Reverse Engineering Lattice’s iCE40 FPGA Bitstream

Unlike microcontroller projects, projects involving FPGAs cannot yet claim to rely on a mature open-source toolchain. Each FPGA will, at some point, need to be configured with a proprietary bitstream produced from a closed source synthesis tool. This lack of a full FPGA toolchain to take your project from Verilog-or-VHDL to an uploadable bitstream is due to many reasons. First, writing such a “compiler” is complicated. It involves intimate knowledge of the resources available on the FPGA that can assimilate the functionality of the intended design. Second, the entire synthesis procedure is closed-source, a “secret sauce” of sorts for each FPGA vendor.

In response, [Alex] and [Clifford] have taken the first step towards an open-source toolchain for one FPGA; they’ve reverse-engineered the bitstream of Latttice Semiconductor’s iCE40 FPGA. The duo didn’t just pick the iCE40 on a whim. This choice was deliberately because that FPGA is available on a development board for a mere $22 so that others could follow in their footsteps without breaking the bank.

In the video below, [Clifford] demos the functionality of this new tool by synthesizing a design from Verilog to a bitstream and then back from a bitstream to Verilog. Given this feature, a staggering amount of work has been done towards developing a polished open-source toolchain for this particular FGPA.

To snag a copy of the latest code, have a look at its documentation page.

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The Oldland CPU 32-bit FPGA Core

Field Programmable Gate Arrays (FPGAs) let you program any logic you’d like onto a chip. You write your logic using a hardware description language, then flash it to the FPGA. You can even design your own processor and flash it to the chip.

That’s exactly what [jamieiles] has done with the Oldland CPU. It’s an open source 32 bit CPU core that you can synthesize for use on an FPGA. Not only can you browse through all the Verilog code in the Github repo, but there’s also a bunch of tools for working with this CPU core.

Included with the package is oldland-rtlsim, which lets you simulate the processor on a PC. The oldland-debug tool lets you connect to the processor for programming and debugging over JTAG. Finally, there’s a GNU toolchain port that lets you build C code for the device.

Going one step futher, [jamieiles] built a full SoC around the Oldland core. This has SPI, UART, timers, and more features you’d expect to find in a microcontroller. It can be flashed to the relatively cheap Terasic DE0-Nano board.

[jamieiles] has also ported u-boot to the processor, and the next thing on the list is the Linux kernel. If you’ve ever been interested in how CPUs actually work, this is a neat project to look through. If you want more open source CPU cores, check out OpenCores.

Using The Red Pitaya As An SDR

The Red Pitaya is a credit-card sized board that runs Linux, has Ethernet, and a good bit of RAM. This sounds a lot like a Raspberry Pi and BeagleBone Black, but the similarities end there. The Red Pitaya also has two RF inputs, two RF outputs, and a load of digital IOs, all connected to an Xilinx SoC that includes an FPGA. [Pavel] realized the Pitaya had all the components of a software-defined radio, and built an implementation to prove it.

The input for the SDR taps directly into one of the high impedance inputs with a simple loop antenna made out of telephone cable. The actual software-defined part of this radio borrows heavily from an Xilinx application note, while everything is controlled by either SDR# or HDSDR.

[Pavel] included a pre-built SD card image with all his software, so cloning this project is simply a matter of copying an SD card and building an antenna. The full source is also available, interesting if you would like to muck about with FPGAs and SDRs.

HDMI Audio and Video for Neo Geo MVS

[Charlie] was killing some time hacking on some cheap FPGA dev boards he bought from eBay. Initially, he intended to use them to create HDMI ports for a different project before new inspiration hit him. Instead, he added an HDMI port to Neo Geo MVS games. The Neo Geo MVS was a 90’s arcade machine that played gems like the Metal Slug and Samurai Showdown series. [Charlie] has a special knack for mods, being featured on Hackaday before for implementing Zork on hardware and making a mini supergun PCB. What’s especially nice about his newest mod is that the HDMI outputs both audio and video.

[Charlie] obtained the best possible video and audio signal by tapping the digital inputs to the Neo Geo’s DACs (digital-to-analog converter). The FPGA was then used to convert the signals to HDMI, maintaining a digital signal path from video generation to display. While this sounds simple enough, there was a lot that had to be done. The JAMMA video standard’s lower resolution was incompatible with the various resolutions offered by the HDMI protocol. [Charlie] solved this problem by implementing scan doubling using the RAM on the Cyclone II dev board. He then had to downsample the audio to 32kHz (from 55.6kHz) in order to meet the HDMI specs. Getting the sound over HDMI required adding data islands to the signal, a feat [Charlie] admits was a frustrating one.

When he tested the HDMI with his monitor, it was out of spec but still worked. His TV, on the other hand, refused to play it at all. This was due to the Neo Geo outputting 59.1 fps – not the standard 60 fps. Using the FPGA, [Charlie] overclocked the NeoGeo by approximately 1% and used the 27Mhz pixel clock to change the FPGA output to a 720 x 480p signal.

For those that love the scan lines of yore, they can be enabled with the push of a button. [Charlie] notes that there are some slight differences in the shadow effects of some graphics, but he has done his best to minimize them. He also admits that the FPGA code contributes only 100 microseconds of delay compared to analog output, which is fast enough for even the most hardcore gamers.

Check out the video after the break to see how the Neo Geo looks in HDMI along with a side-by-side comparison to a CRT TV.

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Reverse Engineer then Drive LCD with FPGA

Fans of [Ben Heck] know that he has a soft spot for pinball machines and his projects that revolve around that topic tend to be pretty epic. This is a good example. At a trade show he saw an extra-wide format LCD screen which he thought would be perfect on a pinball build. He found out it’s a special module made for attaching to your car’s sun visor. The problem is that it only takes composite-in and he wanted higher quality video than that offers. The solution: reverse engineer the LCD protocol and implement it in an FPGA.

