FPGA

369 Articles

The Bus That’s Not A Bus: The Joys Of Hacking PCI Express

February 3, 2021 by 55 Comments

PCI Express (PCIe) has been around since 2003, and in that time it has managed to become the primary data interconnect for not only expansion cards, but also high-speed external devices. What also makes PCIe interesting is that it replaces the widespread use of parallel buses with serial links. Instead of having a bus with a common medium (traces) to which multiple devices connect, PCIe uses a root complex that directly connects to PCIe end points.

This is similar to how Ethernet originally used a bus configuration, with a common backbone (coax cable), but modern Ethernet (starting in the 90s) moved to a point-to-point configuration, assisted by switches to allow for dynamic switching between which points (devices) are connected. PCIe also offers the ability to add switches which allows more than one PCIe end point (a device or part of a device) to share a PCIe link (called a ‘lane’).

This change from a parallel bus to serial links simplifies the topology a lot compared to ISA or PCI where communication time had to be shared with other PCI devices on the bus and only half-duplex operation was possible. The ability to bundle multiple lanes to provide less or more bandwidth to specific ports or devices has meant that there was no need for a specialized graphics card slot, using e.g. an x16 PCIe slot with 16 lanes. It does however mean we’re using serial links that run at many GHz and must be implemented as differential pairs to protect signal integrity.

This all may seem a bit beyond the means of the average hobbyist, but there are still ways to have fun with PCIe hacking even if they do not involve breadboarding 7400-logic chips and debugging with a 100 MHz budget oscilloscope, like with ISA buses.

Continue reading “The Bus That’s Not A Bus: The Joys Of Hacking PCI Express” →

Make Room For A New Arduino Competitor – With Native Brainf*ck!

January 12, 2021 by 70 Comments

With so many smaller and more capable microcontroller boards on the market it’s now fairly safe to say that the classic Arduino footprint and form factor is rather outdated. That’s not to say that there’s no fight left in the old contender though, and to prove it here’s a new platform in the familiar style set by the venerable Atmel-based board. [Eduardo Corpeño]’s Brainfuino is an Arduino competitor that runs everyone’s favourite esoteric programming language, Brainf*ck. (Keeping it SFW, folks.)

And in case you mistake it for a Brainf*ck emulator on a PCB then stand ready to be corrected, for this board runs the language natively in a Brainf*ck softcore on a Lattice MachXO2 FPGA. This is the real deal, on which only a true genius or masochist would dare to code.

The board itself is very neatly executed with a graphical style that presents more than a nod to the original Arduino. On this board is the FPGA, 256 kB ROM and 138 kB RAM, an STM32 to provide a USB serial port and an analogue input, and a level shifter to provide Arduino-style 5 V logic on the pins. We can see it’ll provide hours of fun to anyone interested in learning Brainf*ck, but besides that it has potential as an Arduino-shaped FPGA board. We like the joke, we like the graphical and engineering design, but underneath that lies quite the technical achievement.

Brainf*ck has made it to Hackaday before, not least in this jaw-dropping relay computer.

Edge-Mounted LEDs Make This Spherical POV Look Fantastic

December 18, 2020 by 19 Comments

For as many of them as we’ve seen, we still love a good persistence of vision display project. There’s something fascinating about the combination of movement and light creating the illusion of solid surfaces, and there’s always fun to be had in electromechanical aspects of a POV build. This high-resolution spherical POV display pushes all those buttons, and more.

Called “Flicker” for obvious reasons by its creator [Dan Foisy], this POV display started with a pretty clear set of goals in terms of resolution and image quality, plus the need to support animated images, all in a spherical form factor. These goals dictated the final form of the display — a PCB disc spinning vertically. The shaft has the usual slip rings for power distribution and encoders for position feedback. The PCB, though, is where the interesting stuff is.

[Dan] chose to use an FPGA to slice and dice the images, which are fed from a Raspberry Pi’s HDMI port, to the LED drivers. And the LEDs themselves are pretty slick — he found parts with 1.6 mm lead spacing, making them a perfect fit for mounting on the rim of the PCB rather than on either side. A KiCAD script automated the process of laying out the 256 LEDs and their supporting components as evenly as possible, to avoid imbalance issues.

The video below shows Flicker in action — there are a few problem pixels, but on the whole, the display is pretty stunning. We’ve seen a few other spherical POV displays before, but none that look as good as this one does.

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A Xilinx Zynq Linux FPGA Board For Under $20? The Windfall Of Decommissioned Crypto Mining

December 10, 2020 by 80 Comments

One of the exciting trends in hardware availability is the inexorable move of FPGA boards and modules towards affordability. What was once an eye-watering price is now merely an expensive one, and no doubt in years to come will become a commodity. There’s still an affordability gap at the bottom of the market though, so spotting sub-$20 Xilinx Zynq boards on AliExpress that combine a Linux-capable ARM core and an FPGA on the same silicon is definitely something of great interest. A hackerspace community friend of mine ordered one, and yesterday it arrived in the usual anonymous package from China.

There’s a Catch, But It’s Only A Small One

The heftier of the two boards, in all its glory.
The heftier of the two boards, in all its glory.

There are two boards to be found for sale, one featuring the Zynq 7000 and the other the 7010, which the Xilinx product selector tells us both have the same ARM Cortex A9 cores and Artix-7 FPGA tech on board. The 7000 includes a single core with 23k logic cells, and there’s a dual-core with 28k on the 7010. It was the latter that my friend had ordered.

