Questions on Artix-7 boards

[ikanip]

Hi, I am looking to buy a board of the Artix-7 family and trying to choose one between Arty, Basys 3 and Nexys 4 DDR. I have the following questions.
1. Is it true that the Vivado software that comes with Arty can only be used for one year since Arty is an evaluation board?
2. Is it possible to install the Vivado software on different computers and work on them (using the same board)? Does this behavior differ in any way among the three boards mentioned above?
3. I am confused about the number of cells in Nexys 4. On Digilent's website, it says Arty & Basys 3 both have about 33K logic "cells", and Nexys 4 has about 16K logic "slices". How many logic "cells" does Nexys 4 have? Which one of these boards can support a larger design?
4. Why does Basys 3 cost more than Arty even though it has less features (like no ethernet, etc.)?

Looking forward to your response. This will help me to make a decision.

Thank you!

P.S.: I had earlier contacted Digilent through the "Contact US" link and asked these questions, but was told some of the questions were too technical, so I need to ask them in the forum. So please help!

[D@n]

1. There is no current limit to the time you can use the webpack license.  This license should be sufficient for all of the boards you list above.
2. Yes, it is possible to use Vivado for the same board across multiple computers--although if you have the board physically attached to one computer, you might experience differences.  (i.e., you can program the device from the computer to which it is attached)  You can install an identical webpack licensed installation on all three of your computers--(or 4, or 5, or ...)
3. If you look up Xilinx's 7-series overview, you can see how many logic cells and slices each of the various Artix-7 chips has (Table 2, top of page 2).  The Nexys-4 DDR has roughly 100k logic cells, whereas the Basys and Arty have roughly 33k.  The Nexys-4, therefore, is the more capable board.  I personally find the "slices" measure more useful: Each slice has 4 6-input lookup tables.  If your logic is simple, and you need two outputs from the same five inputs, then the 6-input lookup table can be re-arranged into 2 5-input lookup tables.  This may be what the "logic cells" is counting: the number of five input lookup tables on the chip, although I'd suggest this number is perhaps a touch inflated, as you may find it difficult to use all the look up tables as 5-input ones instead of 6.  (If this is confusing, just remember the Nexys-4 DDR has about 3x the capability of the Arty and Basys3)
4. I don't really know why the Basys3 costs more, but it may have something to do with all of the additional various hardware features that are on it.  These make for more wiring required to support the Basys3 than required for the Arty.
5. You might find this other discussion helpful as you consider your options.

 

Dan

[ikanip]

Thanks Dan, that was pretty helpful. Would you have any recommendation among those three boards (or maybe something else) if I were to implement some kind of network protocol completely in hardware? For example, UDP or TCP (although TCP may be too ambitious because of its complexity, but it gives an idea of what kind of stuff I will be trying to do). This is just for self education (for future job interviews) and will not be part of any product (to be used commercially or otherwise). So performance is not of supreme concern but the board should still be able to support such a design.

Thank you!

[D@n]

Recommendations ... sure!

1. Don't get the Basys-3.  It doesn't have a network connection, and although Digilent offers a network PMod, it's only supported on the PIC chips.  (This doesn't mean it's a bad board--just that it won't do network stuff.)
2. The Nexys4 DDR is probably overkill.  I say probably because I don't have one, because it's more expensive than the Arty and because ...
3. The Arty should work just fine for the task.  I say this because the demo application on the Arty is a web server.  Sure, it uses MicroBlaze, but ... that is TCP, now, isn't it?

Some things you might wish to check out: @hamster has an Arty  board, and he's taught his how to send UDP packets without any software.

I'm also trying to do some Arty work as well.  My project is by no means complete today, but feel free to check out the link and see some of work so far, and the goals I am trying to accomplish..

Dan

[ikanip]

Thanks Dan for the recommendation and the links. I will probably go with the Arty then. One more question. Which one of these boards is the best for hooking up to a monitor (through VGA, for example) if I designed some graphics type stuff (like games)? I read the other post that you had sent a link for earlier. You mentioned that the Basys-3 does have VGA but its RAM size is too low for a reasonable sized frame buffer. And Arty doesn't have VGA, right? Is there any option of connecting an Arty to VGA? And how about the Nexys4?

Checked out your projects as well. Very cool stuff! You mentioned the goal is to use it as an NTP server. Are you using it for any other type of application currently?

[D@n]

You are correct: I would not recommend the Basys-3 board for any graphics application such as Video games.  That said, @Bianca did surprise me by telling me that she managed to get a Pacman game running on it ... so it's not impossible. 

The Nexys4 DDR has a VGA output as well as more memory (128MB) then the Basys-3, and so I think it has the capability for doing video work such as video games.  (I haven't tried it to know ...)  Although if you are seriously interested in Video, you should also check out the Nexys Video. That's also got an ethernet port--but this one goes up to GigE, as well 512MB memory and an HDMI output instead of a VGA output.  The Nexys-Video also has twice the logic of the Nexys-DDR.  I guess it all depends upon what you need and what you are looking for.

Moving on to the Arty, you are correct--the Arty does not have a video output.  Could you run graphics over VNC?  Sure--it'd be quite a project though.  Could you solder up a connection to a VGA?  I suppose.  I've never done it, though, so I can't really comment on how feasable it is.

As for my own Arty project, ... No, I'm not using it for any particular application ... yet.  If you are interested in suggesting one, feel free to open a private chat and we can talk further.  I've got a software loader that I haven't yet ported to the board, but would probably only take me an hour to do or so.  Otherwise, I might end up being stuck working on the memory interface for a while.  I was a bit disappointed to discover Xilinx's Memory Interface Generator produced a memory solution with roughly a 23 clock latency from a memory interface that has only a 9-clock latency.    While accessing it via a pipelined mode can mitigate this ... shortcoming, I'd really like to see it do better.  So we'll see what I discover as I dig farther into this project.  (That's been today's task ... again.  Incidentally, the network interface is waiting on the memory interface to complete ...)

Dan

[Bianca]

@ikanip, If you have a large budget you can try Nexys4-DDR or Nexys Video, as @D@n said. They are very capable and can help you learn and develop your projects. However, if the budget is a problem and you are not able to invest in an expensive board and you are not definitely decided for Artix-7, I suggest you to take a look at the Zinq board (ZYBO). It has VGA, Ethernet, 4 user leds, switches and buttons. It also has HDMI and audio. The board is equipped with a Zynq-7000 which has besides the FPGA an ARM processor.  

Every board is nice to work with and it's an experience. I would recommend Basys3 for beginners, you you're just starting with FPGA and don't want very complicated projects. It's an amazing board to start with and learn about VGA and FPGA. If you want communications and you're not very interested in video, Arty is the solution. If you need both you can look to Nexys4 -DDR and Nexys Video.However, if you want a challenging board with video and ethernet and maybe you are passionate and want to learn embedded Linux and use the ARM, you can try the Zybo.

In the topic Dan linked above, on his first response, we had a discussion about this boards with advantages and disadvantages. At the end you decide because you know that will suit you the best. 

Best regards,

Bianca