This project is a soup to nuts demonstration of replacing electronics drivers; the skill is certainly not limited to LCD modules. He starts by disassembling the hardware to find what look like differential signaling lines. With that in mind he hit the Internet looking for common video protocols which will help him figure out what he’s looking for. A four-channel oscilloscope sniffs the signal as the unit shows a blue screen with red words “NO SIGNAL”. That pattern is easy to spot since the pixels are mostly repeated except when red letters need to be displayed. Turns out the protocol is much like VGA with front porch, blanking, etc.

With copious notes about the timings [Ben] switches over to working with a Cyclone III FPGA to replace the screen’s stock controller. The product claims 800×234 resolution but when driving it using those parameters it doesn’t fill the entire screen. A bit more tweaking and he discovers the display actually has 1024×310 pixels. Bonus!

It’s going to take us a bit more study to figure out exactly how he boiled down the sniffed data to his single color-coded protocol sheet. But that’s half the fun! If you need a few more resources to understand how those signals work, check out one of our other favorite FPGA-LCD hacks.

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Hacklet 28 – Programmable Logic Hacks

FPGAs, CPLDs, PALs, and GALs, Oh My! This week’s Hacklet focuses on some of the best Programmable Logic projects on Hackaday.io! Programmable logic devices tend to have a steep learning curve.  Not only is a new hacker learning complex parts, but there are entire new languages to learn – like VHDL or Verilog. Taking the plunge and jumping in to programmable logic is well worth it though. High-speed projects which would be impossible with microcontrollers are suddenly within reach!

fpga-hdmiA great example of this is [Tom McLeod’s] Cheap FPGA-based HDMI Experimenting Board. [Tom’s] goal was to create a board which could output 720p video via HDMI at a reasonable frame rate. He’s using a Xilinx Spartan 6 chip to do it, along with a handful of support components. The images will be stored on an SD card. [Tom] is hoping to do some video with the setup as well, but he has yet to see if the chip will be fast enough to handle video decoding while generating the HDMI data stream. [Tom] has been quiet on this project for a few months – so we’re hoping that either he will see this post and send an update, or that someone will pick up his source files and continue the project!

ardufpgaNext up is our own [technolomaniac] with his Arduino-Compatible FPGA Shield. Starting out with FPGAs can be difficult. [Technolomaniac] has made it a bit easier with this shield. Originally started as a project on .io and now available in The Hackaday Store, the shield features a Xilinx Spartan 6 FPGA. [Technolomaniac] made power and interfacing easy by including regulators and level shifters to keep the sensitive FPGA happy. Not sure where to start? Check out [Mike Szczys’] Spartan-6 FPGA Hello World! [Mike] takes us from installing Xilinx’s free tool chain to getting a “hello world” led blinker running!

lander3Still interested in learning about Programmable Logic, but not sure where to go? Check out [Bruce Land’s] Teaching FPGA parallel computing. Actually, check out everything [Bruce] has done on Hackaday.io – the man is a living legend, and a wealth of information on electronics and embedded systems. Being a professor of engineering at New York’s Cornell University doesn’t hurt either! In Teaching FPGA parallel computing, [Bruce] links to Cornell’s ECE 5760 class, which he instructs. The class uses an Altera/Terasic DE2 FPGA board to demonstrate parallel computing using programmable logic devices. Note that [Bruce] teaches this class using Verilog, so all you seasoned VHDL folks still can learn something new!

 

chamFinally, we have [Michael A. Morris] with Chameleon. Chameleon is an Arduino compatible FPGA board with a Xilinx Spartan 3A FPGA on-board. [Michael] designed Chameleon for two major purposes:  soft-core processors, and intelligent serial communications interface. On the processor side Chameleon really shines. [Michael] has implemented a 6502 core in his design. This means that it would be right at home as the core of a retrocomputing project. [Michael] is still hard at work on Chameleon, he’s recently gotten fig-FORTH 1.0 running! Nice work [Michael]!

Want more programmable logic goodness? Check out our Programmable Logic List!

That about wraps things up for this episode of The Hacklet! As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Robot Vision: Detecting Obstacles with FPGAs and line lasers

Somewhere down the road, you’ll find that your almighty autonomous robot chassis is going to need some sensor feedback. Otherwise, that next small step down the road may end with a blind leap off the coffee table. The first low-cost sensors we might throw at this problem would be sonars or IR rangefinders, but there’s a problem: those sensors only really provide distance data back from the pinpoint view directly ahead of them.

Rest assured, [Jonathan] wrote in to let us know that he’s got you covered. Combining a line laser, camera, and an FPGA, he’s able to detect obstacles that fall within the field of view of the camera and laser.

If you thought writing algorithms in software is tricky, wait till to you try hardware! (We know: division sucks!) [Jonathan] knows no fear though; he’s performing gradient computation on the FPGA directly to detect the laser in the camera image at a wicked 30 frames-per-second. Why roll up your sleeves and take the hardware route, you might ask? If we took a CPU-based approach at the tiny embedded-robot scale, Jonathan estimates a mere 10 frames-per-second. With an FPGA, we’re able to process images about as fast as they’re received.

Jonathan is using the Logi Board, a Kickstarter success we’ve visited in the past, and all of his code is up on the Githubs. If you crack it open, you’ll also find that many of his modules are Wishbone compliant, so developing your own projects with just some of these parts has been made much easier than trying to rip out useful features from a sea of hairy logic.

With computer-vision hardware keeping such a low profile in the hobbyist community, we’re excited to hear more about [Jonathan’s] FPGA-based robotics endeavors.

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