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.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

rickman <gnuarm@gmail.com> wrote:
> 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.

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:
http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=139&No=746
http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=830
and with an ARM:
http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=816

I think the Lattice ECP5 also has transceiver support, though I haven't used
it.  For instance:
http://www.latticesemi.com/Products/FPGAandCPLD/ECP5ECP5GPromotion.aspx

(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

Theo Markettos wrote on 10/21/2017 3:19 PM:
> rickman <gnuarm@gmail.com> wrote:
>> 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.
>
> 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:
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=139&No=746
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=830
> and with an ARM:
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=816
>
> I think the Lattice ECP5 also has transceiver support, though I haven't used
> it.  For instance:
> http://www.latticesemi.com/Products/FPGAandCPLD/ECP5ECP5GPromotion.aspx
>
> (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.

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.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

Theo Markettos wrote on 10/21/2017 3:19 PM:
> rickman <gnuarm@gmail.com> wrote:
>> 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.
>
> 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:
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=139&No=746
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=830
> and with an ARM:
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=816
>
> I think the Lattice ECP5 also has transceiver support, though I haven't used
> it.  For instance:
> http://www.latticesemi.com/Products/FPGAandCPLD/ECP5ECP5GPromotion.aspx
>
> (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.

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?

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

rickman <gnuarm@gmail.com> wrote:
> 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?

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

Theo Markettos wrote on 10/21/2017 6:24 PM:
> rickman <gnuarm@gmail.com> wrote:
>> 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?
>
> 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.

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.


> 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.

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...

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

rickman <gnuarm@gmail.com> wrote:
> 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.

The starting point for Cyclone V docs is here:
https://www.altera.com/products/fpga/cyclone-series/cyclone-v/support.html
That seems to have what you suggest, just split over several manuals.

> 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...

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

On 22.10.2017 0:04, rickman wrote:
> Theo Markettos wrote on 10/21/2017 3:19 PM:
>> rickman <gnuarm@gmail.com> wrote:
>>> 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.
>>
>> 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:
>> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=139&No=746
>>
>> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=830
>>
>> and with an ARM:
>> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=167&No=816
>>
>>
>> I think the Lattice ECP5 also has transceiver support, though I
>> haven't used
>> it.  For instance:
>> http://www.latticesemi.com/Products/FPGAandCPLD/ECP5ECP5GPromotion.aspx
>>
>> (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.
>
> 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.
>

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

Evgeny Filatov wrote on 10/22/2017 6:02 AM:
>
> 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.

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?

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

Theo Markettos wrote on 10/22/2017 5:55 AM:
> rickman <gnuarm@gmail.com> wrote:
>> 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.
>
> The starting point for Cyclone V docs is here:
> https://www.altera.com/products/fpga/cyclone-series/cyclone-v/support.html
> That seems to have what you suggest, just split over several manuals.
>
>> 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...
>
> 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.

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.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998