FPGA

373 Articles

Symbiflow Open Source FPGA Toolchain

November 1, 2019 by 12 Comments

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

October 28, 2019 by 17 Comments

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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“The Thing”: A Homemade FPGA Board

October 17, 2019 by 13 Comments

The Thing is an unassuming name for an ambitious project to build an FPGA board from easy to find components.

The project stems from an earlier build submitted to the 2018 Hackaday Prize by [Just4Fun] where two dev boards – an STM32-based Arduino and an Altera MAX II CPLD board – were combined with the Arduino used as a stimulus generator for the CPLD. This way, the Arduino IDE, interfaced through USB, can be used for programming the CPLD.

The Thing similarly uses the STM32 Arduino as a companion processor for the FPGA, with a 512KB SRAM and common I/O for GPIOs and a PS/2 keyboard for running HDL SOCs. It can also run Multicomp VHDL SOCs, a modular design that was made to run some older 8-bit CPUs made by [Grant Searle].

The FPGA (EP2C5T144C8N) uses the Quartus II IDE for configuration with a USB Blaster dongle through the JTAG or AS connector. The FPGA side controls a 4 digit seven segment LED display, four push buttons, 3 LEDs, a push button to clear all internal FFs (sampling rates), a push button to force a reboot (configuration reload), and a switch to force all pins to Hi-Z mode. Both an onboard 50MHz oscillator and connector for an external oscillator are also present on the FPGA side.

In one demo of the MP/M system capability of the board, The Thing was made to handle four concurrent users with one serial port connector to a PC and terminal emulator and the other serial ports connected to terminal emulators on VT100 boards routed through a dual-channel RS232 adapter board.

Both the Arduino and FPGA sides can also be used as standalone boards, but why use one when you can harness both boards together?

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Upgrading A MIDI Controller With An FPGA

September 29, 2019 by 16 Comments

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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LED Driver Board Could Be Your Ticket To FPGA Development

August 15, 2019 by 19 Comments

Microcontrollers are a great way to learn about developing for embedded systems. However, once you outgrow their capabilities, FPGAs bring muscle that’s hard for even the fastest-clocked micros to match. If you’re doing anything with high-speed signals, loads of RAM, or something that requires lots of parallel calculation, you can’t go past FPGAs. Dev boards can be expensive, but there are alternatives. There’s a nifty project on Github trying to repurpose commodity hardware into a useful FPGA development platform.

Chubby75 is a project to reverse engineer the RV901T LED “Receiver Card”. This device is used to receive signals over Ethernet, and clock data out to large LED displays. This sort of work is highly processor intensive for microcontrollers, but a cinch for FPGAs to manage. The board packs a user-reprogrammable Spartan 6 FPGA, along with twin Gigabit Ethernet ports and 64MB of SDRAM. Thanks to the fact that its firmware is not locked down, it has the potential to be repurposed into all manner of other projects. The boards are available for under $30 USD, making them a prime target for thrifty hackers.

Thus far, the team have begun poring through the hardware documentation and are looking to develop a toolchain to allow the boards to be easily reprogrammed. With the right tools, these boards could be the next thing in cheap FPGAs, taking over when the Pano Logic thin clients become thin on the ground.

[Thanks to KAN for the tip!]

The March Toward A DIY Metal 3D Printer

July 26, 2019 by 20 Comments

[Hyna] has spent seven years working with electron microscopes and five years with 3D printers. Now the goal is to combine expertise from both realms into a metal 3D printer based on electron-beam melting (EBM). The concept is something of an all-in-one device that combines traits of an electron beam welder, an FDM 3D printer, and an electron microscope. While under high vacuum, an electron beam will be used to fuse metal (either a wire or a powder) to build up objects layer by layer. That end goal is still in the future, but [Hyna] has made significant progress on the vacuum chamber and the high voltage system.

The device is built around a structure made of 80/20 extruded aluminum framing. The main platform showcases an electron gun, encased within a glass jar that is further encased within a metal mesh to prevent the glass from spreading too far in the event of an implosion.

Vacuum chamber enclosed in mesh (new gasket shown)
Mold for making silicone gasket

The design of the home-brewed high-voltage power supply involves an isolation transformer (designed to 60kV), using a half-bridge topology to prevent high leakage inductance. The transformer is connected to a buck converter for filament heating and a step up. The mains of the system are also connected to a voltage converter, which can be current-fed or voltage-fed to operate as either an electron beam welder or scanning electron microscope (SEM). During operation, the power supply connects to a 24V input and delivers the beam through a Wehnelt cylinder, an electrode opposite an anode that focuses and controls the electron beam. The entire system is currently being driven by an FPGA and STM32.

The vacuum enclosure itself is quite far along. [Hyna] milled a board with two outputs for a solid state relay (SSR) to a 230V pre-vacuum pump and a 230V pre-vacuum pump valve, two outputs for vent valves, and inputs from a Piranni gauge and a Cold Cathode Gauge, as well as a port for a TMP controller. After demoing the project at Maker Faire Prague, [Hyna] went back and milled a mold for a silicone gasket, a better vacuum seal for the electron beam.

While we’ve heard a lot about different metal 3D printing methods, this is the first time we’ve seen an EBM project outside of industry. And this may be the first to attempt to combine three separate uses for an HV electron beam into the same build.

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XFM: A 32-Voice Polyphonic FM Synthesizer On An FPGA

July 24, 2019 by 27 Comments

There’s something about Frequency Modulation (FM) synthesizer chips that appeals to a large audience. That’s one of the reasons behind [René Ceballos]’s XFM project, aiming to duplicate on an FPGA the sound of pure-FM synthesizer chips of the past such as the Yamaha DX series, OPL chip series and TX81Z/802/816. The result is a polyphonic, 32-voice, 6-operator FM synthesizer stereo module.

The project page goes into a lot of detail about the design choices which ultimately led to XFM being implemented on an FPGA, instead of using a dedicated DSP or MCU. Coming from the world of virtual synthesizers running on PCs, [René ]’s first impulse was to implement something on a Raspberry Pi or equivalent. Unfortunately these boards require a lot of power (ruling out battery-powered operation) and can hardly be called real-time, which led [René ] to abandon this attempt.

The design choice against the use of an MCU is simple: though capable of real-time processing, they lack the necessary power to make them a good choice for audio-processing. Working through the calculations to determine what kind of processing power would be needed, it was found that around 650 MIPS would be needed, a figure which most MCUs struggle to achieve a fraction of.

As one of the further requirements for XFM was that it should be as cheap as possible, this ruled out as too expensive the DSP chips which do have the power and hardware features needed. The component chosen was a Xilinx Spartan 6 FPGA, which though somewhat infamous and shunned in FPGA circles turns out to be a very economical option for this project.

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