you might be in for trouble...
One option beyond the dev board is systems-on-module, where the FPGA is on a carrier board and all signals are pinned out to connectors. That converts the problem into interfacing with an FMC or similar connector. It isn't impossible to do that with careful design on a 2 layer PCB (and the cheap devices are max 3Gbps which isn't that fast), but do understand it won't be a case of just plugging in.
Theo
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Theo Markettos
Besides, it's an interesting type of a DSP problem. A case for which an m-sequence transform at the receiver side is an efficient solution.
Gene
Reply to
Evgeny Filatov
Evgeny Filatov wrote on 10/22/2017 6:02 AM:
I'm not sure what you are describing.
I remember learning about a photoacoustic spectrometer my professor was working on. It used a disk with slots to shutter the optical beam from a monochromator and self interfered by the disk making noise and vibrations. I wondered if that could be mitigated by making the slots in the disk different widths and detecting the acoustic signal in a synchronized manner. I wasn't schooled in electronics yet and didn't realize that is the basis of DSP techniques.
Is that the sort of thing you are talking about?
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Rick C 

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rickman
I don't believe he was serious about using an FPGA. He seems to be just talking about things and not so interested in anything that he can't build himself.
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Rick C 

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rickman
Not really. The type of setup you described can be used to measure impulse response of a system:
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Perhaps it's not what the ham is trying to achieve. Thought it's worth mentioning, though.
Gene
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Evgeny Filatov

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