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Suggestions For Learning FPGA Development At Home?
Doug writes "I've recently been inspired to take up amateur electronics, specifically with FPGAs. I have an understanding of the basics, plus a solid programming background. From my research so far I've concluded that I should start with a simple FPGA development board and a couple of books on Verilog and/or VHDL and go from there. I found this Ask Slashdot discussion on Verilog vs VHDL very useful, but it focuses more on the development language rather than hardware. I'd be very interested in hearing peoples' recommendations for an entry-level kit that is simple, flexible, and affordable (sub-£200), and preferably Linux-friendly, and indeed any other wise words that experienced FPGA developers (professional or amateur) might have for a novice just starting out in the world of circuit design."
Unless you are very experienced designing with TTL chips, you won't get far in HDL without first getting good coverage of logic theory. My experience may be a little dated as it was 10 years ago that I started learning programmable logic, but at the time I enjoyed the first edition of Fundamentals of Digital Logic with VHDL Design. Not that logic theory has changed, but newer books might come with better examples or easier to use software. What I liked about that book was that it covered the theory in a very complete way while introducing the vhdl concepts at a manageable pace.
As far as development tools, they're overwhelmingly Windows based. You may have to run a VM so that you can use the most common tools (eg Xilinx WebPACK) until you're up to speed, then try a linux solution later. There are lots of hardware trainers out there - it's really not that important which one you use initially, although if whatever books you're reading have a recommended one, use that.
Your experience in the software world will help you somewhat, but be prepared for a vastly steeper learning curve than picking up a new programming language. There are not a lot of engineers who go very deep on both the software and hardware/logic sides - if you do you will end up with some valuable skills indeed. good luck!
Hardware: I highly recommend the Spartan Starter Kits. They're dirt cheap, well supported by the industry, and come with a good toolkit. There's not much more you need to know other than you'll probably want a serial cable in addition to the JTAG cable the kit ships with.
I'll grant you that the fabric isn't very large by today's standards, but it's still enough space to learn about the hardware. By the time you outgrow the fabric, you should have a good idea of what size hardware you want. In fact, your next board may even be a custom design based on a bus like wishbone. ;-)
Software: The Xilinx stuff (pronounced "Zy-Links") comes with a full toolkit for VHDL/Verilog development including an IDE, place and route tools, and software to reconfigure the FPGA. It's all quite slick and easy for a beginner to use.
Language: The most common route taken by new hardware developers is to learn Verilog. They do this because it's similar to C and that makes them comfortable. THIS IS A BAD IDEA. I can't count how many hardware designers swear up a storm when they see a Verilog project with loops and other software constructs stuck into them. See, the comfort and familarity of C makes new hardware developers forget that the hardware is a fixed layout. There is no for loops or control logic as you think of it. It all ends up flattening to hardware. If you write regular software constructs, you'll end up with the least efficient circuit possible.
From this perspective, learning VHDL is better because you won't have that comfort and familiarity that might tempt you into creating poor circuits.
I actually recommend doing some JHDL code for a while. It's lower level than VHDL, but that's a good thing. You have to think about every wire connection and how it all links up. When you're done, you can easily step through your circuit and see how it plays out in hardware. Even better, you learn how to properly use software constructs like loops to create a large number of static hardware objects. This will make your code better without falling in the trap of trying to write software.
That's my 2 cents anyway. Good luck! :-)
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Use Xilinx's FPGA Starter Kit. I bought the old version 5 years ago, and it also came with a CPLD dev kit. The dev tools run on linux too. It was something like $99 IIRC. It's made by Digilent. Last time I checked they had a better board for an extra $50 with an LCD display and 64MB SDRAM.
Otherwise, check fpga4fun.com . They use a tiny FPGA board, which reminds me of the Arduino: it has everything you need and nothing more.
I'd suggest Avnet Part # AES-SP3A-EVAL400-G, it's $49, and comes with everything you need for VHDL or Verilog...
I use these at work for general-purpose little widgets. They are great for all sorts of control/data collection devices. I think we've bought around 50 or so over the past couple of years.
Unfortunately, they do not support Linux.
There is an FPGA programming solution around for this board which does support linux (search for Nexys2 on comp.arch.fpga), but it does not support the data transfer function.
The data transfer function is very nice (under Windows). digilent supplies a driver and DLL, and I find it very easy to transfer data using Python. I do wish they supported Linux, though -- that's all I use at home.