So there’s the good news, but there has to be a catch, right? True, but it’s not an insurmountable one. These aren’t new products, instead they’re the controller boards for an older generation of AntMiner cryptocurrency mining rigs. The components have 2017 date codes, so they’ve spent the last three years hooked up to a brace of ASIC or GPU boards in a mining data centre somewhere. The ever-changing pace of cryptocurrency tech means that they’re now redundant, and we’re the lucky beneficiaries via the surplus market.

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Pushing The FPGA Video Player Further

November 30, 2020 by 4 Comments

A fact universally known among the Hackaday community is that projects are never truly done. You can always spin another board release to fix a silkscreen mistake, get that extra little boost of performance, or finally spend the time to track down that weird transient bug. Or in [ultraembedded’s] case, take a custom FPGA player from 800 x 600 to 1280 x 720. The hardware used is a Digilent Arty A7 and PMOD boards for I2S2, VGA, and MicroSD. We previously covered this project back when it was first getting started.

Getting from 800 x 600 to 1280 x 720 — 31% more pixels — required implementing a higher performance JPEG decoder that can read in the MPJEG frames, pushing out a pixel every 2.1 clock cycles. The improvements also include a few convenience features such as an IR remote. The number of submodules inside the system is just incredible, with most of them being implemented or tweaked by [ultraembedded] himself.

For the FPGA Verilog, there’s the SD/MMC interface, the JPEG decoder, the audio controller, the DVI framebuffer, a peripheral core, and a custom RISC-V CPU. For the firmware loaded off the SD card, it uses a custom RTOS running an MP3 decoder, a FAT32 interface, an IR decoder, and a UI based on LVGL.

We think this project represents a wonderful culmination of all the different IP cores that [ultraembedded] has produced over the years. All the code for the FPGA media player is available on GitHub.

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Hacking The FPGA Control Board From A Bitcoin Miner

November 18, 2020 by 49 Comments

For anyone serious about mining cryptocurrency such as Bitcoin, we’re well past the point where a standard desktop computer is of much use. While an array of high-end GPUs is still viable for some currencies, the real heavy hitters are using custom mining hardware that makes use of application-specific integrated circuits (ASICs) to crunch the numbers. But eventually even the most powerful mining farm will start to show its age, and many end up selling on the second hand market for pennies on the dollar.

Naturally, hackers are hard at work trying to find alternate uses for these computational powerhouses. While it won’t teach an old ASIC a new trick, [xjtuecho] has documented some very interesting details on the FPGA control board of the Ebit E9+ Bitcoin miner. Known as the EBAZ4205, this board can be purchased for around $20 USD from online importers and even less if you can find one used. Since it’s just the controller it won’t help you build a budget super computer, but there’s always interest in cheap FPGA development boards.

The Zynq SoC combines an FPGA and ARM CPU.

According to [xjtuecho], it takes a little bit of work to get the EBAZ4205 ready for experimentation. For one thing, you may have to solder on your own micro SD slot depending on where you got the board from. You’ll also need to add a couple diodes to configure which storage device to boot from and to select where the board pulls power from.

Once you’re done, you’ll have a dual core Cortex A9 Linux board with 256 MB DDR3 and a Artix-7 FPGA featuring 28K logic elements to play with. Where you go from there is up to you.

This isn’t the first time we’ve seen FPGA boards hit the surplus market at rock bottom prices. When IT departments started dumping their stock of Pano Logic thin clients back in 2013, a whole community of dedicated FPGA hackers sprouted up around it. We’re not sure the if the EBAZ4205 will enjoy the same kind of popularity in its second life, but the price is certainly right.

[Thanks to Rog77 for the tip.]

Proper Cassettes For Your FPGA Retrocomputer

November 10, 2020 by 53 Comments

You can tell the age of someone in our community with a simple question: what were the first removable data storage media you used? Punched cards for the venerable, cassettes for the middle-aged, floppies for the thirtysomethings, Flash cards for the twentysomethings, and maybe even “What’s a removable storage medium?” for the kids brought up on cloud services.  Even with refreshed interest in retrocomputing the cassette hasn’t made a comeback, but maybe that owes something to the hardware. Createing a cassette interface for an FPGA is a task that’s often overlooked, and that’s a project [zpekic] has tackled.

Cassette data recordings are frequency shift keyed, with the 0 and 1 of the binary information represented by different tones. An expected solution to detect these might be to use a Fourier transform, but instead he opts for a simpler solution of counting zero crossings and timing their interval. The resulting stream of data is fed into a UART from which the data itself can be reconstructed. All this is implemented on a Mercury FPGA board which contains a Xilinx Spartan 3A FPGA, but it’s a technique that could be used on other devices too.

So your FPGA retrocomputer deserves an authentic cassette interface, and now it can have one. We’d be especially impressed if all this 2020s wizardry could produce a more stable chuntey field, but we guess that might take a bit more work.

As a final aside, the project is dedicated to the memory of the pioneering Yugoslavian broadcaster [Zoran Modli], whose innovative 1980s radio show featured broadcasts of tape software for the computers of the time including our Hackaday colleague [Voja Antonić]’s Galaksija. Broadcasting software over the radio? That’s a cool hack.