Most things you can do with a custom ASIC chip you can do with an FPGA, except with slower clock speeds. High speed signal processing, massive parallel designs, custom anything pretty much. You can (and often do) even have processors inside the FPGA running software. Some real world applications include a lot of video encoding and processing, cellular stuff, electronic warfare and radar applications, self driving cars, and other high bandwidth and high speed custom data processing. Basically if you need a custom chip but don't need 10 million of them, FPGAs are a good choice.

Thanks. So like what do hobbyists use them for? Like why would you buy one to mess around with? And what is electronic warfare?

Some things a hobbyist might use one for:

* Experimental processor design. If you want to make a processor with its own custom instruction set, or modify an existing processor design, you need an FPGA to actually see it in action.

* Synthesizers and audio filters. You can do a lot of low latency signal processing compared to even a beefy microcontroller with an FPGA, so if you want to make your own synth sounds in hardware, an FPGA might make sense.

* Computer vision stuff. If you want to make some gadget that does some kind of image processing that is streaming from a camera, and FPGA would work, especially if you wanted it to be small/portable.

* High bandwidth or low latency SDR applications.

There's not much there for hobbyists past toy ISA design and basic digital logic design exercises unless you really stretch the definition of hobbyist. It's a steep increase in learning curve for power that most people will never use.

Electronic warfare is most commonly the disabling of enemy radio frequency equipment (radar, communications, targeting, etc).

Got it. So it sounds like this post is more for people looking to build products and choosing which FPGA to base them on.

A lot of people believe that the year of the "maker FPGA" is upon us, and that the only thing holding it back is bad vendor tooling, so there's a lot of HN posts about them as of late. The vendor tooling is bad, but more than anything, the use case just isn't there.

Given, this is just my opinion on the matter, so take it with a grain of salt.

Esoteric communication interfaces and situations where you want to address a lot of devices in parallel.

It's kind of a stretch, but take a wall of addressable LED strips like WS2812s as an example. Color data is sent along one wire as precisely-timed pulses, 1.25us per bit.

You can drive a few strips using critical sections written in assembly, or misusing SPI peripherals if your clock speed can easily divide into ~2.4MHz. But you'd be hard-pressed to run dozens of parallel LED strips with a good framerate.

On an FPGA, you can just write an "LED" module and add as many of those modules as you can fit into the chip. You can also decide whether to include a simple CPU in the design, or use another method of processing lighting patterns.

They're flexible, but they are also expensive enough that it's kinda hard to find somewhere that they make sense. A "cheap FPGA" price point of $50-150 is still an order of magnitude pricier than a cheap microcontroller board ($2-10).

Oh interesting. So basically instead of using 20 Arduinos I can make an FPGA into a custom LED driver where I hand it a bitmap and it communicates the image to the LED matrix? That sounds pretty neat.

Thank you for asking this question! Like you, I have some experience with microcontrollers and have lately been kinda curious about getting into FPGAs.

I learned some good perspectives from the replies to your query.