Ice40 Runs DOOM

Spec sheets are an important tool in determining the performance of a given part or system, but they’re not the be all and end all when it comes to engineering. However, specs alone don’t prove whether a given system can complete a given task. Sometimes, you need to actually do the work to prove it instead – as [Sylvain] has done, running DOOM on the iCE40 FPGA.

DOOM’s minimum specifications demand a 386 with 4MB RAM minimum, but it’s commonly agreed that a 486 DX2 running at 66MHz with 8MB of RAM is required to play the game smoothly. With an iCEBreaker v1.0b running a RISC V softcore at 25MHz, it may seem like a difficult task, but the RISC V core has the benefit that many instructions run in a single clock cycle that take many on the 486. While the iCEBreaker doesn’t have much RAM onboard, it’s a simple job to piggyback an 8MB SPI device on top of the existing flash storage. Control of the game is via keystrokes sent to the iCEBreaker over serial, while video is handled over a PMOD video interface with an HDMI connector.

[Sylvain] does a great job of explaining all the minute details of the work that was required to get things working, and has provided files on Github for those keen to replicate the feat or expand upon the code. Music is notably absent but MIDI output could likely be achieved without much hassle. “Does it run DOOM?” is still a question asked of many platforms, even the new Nintendo Game & Watch. Video after the break.

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Mithro Runs Down Open Source FPGA Toolchains

Tim [Mithro] Ansell has a lot to tell you about the current state of open FPGA tooling: 115 slides in 25 minutes if you’re counting. His SymbiFlow project aims to be the GCC of FPGA toolchains: cross-platform, multi-platform, completely free, and all-encompassing. That means that it’s an umbrella framework for all of the work that everyone else is doing, from work on synthesis and verification tools, to placing and routing, to vendor-specific chip libraries. His talk catches you up with the state of the art at the end of 2019, and it’s embedded below. Spoiler alert: SymbiFlow has the big Xilinx 7-series FPGAs in its crosshairs, and is closing in. SymbiFlow is that close to getting a networked Linux system on the FPGA fabric in a Xilinx 7 today, completely independent of any vendor tools.

But let’s step back a sec for a little background. When you code for an FPGA, words you type get turned into a bitstream of ones and zeroes that flip perhaps a few million switches inside the chip. Going from a higher-level language to a bitstream is a lot like compiling normal programming languages, except with the twist that the resulting computational logic doesn’t map straight into a machine language, but rather into lower-level physical hardware on the FPGA. So “compilation” for FPGAs involves two steps: synthesis and place-and-routing. Synthesis takes the higher-level language that you write and turns it into a set of networks and timing requirements that represent the same logic, and can work across chip families. Yosys is the open-source synthesis tool of choice here.

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Symbiflow Open Source FPGA Toolchain

Anyone who’s ever had the pleasure of programming FPGAs knows that it’s a land of proprietary tools that almost require marriage level commitment to a specific platform to be effective. Symbiflow hopes to solve this by becoming the GCC of FPGAs.

Rather than a tool built around a specific chip or architecture, Symbiflow will provide a more universal interface.  Users can program in Verilog; architecture definitions define how the code will be compiled for the right chip. They are currently targeting the popular Xilinx 7-series, the very affordable iCE40 series from lattice, and the ECP5 FPGAs also from Lattice.

If you’re headed to Hackaday Supercon this year, [Timothy Ansell] will be giving a talk on how Symbiflow is making this process much more approachable and much less proprietary.  Overall we’re very excited about a common interface, especially as the price of FPGAs keep dropping into micro controller territory while also increasing in capability.

(Speaking of Supercon, and maybe this is a spoiler, the badge would not have been possible without Symbiflow, Project Trellis, Yosys, and NextPNR.)

ICEBreaker, The Open Source Development Board For FPGAs

The Hackaday Superconference is over, which is a shame, but one of the great things about our conference is the people who manage to trek out to Pasadena every year to show us all the cool stuff they’re working on. One of those people was [Piotr Esden-Tempski], founder of 1 Bit Squared, and he brought some goodies that would soon be launched on a few crowdfunding platforms. The coolest of these was the iCEBreaker, an FPGA development kit that makes it easy to learn FPGAs with an Open Source toolchain.

The hardware for the iCEBreaker includes the iCE40UP5K fpga with 5280 logic cells,, 120 kbit of dual-port RAM, 1 Mbit of single-port RAM, and a PLL, two SPIs and two I2Cs. Because the most interesting FPGA applications include sending bits out over pins really, really fast, there’s also 16 Megabytes of SPI Flash that allows you to stream video to a LED matrix. There are enough logic cells here to synthesize a CPU, too, and already the iCEBreaker can handle the PicoRV32, and some of the RISC-V cores. Extensibility is through PMOD connectors, and yes, there’s also an HDMI output for your vintage computing projects.

If you’re looking to get into FPGA development, there’s no better time. Joe Fitz‘s WTFpga workshop from the 2018 Hackaday Superconference has already been converted to this iCEBreaker board, and yes, the seven-segment display and DIP switches are available. Between this and the Open Source iCE toolchain, you’ve got a complete development system that’s ready to go, fun to play with, and extremely capable.

Programming A RISC-V Softcore With Ada

We were contacted by [morbo] to let us know about a project on the AdaCore blog that concerns programming a PicoRV32 RISC-V softcore with Ada. The softcore itself runs on a Lattice ICE40LP8K-based TinyFPGA-BX FPGA board, which we have covered in the past.

The blog post describes how to use the Community edition of the GNAT Ada compiler to set up the development environment, before implementing a simple example project that controls a strip of WS28212b RGB LED modules. There are two push buttons changing the animation and brightness of the lights.

The source can be found at the author’s Github repository, and contains both the Ada source and the Verilog source for the PicoRV32 softcore. To build the project one needs the GNAT compiler, as well as the open-source iCE40 development tools to compile the softcore.

There is a video demonstrating the finished example project, that we’ve placed below the break.

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Icestorm Tools Roundup: Open Source FPGA Dev Guide

We like the ICE40 FPGA from Lattice for two reasons: there are cheap development boards like the Icestick available for it and there are open source tools. We’ve based several tutorials on the Icestorm toolchain and it works quite well. However, the open source tools don’t always expose everything that you see from commercial tools. You sometimes have to dig a little to find the right tool or option.

Sometimes that’s a good thing. I don’t need to learn yet another fancy IDE and we have plenty of good simulation tools, so why reinvent the wheel? However, if you are only using the basic workflow of Yosys, Arachne-pnr, icepack, and iceprog, you could be missing out on some of the most interesting features. Let’s take a deeper look.

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Three Part Deep Dive Explains Lattice ICE40 FPGA Details

It is no secret that we like the Lattice iCE40 FPGA. It has a cheap development board and an open source toolchain, so it is an easy way to get started developing low-cost, low-power FPGA designs. There are a few members of the family that have similar characteristics including the top-of-the-line UltraPlus. [Steve] from Lattice and [Michael Klopfer] from the University of California Irvine have a three-part video series that explain the architecture of the devices. Altogether, the videos are about an hour long and — of course — they use the official tools, not IceStorm. But it is still a great time investment if you have an iCE40 board and you want to understand what the chip has under the hood.

The first part is fairly short and talks a lot about applications. There’s also a nod to the hobbyist use of FPGAs. Keep in mind that the iCE40 FPGAs come in different sizes and variants, so don’t get excited when you see them mention a RISC-V — that isn’t going to fit in your iCEStick, that we know of. The iCEstick has a HX-1K onboard, which is the high-performance variant with 1,280 logic elements, as opposed to the low-power (LP) version.

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