[yid]

Your comment represents some of the best of HN (detailed, illuminating, informative), but is incredibly depressing for someone with an idle curiosity in FPGAs. This is what I've long suspected, and it seems that the barrier to entry is generally a bit too high for "software" people.

[aseipp]

I do think there's some light at the end of the tunnel. IceStorm is a thousand times better than any of the existing EDA tools if you just want to learn, and has effectively done a full reverse engineering of the iCE40 series. It only has a Verilog frontend, but it's a great starting point.

You can get an iCE40 FPGA for ~$50 USD, or as low as $20. It'll take you probably 30 minutes to compile all the tools and install them (you'll spend at least 2x that much time just fucking with stupid, traditional EDA tools, trying to make sense of them, and you'll still do that more than once probably), and you're ready.

The learning material stuff is much more difficult... Frankly, just about every Verilog tutorial out there, IMO, totally sucks. And Verilog is its own special case of "terrible language" aside from that, which will warp your mind.

Did you just use an undeclared wire (literally the equivalent of using an undeclared variable in any programming language)? Don't worry: Verilog won't throw an error if you do that. Your design just won't work (??????).

If you're a "traditional" software programmer (I don't know how else to put it?) who's mostly worked in languages like C, Java, etc. then yes: just the conceptual change of hardware design will likely be difficult to overcome, but it is not insurmountable.

The actual "write the design" part hasn't been too bad for me - but that's because I don't write Verilog. I write my circuits in Haskell :) http://www.clash-lang.org -- it turns out Haskell is actually an OK language for describing sequential and combinatoral circuits in very concise way that embodies the problem domain very well -- and I have substantial Haskell experience. So I was able to get moving quickly, despite being 100% software person.

There are also a lot of other HDLs that will probably take the edge off, although learning and dealing with Verilog is basically inevitable, but I'd rather get accustomed to the domain than inflict self-pain.

MyHDL, which is an alternative written in Python, seems to be an oft-recommended starting point, and can output Verilog. Someone seems to even have a nice tool that will combine MyHDL with IceStorm in a tiny IDE! Seems like a great way to start -- https://github.com/nturley/synthia

[alain94040]

HDLs such as Verilog are fine when you keep in mind what the D stands for. They are not programming languages. They are hardware description languages. Languages used to describe hardware. In order to describe hardware, you need to picture it in your head (muxes, flops, etc.). Once you do, writing the HDL that describes that hardware is reasonably easy.

What doesn't work is using an HDL to write as if it were software. It's just not.

[0] I'm talking about the RTL subset obviously

[aseipp]

Sure, I don't think anything I said disagrees with that. This conceptual shift in "declarative description" of the HW is a big difference in moving from software to hardware design, and no language can remove that difference. It doesn't matter if you're using MyHDL or Haskell to do it! It just so happens Haskell is a pretty declarative language, so it maps onto the idea well.

But it's not just about that... Frankly, most HDLs have absolutely poor abstraction capabilities, and are quite verbose. Sure, it isn't a software language, but that's a bit aside from the point. I can't even do things like write or use higher order functions, and most HDLs don't have very cheap things like data types to help enforce correctness (VHDL is more typed, but also pretty verbose) -- even when I reasonably understand the compilation model and how the resulting design will look, and know it's all synthesizable!

On top of that, simply due to language familiarity, it's simply much easier for me to structure hardware descriptions in terms of things like Haskell concepts, than directly in Verilog. It wouldn't be impossible for me to do it in Verilog, though -- I'm just more familiar with other things!

At some level this is a bit of laziness, but at another, it's a bit of "the devil you know". I do know enough Verilog to get by of course, and do make sure the output isn't completely insane. And more advanced designs will certainly require me going deeper into these realms where necessary.

I've recently been writing a tiny 16-bit processor with Haskell, and this kind of abstraction capability has been hugely important for me in motivation, because it's simply much easier for me to remember, describe and reason about at that level. It's simply much easier for me to think about my 2-port read, 1-port write register file, mirrored across two BRAMs, when it looks as nice and simple as this: https://gist.github.com/thoughtpolice/99202729866a865806fd6d..., and that code turns into the kind of Verilog you'd expect to write by hand, for the synthesis tool to infer the BRAMs automatically (you can, of course, also use the direct cell library primitive).

That said -- HDL choice is really only one part of the overall process... I've still got to have post-synthesis and post-PNR simulation test benches, actual synthesizable test benches to image to the board, etc... Lots of things to do. I think it's an important choice (BlueSpec is another example here, which most people I've known to use it having positive praise), but only one piece of the overall process, and grasping the whole process is still something I'm grappling with.

[AlphaSite]

Out of interest, how does MyHDL compare to something like PyMTL?

https://github.com/cornell-brg/pymtl

[greendragon]

I haven't used PyMTL but have used MyHDL, years ago. (I'm glad for aseipp's comments because that proprietary mess is exactly why I haven't bothered keeping up with FPGA development, though IceStorm has gotten me interested...) Glancing at PyMTL it seems they're comparable -- neither require that much code (https://github.com/jandecaluwe/myhdl). I'd say without digging deeper MyHDL is older, stabler, better documented, and has been used for real world projects including ASICs. PyMTL might allow for more sophisticated modeling. I'd be concerned about PyMTL's future after the students working on it graduate, whereas MyHDL is Jan's baby.

Found http://ucsbarchlab.github.io/PyRTL/ which has a good overview of these sorts of projects.

[AlphaSite]

Thanks!

[dsabanin]

As someone who recently got into programming FPGAs from decades of usual software development, it's not that bad. Takes a totally different mindset, but it's much more approachable than what it seems to be.

Actually a couple of YouTube videos can get you up and running pretty fast. Verilog is quite simple and doing things like writing your own VGA adapter is pretty straightforward and teaches you a lot and is a lot of fun.

[RandomName2020]

Anecdote evidence, but I am currently learning FPGA and VHDL, and find it not more difficult than "normal" C. Way more more expressive, for sure: a complete 8 channel PWM controller under 150 lines. Parallelism without locking feels very cool.

[greendragon]

I think VHDL makes things easier. Verilog has some fundamental nondeterminism: http://insights.sigasi.com/opinion/jan/verilogs-major-flaw.h... Still, HDL in general is probably on the order of difficulty as getting used to pointers. If you've already done a bunch of work with breadboards and logic gates it's even easier to grok. Of course a lot of people just instantiate a CPU core on the FPGA and program in C...