Yosys Fronts For Xilinx ISE

We always marvel at how open-source tools can often outstrip their commercial counterparts. Yosys, the open-source tool for Verilog synthesis, is a good example. Although the Xilinx ISE design suite is something close to abandonware, a lot of people still use it because it supports older FPGAs the newer tools don’t. Its Verilog parser is somewhat slow to catch up to new standards, and according to a recent GitHub update, Yosys can now provide files for ISE that target Spartan 6, Virtex 7, and Series 7 FPGAs. In addition, there is some support for Spartan 3, Virtex 2, 4, and 5, although those are not ready yet.

According to the post, you’ll want to use the synth_xilinx command along with the -ise option and a -family option that matches your target (that is, xc6s for Spartan 6).  On the output side, you’ll write an EDIF file using the write_edif command.

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Laptop Like It’s 1979 With A 16-Core Z80 On An FPGA

When life hands you a ridiculously expensive and massively powerful FPGA dev board, your first reaction may not be to build a 16-core Z80 laptop with it. If it’s not, perhaps you should examine your priorities, because that’s what [Chris Fenton] did, with the result being the wonderfully impractical “ZedRipper.”

Our first impression is that we’ve got to start hanging around a better class of lab, because [Chris] came by this $6000 FPGA board as the result of a lab cleanout; the best we ever scored was a few old Cat-5 cables and some power strips. The Stratix FPGA formed the heart of the design, surrounded by a few breakout boards for the 10.1″ VGA display and the keyboard, which was salvaged from an old PS/2. The 16 Z80 cores running in the FPGA are connected by a ring-topology network, which [Chris] dubs the “Z-Ring”. One of the Z80 cores, the server core, runs CP/M 2.2 and a file server called CP/NET, while the other fifteen machines are clients that run CP/NOS. A simple window manager shows 80 x 25 character terminal sessions for the server and any three of the clients at once, and the whole thing, including a LiPo battery pack, fits into a laser-cut plywood case. It’s retro, it’s modern, it’s overkill, and we absolutely love it.

Reading over [Chris]’s build log puts us in the mood to break out our 2019 Superconference badge and try spinning up a Z80 of our own. If you decide to hack the FPGA-est of conference badges, you might want to check out what [Sprite_TM] has to say about it. After all, he designed it. And you’ll certainly want to look at some of the awesome badge hacks we saw at Supercon.

Thanks to [yNos] for the tip.

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.)

Chisel Away At FPGA Development

Most of the time if you were to want to develop for an FPGA, you might turn to Verilog or VHDL. Both of these are quite capable, but they are also firmly rooted in languages that are old-fashioned by today’s standards. There have been quite a few attempts to treat those languages as an output to some other tool — either a higher-level language or a graphical tool. One recent effort is a toolchain that starts with Chisel.

The idea behind Chisel is to provide Scala with Verilog-like constructs. If you want, you can use it as a “super Verilog” taking advantage of classes and other features. However, Chisel also allows you to create generators that produce different output Verilog depending on how you call them. True, you can do some of this with Verilog modules, but it is much easier with Chisel. Chisel uses Firrtl to convert what you ask it to do into Verilog for different FPGA and ASIC targets.

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Upgrading A MIDI Controller With An FPGA

While the “M” in MIDI stands for “musical”, it’s possible to use this standard for other things as well. [s-ol] has been working on a VJ setup (mixing video instead of music) using various potentiometer-based hardware and MIDI to interface everything together. After becoming frustrated with drift in the potentiometers, he set out to outfit the entire rig with custom-built encoders.

[s-ol] designed the rotary-encoder based boards around an FPGA. It monitors the encoder for changes, controls eight RGB LEDs per knob, and even does capacitive touch sensing on the aluminum knob itself. The FPGA communicates via SPI with an Arduino master controller which communicates to a PC using a serial interface. This is [s-ol]’s first time diving into an FPGA project and it looks like he hit it out of the park!.

Even if you’re not mixing video or music, these encoders might be useful to any project where a standard analog potentiometer isn’t accurate or precise enough, or if you just need something that can dial into a specific value quickly. Potentiometers fall short in many different ways, but if you don’t want to replace them you might modify potentiometers to suit your purposes.

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Hackaday Podcast 028: Brain Skepticism Turned Up To 11, Web Browsing In ’69, Verilog For 7400 Logic, 3D Printing In Particle Board

Hackaday Editors Mike Szczys and Elliot Williams cover the most interesting hacks over the past week. So much talk of putting computers in touch with our brains has us skeptical on both tech and timeline. We celebrated the 40th Anniversary of the Walkman, but the headphones are the real star. Plus, Verilog isn’t just for FPGAs, you can synthesize 7400 circuits too! Elliot is enamored of an additive/subtractive printing process that uses particle board, and we discuss a couple of takes on hybrid-powered drones.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Direct download (62 MB)

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Breathing LED Done With Raw Logic Synthesized From A Verilog Design

Breathing LEDs are an attractive adornment on many electronic devices. These days they’re typically controlled by software but of course there were fading effects back in the days of analog too. [Pepijn de Vos] mixes a little of the new and the old by building a hardware-based fader from a Verilog design and even too the time to explain the process in depth.

Rather than using a microcontroller and software, [Pepijn] wrote the logic required to make the LED “breathe” in the hardware description language, Verilog. You may be familiar with this for FPGAs, but using it to plan out a build with logic chips is just as apt a use. The Verilog was synthesized into a circuit using 74-series logic chips, with the help of work by [Dan Ravensloft] who has made a library for the Yosys Open Synthesis Suite. With the addition of a basic clock circuit, the LED is made to breathe and the rate can be controlled by changing the clock speed.

It’s a fun way to experiment with both Verilog and old-school logic, albeit one that may not scale well. An interesting side note from the Twitter thread, [Dan] estimates that with current settings the PicoRV32 CPU would require over 2000 chips to build. Regardless, it’s an interesting tool and one that likely has further scope for experimentation.

First patented by Apple way back in 2002, the breathing LED has been a popular project for those learning electronics. We’ve even seen it on motorbikes. Video after the break.

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