vhdl

36 Articles

VexRISC-V Exposed

December 8, 2018 by 8 Comments

If you want to use FPGAs, you’ll almost always use an HDL like Verilog or VHDL. These are layers of abstraction just like using, say, a C compiler is to machine language or assembly code. There are other challengers to the throne such as SpinalHDL which have small but enthusiastic followings. [Tom] has a post about how the VexRISC-V CPU leverages SpinalHDL to make an extremely flexible system that is as efficient as plain Verilog. He says the example really shows off why you should be using SpinaHDL.

Like a conventional programming language, it is easy to find niche languages that will attract a little attention and either take off (say, C++, Java, or Rust) or just sort of fade away. The problem is you can’t ever tell which ones are going to become major and which are just flashes in the pan. Is SpinalHDL the next big thing? We don’t know.

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FPGA Calculator Uses Joystick

February 28, 2018 by 10 Comments

FPGAs are great fun, but sometimes you need a few starter projects under your belt. These projects might be something you could just as well do with a CPU, but you have to start somewhere. [LambdaPI] recently shared a 4-bit calculator created using an FPGA, and you can see it in the video below.

The calculator uses a Papilio FPGA board and a LogicStart accessory board for the display and switches. The Papilio normally uses schematic-based entry and Arduino code, but [LambdaPI] used VHDL. You enter the two 4-bit numbers on the 8 switches and then the joystick selects one of four operations (add, subtract, multiply, and divide).

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Apple II FPGA

October 10, 2017 by 20 Comments

[Stephen Edwards] had some time one Christmas. So he took a DE2 FPGA board and using VHDL built a pretty faithful reproduction of an Apple II+ computer. He took advantage of VHDL modules for the 6502 CPU and PS/2 keyboard, and focused more on the video hardware and disk emulation.

According to [Stephen], you can think of the Apple II as a video display that happens to have a computer in it. The master clock is a multiple of the color burst frequency, and the timing was all geared around video generation. [Stephen’s] implementation mimics the timing, although using more modern FPGA-appropriate methods.

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FPGA Clocks For Software Developers (or Anyone)

September 21, 2017 by 18 Comments

It used to be that designing hardware required schematics and designing software required code. Sure, a lot of people could jump back and forth, but it was clearly a different discipline. Today, a lot of substantial digital design occurs using a hardware description language (HDL) like Verilog or VHDL. These look like software, but as we’ve pointed out many times, it isn’t really the same. [Zipcpu] has a really clear blog post that explains how it is different and why.

[Zipcpu] notes something we’ve seen all too often on the web. Some neophytes will write sequential code using Verilog or VHDL as if it was a conventional programming language. Code like that may even simulate. However, the resulting hardware will — at best — be very inefficient and at worst will not even work.

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VexRiscv: A Modular RISC-V Implementation For FPGA

July 21, 2017 by 16 Comments

Since an FPGA is just a sea of digital logic components on a chip, it isn’t uncommon to build a CPU using at least part of the FPGA’s circuitry. VexRiscv is an implementation of the RISC-V CPU architecture using a language called SpinalHDL.

SpinalHDL is a high-level language conceptually similar to Verilog or VHDL and can compile to Verilog or VHDL, so it should be compatible with most tool chains. VexRiscv shows off well in this project since it is very modular. You can add instructions, an MMU, JTAG debugging, caches and more.

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Veni, Vidi, ViciLogic Teaches You Digital Logic Interactively

March 31, 2017 by 6 Comments

This is about the time of the year you realize you aren’t going to keep all of those new year’s resolutions you made. However, if one of them was to learn VHDL and FPGAs, you might be in luck. Vicilogic has a free course in Fundamentals of Digital Systems. You do have to register, but it didn’t even verify our e-mail address, so it shouldn’t be too onerous to sign up.

Associated with the National University of Ireland Galway, the training is high quality and offers animated demos in your browser of the digital circuitry. You can even control the demos yourself. You’d think the work was occurring in some browser script, but according to the site, the demos are tied to real FPGA boards. You can supposedly look in on them as you use them with a video stream, but we never saw that working so your mileage may vary. If you want a preview of what it looks like, check out the video below. There’s guided exercises and also quizzes where you have to interact with the demos.

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Printer Scrap Becomes FPGA Devboard

February 27, 2017 by 7 Comments

These days, if you want to start learning about FPGAs, it can be a daunting experience. There’s a huge variety of different platforms and devboards and it can be difficult to know where to start. [RoGeorge] decided to take a different tack. Like a 16-year-old drag racer, he decided to run what he brung – a printer control panel cum FPGA development board (Romanian, get your Google Translate on).

[RoGeorge] was lucky enough to score a couple of seemingly defective control panels from HP Laserjets discarded by his workplace. Seeing potentially good parts going to waste, like keypads and LCDs, he decided to investigate them further – finding a 50,000 gate Xilinx Spartan IIE running the show. Never one to say no to opportunity, [RoGeorge] dived in to learning how to work with FPGAs.

The forum posts are a great crash course in working with this sort of embedded FPGA platform. [RoGeorge] covers initial mapping of the peripherals on the board & finding a JTAG connector and programming solution, before moving on to basic FPGA programming and even covers the differences between sequential programming on microcontrollers and the parallel operation of FPGAs. Even if you don’t intend to get down and dirty with the technology, spend half an hour reading these posts and you’ll be far more knowledgeable about how they work!

In the end, [RoGeorge] showed how to teach yourself to work with FPGAs for the price of a couple of programming cables – not a mean feat by any means. It’s a testament to the hacker spirit, and reminds us of [SpriteTM]’s efforts in hacking hard drive controllers.