Xilinx: http://www.xilinx.com/products/devkits/HW-SPAR3AN-SK-UNI-G.htm
Altera: http://www.altera.com/products/devkits/altera/kit-cyc3-starter.html
Both are very mainline FPGAs, both have full devkits, references designs, include the tools, linux support on Xilinx at least (not sure on Altera), and are both at your price point.
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VHDL for FPGAs and Verilog for ASICs. This rule applies everywhere except where it doesn't.
But in particular, I disagree with your reasoning about why to use VHDL vs. Verilog. Obviously, everybody's mileage may vary, but removing all vestiges of familiarity so that everything gets equally hard is not the way I learn.
The way I learned C was by looking at the assembly language output of the compiler, and you can effectively do the same thing with hardware.
It's not that hard to see what kind of logic your stuff compiles into -- in fact, you can dump a verilog netlist that shows you exactly how your logic maps to the internal chip elements. At a higher level, you can just look at the resource utilization report to see how "big" your circuit is.
In terms of the "right" language to learn for other reasons, apparently VHDL is somewhat more popular in Europe, and maybe somewhat more popular among FPGA-only designers, but all the "real" chip companies in the US use Verilog.
1. Get a (the) Spartan-3 starter board. It's got the 500 variant of the Spartan-3 on it which is big enough to implement even small processors. The board also has some very limited VGA output, and a heap of other things that makes it fun to work with (Serial I/F, etc). The manual for this board is one of the better ones for beginners, as well. I broke my own teeth on this board. It's 149 US schmucks from digilent.
2. Get Xilinx's free tool suite; its nicely compatible with that board. Free download from the web. Heck, you can even download and play with it without the / any board (but then you don't, of course, get the blinkenlights.) You can however try out and simulate designs before going to FPGA, and thus figure out why the (redacted) it doesn't (redacted) work. Simulations are your main way of verifying your design once you're past 20-odd gates.
3. Learn the HDL of your choice. Read the books. One warning only: it is NOT a programming language - the entire model in your head about how software works needs to be replaced. Case statements are king. Productivity with HDL's are generally way lower than software; don't be surprised by this.
4. Do points 1 through 3 in reverse order. Having a shiny 150 schmucker board won't help anything if you still have to spend two weeks grokking HDL's.
HTH.
For VHDL itself, I learned that with GHDL (VHDL front-end to gcc, though it hasn't been updated in a year now) and GTKWave for viewing the waves. Throw in make for a build system, and it was all I needed to design and implement (VHDL only, that is) a simple microprocessor.
That's a start anyway.
If you're tired of all the VHDL and Verilog nuances, try CtoVerilog.com
Learn how to use core generator and a simulator before you even buy a board. you only need a board when you actually want to have hardware.
Well, since most have already suggested the devkits of their choice (of which I have personally used at least a few), and which you could have come up with a Google search... I thought I'd rather advise on an excellent book (and which excellent cromulance you would not have been able to find with Google that easily): "VHDL Answers to Frequently Asked Questions" by Ben Cohen. Even though it has "FAQ" in the title, this books is actually an excellently structured textbook on VHDL. In fact, it's probably THE best book on VHDL for beginners and advanced beginners.
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Now that Xilinx has released new chips, the old ones are pretty cheap. A Spartan-3A evaluation board is less than US $200. These have VGA, PS/2, RS-232, a character LCD, a rotary encoder, LEDs, switches, and a bunch of extra connectors. The main problems are that the DDR2 RAM is *difficult* to use without a proprietary core, and the FPGA doesn't have access to the USB link.
Digilent Inc sells Spartan-3E boards for less than US $100. These have an easier-to-use DRAM and provide access to the USB port (though I think the official driver is windows-only, there seem to be solutions for using it on Linux).
Xilinx's ISE runs natively on Linux (RHEL, last time I checked). With a little searching, it was easy to figure out how to get it to work on Ubuntu, including the USB JTAG interface on the eval boards.
I haven't found a great book for learning this stuff. Pedroni's _Circuit Design with VHDL_ is okay, but it's not particularly deep and doesn't cover the FPGA development process at all. I had to study the Xilinx tutorials to get things working.
Writing HDL code superficially seems like normal programming, but it's not. Think of it as a way to translate your already-completed design into a form the computer understands. If you don't do the up-front design, it will be hard to fix through refactoring. The simulators just aren't up to the task. Restrict yourself to a single edge of a single clock, and things will be much easier.
