On Sat, Jan 11, 2025 at 8:15 PM Corey Minyard <corey@minyard.net> wrote:
>
> On Sun, Jan 12, 2025 at 01:13:36AM +0000, Cameron Castillo via pacsat-dev wrote:
> > Hi Bill,
> >
> > Interesting presentation! A couple notes:
> >
> > On the FPGA design for the SDR, a significant amount of the work can be
> > done via Xilinx IP. I think the team has the idea that most of the DSP and
> > hardware would have to be built from scratch in verilog. For almost any
> > design today, many people use the block diagram editor from Xilinx instead
> > of writing their own verilog. Not only are these guaranteed to work but all
> > the driver code is also available in their software platform (Vitis). I've
> > looked into some of the DSP blocks they have available and the list is
> > fairly comprehensive (IIR/FIR filters, FFTs, Freq. Synthesizer to name a
> > few off the top of my head).
>
> Yes, I'm aware of this.  From what I can tell, the licensing is not open
> source on these.  If that's so we can't use them on our platform.  But
> maybe I'm wrong.

Also, for the record, you have all those same building blocks with a DSP.
Functions already exist to do pretty much everything you need.  So from
the point of view of building blocks available, I'd guess they are about the
same.  I think they are open source, but I need to double-check that.

I am biased towards a DSP because that's what I've used in the past, and
I recognise that.  But it really all comes down to:

1) Surviving the rigors of space.

2) Power usage

3) Open source

4) Accessibility - we want to build a platform that is easy for others to use.

I don't know FPGAs very well; I have done a little bit of VHDL and programmed
PALs (you probably don't even know what one of those is...) so for the analysis
I'm going to have to lean on others.

-corey

>
> Second, I am planning on custom modulation, so those would have to be
> written in VHDL or Verilog.  Not a show-stopper, though.
>
> >
> > One of the other benefits is that many of Xilinx's products have hard
> > integrated processors or have the ability to integrate soft processors (See
> > Zynq and MicroBlaze respectively). The nice thing about these is that they
> > support Linux development and bare-metal/RTOS configuration. We might even
> > be able to remove the TMS570 and replace it with one of the multi-core
> > devices. Perhaps we could have a system where Direwolf and the other
> > processing functions are run on the same chip as the DSP. The downside to
> > this is that I'm not sure how parallelable that would be (i.e. could we
> > maintain four Rx channels).
>
> If you are going to use something like a Zynq processor, why do you even
> need a DSP or an FPGA for this application? ;-)  You could even get
> those fancy Zynq processors that have built-in RF subsystems.  They just
> cost $2000 and need gobs of power.  I don't know much about the
> MicroBlaze, how powerful it is or whatnot.
>
> The big problem with these things is power.  Zynq or Versal is right
> out.  I'm looking to keep the entire power budget for everything outside
> of the PA to <1W.  I think I can be successful if I play some tricks.
> I have no idea how much a MicroBlaze on an FPGA would use.
>
> Also, there's a lot of functional safety things tied into the TMS570
> processors.  Things like lockstep processing, parity/ECC on everything,
> extended temperature, etc.  The MicroBlaze can do lockstep, it appears,
> meaning that it can't be superscalar and it will be slow.  I guess it
> says it's Harvard architecture.  I don't know how it would compare to a
> Cortex-R5F.
>
> >
> > I do a lot of work with Xilinx products and FPGAs at work. It's mostly for
> > video functions, but I've found it pretty easy to understand the
> > fundamentals of Vivado/Vitis in only a few months. With integrated
> > peripherals like AXI and the IP blocks, it probably wouldn't take as long
> > as everyone is thinking. I hardly ever touch verilog at work anymore...
>
> I'm not against using an FPGA, but it would take some research.  Do you
> have any idea of the power they would use?
>
> >
> > As far as the amplifier project is coming, I'm back in the lab at work and
> > want to get some more prototyping done with our actual amplifier. Does
> > anyone on the team have extra stock of the transistor we're using for the
> > Tx amplifier (ATF05MS004NT1)? I'd also like to get an inductor kit like this
> > one
> > <https://www.amazon.com/First-Inductor-Assorted-1nH-270nH-42Valuesx50pcs/dp/B074QM4HNP>
> > as
> > the one I have at work is all 0201s and I can't reliably solder it...
>
> A book of inductors :-).
>
> >
> > On that note, I'm happy to keep prototyping it if the team wants to go in
> > that direction, but I think it'd be faster to go with a premade power amp.
> > I've already created a schematic for a PA as a backup to the work I'm doing
> > now. If we want something for Jim's test board, I could probably get
> > something to at least prototype with a lot sooner even if we think we could
> > do better with the discrete option. Just a suggestion.
>
> Are you talking about a PA module as something that can be used on the
> satellite, or just something as a temporary solution to plug into Jim's
> board?  And as I mentioned before, power is a big issue.  I don't know
> much about these things, though.
>
> Thanks,
>
> -corey
>
> >
> > Thanks,
> >
> > Cameron Castillo
> >
> >
> > -------------------------------------------------
> >
> > Cameron Castillo
> >
> > KJ7ILB
> >
> > *P*: (503) 752-8877
> >
> > --------------------------------------------------
> >
> >
> > On Fri, Jan 10, 2025 at 8:47 AM Bill Reed <bill@brconnect.com> wrote:
> >
> > > This is a better URL...
> > >
> > > https://github.com/AMSAT-NA/PacSatDocs/blob/main/SDR/MinyardSDR_1-9-2024.webm
> > >
> > > -------- Forwarded Message --------
> > > Subject: Last nights recording
> > > Date: Fri, 10 Jan 2025 09:31:07 -0600
> > > From: Bill Reed <bill@brconnect.com> <bill@brconnect.com>
> > > To: Cameron Castillo <camstillo2000@gmail.com> <camstillo2000@gmail.com>
> > >
> > > We discussed 2 things last night.
> > >
> > > 1: Start of SDR development to replace AX5043.  Exciting stuff!
> > >
> > > https://github.com/AMSAT-NA/PacSatDocs/SDR/MinyardSDR_1-9-2024
> > >
> > > 2: Discussion of 2025 budgets that haven't been approved yet. More to
> > > come....no video.
> > >
> > > I would like to discuss your project with you at some point.  Can it be
> > > prototyped on the new launchpad that Jim is working on?
> > >
> > > Bill
> > >
> > >
>
> >
> > -----------------------------------------------------------
> >
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