Adding IceZero To The Raspberry Pi

[Kevinhub] noticed there were quite a few FPGA hats for the Raspberry Pi. Instead going out and buying one of these boards like a filthy commoner, he decided to spin up his own FPGA Pi accessory. This IceZero FPGA board combines the best features from other FPiGA boards, and does it in a form factor that fits right on top of the minuscule Pi Zero.

If you think slapping a Lattice FPGA onto a Pi has been done before, you’re right. Here’s a hat for the Pi using an iCE5LP4K-SG48, an FPGA with 3520 LUTs. The CAT Board from Xess has a slightly bigger FPGA with 7680 logic cells, and the FleaOhm has a monster FPGA on board that costs about $70 USD.

[Kevin]’s IceZero is at the lower end of these Raspberry Pi FPGA hats, using a Lattice ICE40HX4K. That’s only 3520 logic cells, but it only costs about $7 USD in quantity one. The board design is a standard two layer board that shouldn’t be too terrible for hand soldering. The boards are shared on OSH Park, should you want to test this little guy out.

This Pi Hat is specifically designed to be used with Project IceStorm, the Open toolchain for Lattice’s iCE40 FPGAs. That means there’s already a few projects out in the wild that can be easily ported to this platform, and already [Kevin] has a logic SUMP example going on his board.

Ice, Ice, Radio Uses FPGA

Building a software defined radio (SDR) involves many trades offs. But one of the most fundamental is should you use an FPGA or a CPU to do the processing. Of course, if you are piping data to a PC, the answer is probably a CPU. But if you are doing the whole system, it is a vexing choice. The FPGA can handle lots of data all at one time but is somewhat more difficult to develop and modify. CPUs using software are flexible–especially for coding user interfaces, networking connections, and the like) but don’t always have enough horsepower to cope with signal processing tasks (and, yes, it depends on the CPU).

[Eric Brombaugh] sidestepped that trade off. He used a board with both an ARM processor and an ICE FPGA at the heart of his SDR design. He uses three custom boards: one is the CPU/FPGA board, another is a 10-bit converter that can sample at 40 MSPS (sufficient to decode to 20 MHz), and an I2S DAC to produce audio. Each board has its own page linked from the main project.

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The Impressive Z80 Computer With The Unfortunate Name

We’ve seen a lot of retro builds around the Z80. Not many are as neatly done or as well-documented as [dekeNukem’s] FAP80 project. Before you rush to the comments to make the obvious joke, we’ll tell you that everyone has already made up their own variation of the same joke. We’ll also tell you the name is a cross between an old design from [Steve Ciarcia] called the ZAP80 and a reference to the FPGA used in this device.

[dekeNukem] says his goal was to create a Z80 computer without all the baggage of using period-correct support chips. You can argue about the relative merits of that approach versus a more purist build, but the FAP80 has a 5 slot backplane, VGA output, a PS/2 keyboard port and more. You can see one of many videos showing the machine below.

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FPGA Computer Covers A to Z

[F4HDK] calls his new computer A2Z because he built everything from scratch (literally, from A to Z). Well, strictly speaking, he did start with an FPGA, but you have to have some foundation. The core CPU is a 16-bit RISC processor with a 24-bit address bus and a 128-word cache. The computer sports 2 megabytes of RAM, a boot ROM, a VGA port and keyboard, and some other useful I/O. The CPU development uses Verilog.

Software-wise, the computer has a simple operating system, a filesystem, and basic programs like a text editor and an image viewer. Development software includes an assembler and a compiler for a BASIC-like language that resides on the PC. You can also run an emulator to experiment with A2Z without hardware. You can see a “car game” running on A2Z in the video below. You can also see videos of some other applications.

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Retro ZX Spectrum Lives a Spartan Existence

FPGAs (like Xilinx’s Spartan series) are great building blocks. They often remind us of the 100-in-1 electronic kits we used to get as kids. Lots of components you can mix and match to make nearly anything. However, like a bare microcontroller, they usually don’t have much in the way of peripheral devices. So the secret sauce is what components you can surround the chip with.

If you are interested in retro computing, you ought to have a look at the ZX-Uno board. It hosts a Spartan 6 FPGA. They are for sale, but the design is open source and all the info is available if you prefer to roll your own or make modifications. You can see a video of the board in action, below (as explained in the video, the color issues are due to the capture card trying to deal with the non-standard sync rate).

Here are the key specifications:

  • FPGA Xilinx Spartan XC6SLX9-2TQG144C
  • Static Memory 512Kb, AS7C34096A-10TIN
  • 50MHz Oscillator
  • Video output (composite)
  • PS/2 keyboard
  • Stereo audio jack
  • EAR jack connector (for reading cassette tapes)
  • Connectors for JTAG and RGB
  • Slot for SD Cards
  • Expansion port with 3 male pin strips
  • Micro-USB power connector
  • PCB Size: 86×56 mm. (Compatible with Raspberry Pi cases)

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Custom Zynq/CMOS Camera Unlocks Astrophotography

Around here we love technology for its own sake. But we have to admit, most people are interested in applications–what can the technology do? Those people often have the best projects. After all, there’s only so many blinking LED projects you can look at before you want something more.

[Landingfield] is interested in astrophotography. He was dismayed at the cost of commercial camera sensors suitable for work like this, so he decided he would create his own. Although he started thinking about it a few years ago, he started earnestly in early 2016.

The project uses a Nikon sensor and a Xilinx Zynq CPU/FPGA. The idea is the set up and control the CMOS sensor with the CPU side of the Zynq chip, then receive and process the data from the sensor using the FPGA side before dumping it into memory and letting the CPU take over again. The project stalled for a bit due to a bug in the vendor’s tools. The posts describe the problem which might be handy if you are doing something similar. There’s still work to go, but the device has taken images that should appear on the same blog soon.

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Amstrad on an FPGA

If you are from the United States and of a certain age, it is very likely you owned some form of Commodore computer. Outside the US, that same demographic was likely to own an Amstrad. The Z80-based computers were well known for game playing. [Freemac] implemented a working Amstrad CPC6128 using a Xilinx FPGA on a NEXYS2 demo board.

The wiki posting is a bit long, but it covers how to duplicate the feat, and also gives technical details about the design. It also outlines the development process used ranging from starting with a simple Z80 emulation and moving on to more sophisticated attempts. You can see a video of the device below.

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