I would recommend a board made by Digilent as they seem to have the greatest selection of add-ons and features plus their boards are high quality from my experience. As for the FPGA, I always recommend Xilinx because of the availability of free development tools, Linux support ( I currently have their WebPACK ISE running under Kubuntu 9.04 ) and the general superiority of their products, especially for projects that involve high speeds, a large number of gates and/or flip-flops eg. a microprocessor and even low power -- Xilinx' weakness has always been their relatively high standby/leakage current compared to other vendors, but they've significantly improved upon that with the Spartan-3A and the just released Spartan 6 chips.
As a Spartan 6 dev board is going to be expensive ( Xilinx' Spartan-6 FPGA SP601 Evaluation Kit is $295 and AFAIK it's the only entry level board currently available for that chip ) right now, I would recommend a Spartan 3A board. Specifically I would recommend Xilinx' Spartan-3A Starter Kit as it has the right amount of features for the price ( $189 ) and it's made by Digilent although if you're on a *really* tight budget you can get kits based off of this chip for as low as $49
jdb2
As many have stated, both Xilinx are Altera can be good routes. Note that while they Altera tools support Linux, their freebie Web edition does not, and the full kit is more than you'd want to spend. Any Xilinx starter kit should be fine for tooling around. I'm not sure your experience level, so I'll go with the basics...
I'm a young n00b in the FPGA world (two years design experience out of college now), so my experiences are pretty recent. I've got an EE degree, and would say first of all, get a firm grasp of logic design. Do you know what a flip flop actually is? Are you familiar with things like setup and hold time? If not, start out with a lot of reading. Horowitz and Hill's "The Art of Electronics" is a good standard...there's a lot of analog stuff that's "less relevant" to you, but there's a good section on digital design that's a great start.
One of my young programmer colleagues was looking over some of my code, and seemed to think it was pretty easy...the syntax seemed pretty straightforward, he liked the idea of combinatorial logic being so easy to implement, etc. He started tinkering himself, and VERY quickly realized that it was much more complex than he thought when issues of timing were thrown in. A fundamental knowledge of how signals are propagating through the device is key. It's not just PROGRAMMING, you're programming the actual hardware (or making fancy lookup tables, whatever. Get off my back!).
As designs get more complicated, you'll need to learn how to use some tools to analyze timings. Altera has Timequest, not sure what Xilinx uses. In college, I managed to get away with the bare minimum of analysis, but I consider this to be a flaw in my education...to do things right, you should do proper timing analysis.
I have an Altera starter kit I dink around with myself when I'm not at work, and it's definitely worth the time to learn the basics if you're an eternal tinkerer. Finally, the best advice I can give you...don't forget to use VIM as your editor, or you're just setting yourself up for failure.
Hardhack isn't a tag, it's a category. It stands for Hardware Hacking and is included by default. Try mousing over the story icon.
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This is a great site with a good bit of introductory information. I implemented their LED flasher tutorials when I was playing with my Xylinx Spartan board. fpga4fun.com
Actually, FPGAs are much more similar to hardware than they are to traditional software. Even though the configuration is volatile on most SRAM-based FPGAs, the "software" does not describe a set of procedural steps to perform as software does for microprocessors.
Rather, an FPGA configuration (personality), describes how the internal gates, storage elements, and interconnect is switched. This makes a configured FPGA almost indiscernible from an ASIC in function.
An FPGA isn't software loaded to "mimic" the functionality of an IC, it is software loaded to "describe" the functionality of the IC.
This is why VHDL and Verilog aren't strictly software programming languages. Rather, they are hardware description languages. Although they can be executed by software simulators in a fashion similar to software, they really describe hardware either behaviorally (procedurally or event-based) or structurally (netlist).
I write FPGA code for a living, more in VHDL than Verilog, and more for Xilinx than Altera.
I would actually recommend that you don't buy a board at first. You can pick one out so you can decide on a vendor's chip, that's fine, but simulate everything, because that's what HDL design is all about. Both vendors offer a free version of their toolset and there's a free simulator with each of those. Or you can download ModelSim Starter edition. I wouldn't call either one Linux friendly.
As far as the board goes, I would recommend one of Altera's Nios II Embedded Dev Kits. I feel that although Altera has a slightly steeper learning curve than Xilinx, they also have a nicer overall package than what Xilinx is currently offering. I'm speaking from the point of embedding a soft processor though, if that doesn't interest you, then either of the cheap Altera Cyclone or Xilinx Spartan kits will get the job done.
