A Killer FPGA Playground with Real Silicon in Mind

Added: 2026-05-06

[00:00:04]What? And this shouldn't be happening.

[00:00:09]Uh what? Oh oh two bugs.

[00:00:13]>> [laughter] >> Simulation only gets you so far. You can run a zillion test vectors, throw formal methods at it if you're feeling fancy and can get it right, but none of that tells you what it actually feels like when a human presses the button, when a sensor starts talking asynchronously, or when that sneaky off-by-one error finally meets the real world. Now, what I'm showing today closes that gap. Now, testing on an FPGA isn't new, but doing it this way is up it's special. Now, whether you're targeting an ASIC or just want a great FPGA platform, here's why this matters. Now, for ASICs especially, the pain is real. Cuz once you tape out, you wait months.

[00:00:49]Now, whatever bad assumption slipped in through simulation is now baked into the silicon. Huh, what if you could run that exact design today on real hardware, real IO, real timing, using the same board, the same test benches, and the same interface your final ASIC will use?

[00:01:05]Now, that's the core idea behind the Fabric Fox FPGA breakout. It slots into the Tiny Tapeout demo board and turns it into a universal playground. Now, drop a bitstream, run the same one-line MicroPython command you'd use for an ASIC shuttle project, and you're live.

[00:01:20]The RP2 configures it automatically, exercises your test benches, and gives you full control while keeping the pinout and project interface 100% identical between FPGA and final silicon. Whether you're taping out your first ASIC, iterating an open-source core, teaching, or just want the fastest edit-run loop possible, this board closes that gap. So, how do you actually use it? Three steps. Harden one command locally, or just let GitHub actions do it for you. Get the bitstream onto the file system, load the project with a single enable call. That's it. You're running on real hardware. Seriously, it's that easy. If the GitHub action is doing it for you, example linked here, you just let it run.

[00:02:00]Then get the zip file and copy the bin over into bitstreams. That's it.

[00:02:06]You want to do it locally?

[00:02:07]Clone the TT support tools repo.

[00:02:11]Run TT FPGA harden.

[00:02:14]And it'll do its thing.

[00:02:17]Then, since you have the tools installed, you can make your life easier by getting them to handle the upload.

[00:02:23]And even tweak the config to set the default clock rate, so it's auto clocked just right whenever you enable the design.

[00:02:30]Five things that make this setup especially powerful. First, everything we did for ASICs just works here. Same switches, seven segment, external modules through the PMods, and the full MicroPython SDK. Second, it's one of the simplest FPGA boards I've made. And having no onboard flash, it doesn't just keep the bomb cost low, it means all your bitstreams live on the RP2 and are selectable instantly through the same shuttle interface. Just pick a project and it configures itself. Third, it acts as a universal chip. Every open-source design from previous Tiny Tapeout shuttles can run right now. Projects from way back to those waiting at the foundry this minute. Pick one, clone, tweak, play. I had my TT5 design running in minutes. Now, fourth, full interactive control via via the RP2. Use the REPL or Python scripts to poke inputs, read outputs, and monitor everything in real time. Fifth, hardware in the loop testing with MicroCoTB. Take your existing CocoTB test bench and run it unchanged on real hardware. It's bundled in the SDK and incredibly valuable valuable for validation. And finally, if you're into graphics, the VGA playground lets you iterate visually in simulation, then gives you a bitstream for the FPGA with one click, so you can see it live on a monitor.

[00:03:43]Now, let's take a quick look at each one. Now, the whole point of Tiny Tapeout is to support many projects on a single chip, and the FPGA acts the same way with the same interface. From the REPL, you can access the shuttle and use tab completion to see what's around, select select projects with a single command, and swap it out for another just as easily. Plus, the RP2 is clocking the thing, so you can set the rate dynamically on a per-project basis.

[00:04:08]Speaking of projects, everything that's been on a Tiny Tapeout run is open source, which means even if you didn't get your hands on a physical chip, you can just find a good project, clone it, and get it running. To play with it, learn from it, try your own tweaks to it, whatever.

[00:04:22]And there are more projects available after every run. It's really amazing. I got one of my projects, the SHA-256 encoder from Tiny Tapeout 5 run, other people's projects that are still at the foundry, all of it is there for you available at any time. I found some old project, Flappy VGA by Daniel Robinson, from before we had the SNES gamepad PMod, updated it to have support for the controller in a few minutes, and now I can see just how bad I am at this game.

[00:04:52]Does anyone play this? Oh, yes.

[00:04:59]So, you have access to the internals with the source, and then from the outside, you have a whole MicroPython SDK, which lets you interact with the project, setting inputs, reading outputs through the REPL or Python scripting, which opens up a whole lot of options.

[00:05:13]On the RP2350 REPL, we have a TT object, which gives us access to all the IO, reset, and clock. I can drive inputs of the project as a group, one at a time, or in a Veriloggy way.

[00:05:26]Outputs can be read the same way, and this lets you figure things out through the terminal, then script whatever you want for automated interaction.

[00:05:33]Another really neat thing is if there's a CocoTB test bench for the design, yeah, you can just run it pretty much unchanged directly on the demo board.

[00:05:42]So, this is my CocoTB test bench. One of the biggest differences is right here, just importing MicroCoTB as CocoTB, so we don't have to do search and replace.

[00:05:52]The code itself is project-specific, but the point is this CocoTB test will be detected and do its thing when run. Now, its thing is regular CocoTB stuff, clocking the design, setting inputs, checking outputs, and asserting when it finds problems.

[00:06:07]In the REPL, you can just import the runner and run it.

[00:06:11]It finds all the tests and does the work.

[00:06:15]Here, it's checking my SHA-256 hasher, and things are going pretty well.

[00:06:20]By the end, you get a summary of all the tests and any errors that were reported.

[00:06:25]Having it run on the RP2 is definitely not the fastest way to do it, but it sure is simple. Nothing external to hook up or program, just bring in your test bench and go. Cool. I created MicroCoTB, which is an implementation of CocoTB that runs on basically anything with Python, including the RP2, and it's bundled with the SDK on every demo board. It's not the fastest thing in the world when running on the MCU, but it works, and the advantages of having your exact same test bench proving a physical design makes it well worth it. Now, you can find samples for that in the SDK repo, and I did a whole video about hardware in the loop if you're into that sort of thing.

[00:07:03]Finally, the last cool tool in the kit that I'd like to mention is for those who want to play with graphics, the VGA playground. It lets you tweak Verilog and see the output change live. It's a very cool way to iterate a design. And once you have all your settings just right, one button, boom.

[00:07:19]>> [clears throat] >> The thing is hardened, available to download, and ready for you to get running in real life. It's pretty neat.

[00:07:24]So, that's the Fabric Fox story. It gives you an incredibly fast, reproducible loop, simulation, real FPGA hardware, eventual ASIC, all on the same demo board with the same tools and code.

[00:07:35]No new expensive hardware, no rewriting your test benches, just drop a bitstream and go. Whether you're doing your first tapeout, teaching a class, hacking on open-source silicon, or just want the most fun and flexible Tiny Tapeout compatible board available, this is for you. Now, the breakout sold out, but we have a new batch brewing that you can get through the Tiny Tapeout store. See the guide link below for all the details and to try it out. I would really love to see what you built.

[00:08:00]Thanks for watching. Happy hacking.