I intend to purchase an FPGA, development kit and I have looked at both the Xilinx and Digilent website. Both seem to have good development kits.
I have never worked with FPGA's before but have some experience working with microcontrollers.
I see that the entry level Spartan 6 boards are on a par in terms of price with the Spartan 3A/AN boards. I've not compared the features.
From your experience what development kit would you suggest Spartan3A/AN or Spartan6?
It looks to me like you still get a lot more to play with at a lower price point with Spartan-3. I found three different Spartan-6 options:
Of note here is that only the Atlys has a lot of on-board common I/O connectors, such as audio, video and keyboard. The LX16 kit has most of the interesting details on a Cypress PSoC instead, though it features a battery that may be interesting.
It boils down to what your intended projects are. With the lower budget Spartan-6 boards, you get an FMC-LPC connector that you can attach your own builds to; the LX16 kit also has a pin header, which is easier to get connectors for.
With the Spartan-3 kits, such as I have, we have a quite varied set of connections of more limited quality, and for major expansion there's the Hirose FX2 connector (again, somewhat unusual).
If your plan is to do video processing, I'd be very tempted to save up the extra money for the Atlys. It doesn't have very many expansion pins, but it has multiple on-board HDMI ports.
If you have never worked on FPGAs before, have you considered Altera FPGAs? Terasic makes some great ones with nice reference materials. You can check out www.terasic.com. Also I hear that Altera's Quartus environment is a lot more user-friendly than Xilinx's.
Also, the Altera university program is a great place for beginner tutorials. They start from the very beginning of "Hello World" type programs.
I would highly recommend going with a CPLD board first (something like this), or an Actel flash-based Igloo Nano, or something small like that. Big FPGAs can be kind of overwhelming, and they have so many pins it's quite time-consuming to get things hooked up properly. Plus, as soon as you want to integrate one into your design, you'll realize they come in very large packages, with dozens of power pins. Most of them require several voltages to operate at, not to mention that most FPGAs are SRAM-based, and not flash-based, so as soon as you disconnect power, they lose their design. So, you have to at least have an Active Serial Flash Memory chip wired up, but many people use sidecar CPLDs or microcontrollers to load designs onto the FPGA.
It's all very overwhelming. CPLDs, on the other hand, are great! They're usually single-supply operation, and if you want 5V-compliancy, you can still buy older Altera MAX 7000 chips. Plus they have on-board flash memory, so they don't need other components to bootstrap them. And CPLDs function more or less the same as FPGAs, so you program them by writing VHDL/Verilog, or using a schematic editor. Same jazz about clocking (remember to use crystal OSCILLATORS not crystals!), and same manner of programming over JTAG. CPLDs have far less logic elements than FPGAs, so you can't toss soft processors on them or do anything too crazy. But if you're just getting going, they're definitely the way to go -- and they cost a couple bucks each and come in big-enough packages that can be hand-soldered, which makes them practical to integrate into little projects you may have on your desk.
Another option is the low-end Flash-based FPGAs made by Actel. I've been recently playing around with the Igloo Nano Starter Kit, which is about $100. These devices are just big enough to fit an 8051 core on it along with some custom digital logic, so they're a great option when you're mixing program-flow states with custom logic.
S3 has been around a while so you'll probably find more options, and cheaper ones as used boards may be an option. If you're doing it with a view to making a product in the forseeable future stick with S3 until Xilinx get their act together on availability of newer parts. I also hear that the ISE software is getting flakier in later versions, so with S3 you can use an older. more stable version.
I have used a Spartan 3 in college, and the board had a vast array of connectors (of that age): PS2, VGA, DB9, and the classic pinheaders, plus some leds, 7segments displays, push-buttons and switches. That was more than enough for me.
PD: the simulator was SO huge that was better to "compile" the gates and test them on board.
I'm not sure about Digilent boards, but the Altera boards have full documentation as well as code demonstrations for every peripheral. its pretty easy to get started.
Something worth considering is the range of boards offered by Opal Kelly. There isn't much of a difference in price between their entry level Spartan 3 and Spartan 6 boards.
The big advantage we find with them is the on board USB support with associated HDL blocks for the FPGA and library code for your computer that makes it very easy to use.
If you'd like to do some breadboarding and hookup your own I/O devices (LEDs, 7-segs, buttons/switches, etc), while figuring things out for yourself (doesn't come with docs) you can get a 'barebones' mini FPGA board on eBay for around $50.
I picked up one of those and have been reasonably happy with it. I'll probably still end up getting a more full-featured board or make my own custom one someday, but for now this 'mini board' is fine for learning purposes.