This is the only book you need on VHDL: The Designer's Guide to VHDL by Peter Ashenden.
I haven't found a Verilog book of similar quality.
Buy several books on Verification and testbench writing. That's where the real work comes in, and it's significantly more work than whatever circuit design you're doing. Spend the time to learn how to write self-checking testbenches.
Read over the Synthesis guides for whatever vendor's board you choose. Understand how the constructs you use affect synthesis. There's a wealth of information in the Xilinx and Altera online documentation. There's also a lot of really of good snippets of code which are themselves useful but also typically contrast less and more effective constructs for synthesis.
And finally, I will echo the caution that HDL is not a programming language, it is a design language. If you do not have a fundamental grasp of circuits, logic design, and computer architecture, I would recommend you pursue those topics first.
It is a little old, but the price is excellent... $150 for the general public, and $120 for students. Even though there are cheaper boards on the market, I have found that the combination of features at a low price has been pretty unbeatable, and it is also available from a lot of distributors.
Now, in the interest of full disclosure, I have been focused heavily on retrocomputing projects... they're a lot of fun.
Forget what you know about programming, FPGA's are about thinking in a compleltely different mind set
Yep. As a newbie a couple of years back I played around with both Altera and Xilinx's software, and found Altera's much more friendly, so I'm now an Altera-all-the-way kind of guy.
That said, Altera development boards can be a bit pricier than their Xilinx equivalents, mainly because they're harder to find (I don't know why, but perhaps Altera attracts a more advanced designer who doesn't need starter kits, etc, while Xilinx tends to attract the newbies?). That said, this board for around half the poster's budget limit boasts a last-gen (65nm) FPGA with about 20K logic elements, which will implement moderately complex designs, including a wide variety of microprocessor designs (the smallest I've seen uses less than 300LEs, so theoretically you could get about 70 of them on there...!), many of which can be run at ~50MHz on this hardware.
This really is not a task for programmers. It is a task for an engineer that has done both logic and software design. I've been programming FPGA's since Xilinx came out with their first chips. At the time, it was all schematic capture. Place and route never completed on its own, it always required user editing to finish. FPGA design techniques depend on your constraints. For some projects, it is much cheaper to buy a very large FPGA and not worry about space optimization. If you are building thousands of the same device, then space optimization is critical. For other projects, logic timing is everything. Every chip has it's own constraints as well, especially if speed is an issue. When speed is an issue, you have to really understand how your VHDL will be implemented, because it will make all the difference between sucess & failure. Learning how to use constraint files is important. Learning how to test using simulations is critical. Time spent writing and runing simulations may exceed design time for an order of magnitude.
I especially like Altera's "Nios Embedded Evaluation Kit" (aka the NEEK). It has its own TFT, sound codec, analog video input, ethernet and lots more. It also has a thriving uClinux community and they're working on including MMU support. Plus, you don't need a programming adapter for it - just put your hardware design on an SD card, insert into NEEK, power up, and off you go. Ok, it costs $449, but you can do far more than push a few buttons and let LEDs light up.
The AC's comments are valid and noteworthy nonetheless. Just because someone understands OOP and knows 5 software languages doesn't mean hardware hacking will be easy. The skills are related, but proficiency in one does not necessarily imply aptitude for the other.
I recommend two things. First, give up the notion that FPGA development as a hobby can be done for the price you're looking for. Good development boards are a little pricy, but you will frustrate yourself with no end in sight by using a barebones development kit. The best cheap dev kit I've seen yet is the Xilinx Spartan-6 SP601 kit. It includes everything you need to get started, including Xilinx ISE design software. That should set you back about $300. The Spartan-6 is fairly anemic in features and power compared to most other new FPGA's so a careful consideration of your goals should take place before you make a purchase.
Two, get a good FPGA development book. I highly recommend "Designing with FPGAs and CPLDs". It's a really useful primer on programmable logic hardware to those who already are technically literate.
http://books.google.com/books?id=enQq7m800xYC&dq=embedded+FPGA
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Spartan 6 is anaemic? What are you trying to build? I am working with a Raggedstone Spartan IIIe card (the mini-can); it's US$150 and I'm developing PCI hardware with it. That's hardly anaemic. There's lots of fun to be had with smaller devices as well.