[agg23]

I _technically_ had prior knowledge as a computer architecture class had us stick some premade pieces together to create a CPU we designed, but I personally wrote no Verilog, and it was a small subset of the class.

I don't have much documentation for getting started with HDLs (Verilog, VHDL, etc), but I have tried to document my process as much as possible. I have primarily developed for the Analogue Pocket, so my documentation is themed towards that device, but there's IP (code modules) and wiki entries that would be useful for everyone: https://github.com/agg23/analogue-pocket-utils

I had previously written a cycle accurate NES emulator, so I was familiar with hardware techniques, but not what they look like in circuits. The first core I wrote was a schematic accurate Pong implementation. This was both good and bad because it's very simple and has no CPU (and thus no code), but it also makes it very hard to tell what is going on. I went from there to doing a lot of ports (NES, SNES, PCE, and a few more), and after that I worked on my own cores (Tamagotchi, Game and Watch). Tamagotchi I took a very typical software approach where I wrote massive amounts of unit tests and wrote against those tests. While this is what real hardware developers do, I found it to be a huge waste of time when you're working by yourself on a small project.

I, and a few others, are very willing to help people learn (though I'm still really a noob). If you want to play around in this space, let me know and I'll try to help you with what you need.

[agg23]

On the note of my sibling comment, a common book in this space for learning is "Designing Video Game Hardware in Verilog", which is specifically retrocomputing related.

[0xcafefood]

I second this book recommendation! I just started it exactly to get a foothold on FPGA programming. It's very accessible.

[lovelyviking]

with what FPGA hardware is better to start for first tries?

[Graziano_M]

The book actually has an accompanying emulator where you can run everything in browser!

[datameta]

My recommendation is the NAND2Tetris coursera course. You start with a single NAND gate and put together more complex gates building upon the previous abstraction. Part 1 covers things like creating Muxes, RAM, and an ALU in a stripped down HDL. Part 2 covers the software stack picking up after having created an assembler but I haven't taken it yet. Perhaps this is isn't tailor-made for jumping into FPGA fast but it helped fill in a lot of blanks for me coming from mostly software world.

[lovelyviking]

I really wish to play with those things because I was playing with hardware when I was a schoolboy and found it back then very entertaining.

I’ve built my first computer with soldering all the parts and then started debugging it with oscilloscope to see signals from chips and analyse them to find the problem. And in doing so I have quickly realised that I am missing something. This something was ‘How chips actually work’. Turned out it was called Digital electronics so I’ve decided to learn this on the way.

My treasure and source of inspiration at school time was this book: Digital Electronics by Roger Tokheim. I was dragging it to school and back every day just like people cary notebooks these days. This was my bible back then. Boys in the school made fun of me for this. The book was amazing and I think it still is.

I remember it all as very exciting time.

Now FPGA seems like a nice opportunity to revisit all of this after many years of programming and developing a new point of view about many paradigms.

May be you can direct me and others like me toward a good community and tips for shortening a learning curve. Possibly many things I am familiar with already and yet with FPGA I didn’t find a good/easy way to start so far. Perhaps you can advice something about ‘how’ and ‘were’ to begin.

[agg23]

This is retrocomputing specific, but this Discord server (https://discord.gg/3wv3gMhp) has quite a few of the big devs in the FPGA gaming space, and they're more than willing to answer questions. They're what really got me going after I built my Pong core.

I have always been a big advocate of learning while doing, especially in software. Find something, preferably small, that you want to build (your Pong), and work on making it a reality. Maybe it's making Snake entirely in HDL. Maybe it's playing around with LiteX on your preferred development platform so you can build something cool with the RISC-V processor (I don't suggest this though, start with learning a normal HDL). Maybe it's simply looking through one of the existing retrocomputing cores, trying to figure out how stuff ticks.

Until you get to the CPU design level, the general concepts you'll encounter will be fairly simple. I think it's enough to just play around with blinking lights, learning how parallel synchronous logic works, relative to how we think of software working.

[lovelyviking]

Thank you very much. I do prefer to start with small. This way I made whole emulation of my first computer showing assembler commands as it executes each operation and it was able to run original ROM successfully. It was a pleasure to observe. Hopefully I can reproduce it in FPGA to make the circle complete ;)

My challenge is to play with CPU designs at some point but in the beginning I agree it is easier to start with something like led blink, nand , register and then to other staff.

Is there some FPGA hardware you can advice to use for easy start? One that potentially(once I learn) capable to do let’s say UART or USB ? I do not know really how much of FPGA power required for those. Or it would be too big/expensive ? I can’t orient myself with this yet but I wish something physical to have for real motivation to ignite.

[agg23]

It really all depends on what you want.

It may sound like shilling, but the Analogue Pocket is actually an excellent development platform because it's everything all in one; you don't need to figure out how to take input, load data, or output to HDMI, because that's all taken care of you automatically. Now you pay for that in having a $200-250 price tag, plus ~$50-70 for your JTAG adapter, but I think it's excellent for starting.

For OSS, I would probably recommend a Lattice FPGA. Gowin FPGAs are really, really cheap (Tang Nano 9k), and _partially_ support an OSS toolchain, but it's missing many core components, and I've actually found bugs in the hardware (confirmed by others), so probably stay away.

The DE-10 Nano is very capable, though fairly sought after at this point. It has a decent amount of IO, and can run the MiSTer retrocomputing project, which has the largest collection of OSS cores out there.

----

However, probably before you even buy any hardware, play with simulations. Choose your HDL (Verilog is US focused, VHDL is EU focused) and choose a simulator. For VHDL, you can use GHDL and GTKWave for an entirely OSS setup. For Verilog, I would recommend downloading the closed source Intel ModelSim, but you can also produce very fast, C++ controlled simulations using Verilator.

In any case, start simulating and looking at waveforms. Debugging multiple sets of nets at once is a very interesting experience and is at the core of what you're doing when working with FPGAs (verification is something like 80-90% of the time), so you can learn a lot without any hardware just working on that. If you use Verilator, you can have psuedo LEDs or even a display to draw on.

[lovelyviking]

You gave very helpful and informative advice exactly what I’ve been looking for. I am very grateful to you and your efforts and hopefully others who wish to start with FPGA will find it as useful and perfectly guiding as I did. Thank you very much. You’ve made my day.