Playing around with FPGAs used to be a daunting prospect. You had to fork out a hundred bucks or so for a development kit, sign the Devil’s bargain to get your hands on a toolchain, and only then can you start learning. In the last few years, a number of forces have converged to bring the FPGA experience within the reach of even the cheapest and most principled open-source hacker.
[Ken Boak] and [Alan Wood] put together a no-nonsense FPGA board with the goal of getting the price under $30. They basically took a Lattice iCE40HX4K, an STMF103 ARM Cortex-M3 microcontroller, some SRAM, and put it all together on a single board.
The Lattice part is a natural choice because the IceStorm project created a full open-source toolchain for it. (Watch [Clifford Wolf]’s presentation). The ARM chip is there to load the bitstream into the FPGA on boot up, and also brings USB connectivity, ADC pins, and other peripherals into the mix. There’s enough RAM on board to get a lot done, and between the ARM and FPGA, there’s more GPIO pins than we can count.
Modeling an open processor core? Sure. High-speed digital signal capture? Why not. It even connects to a Raspberry Pi, so you could use the whole affair as a high-speed peripheral. With so much flexibility, there’s very little that you couldn’t do with this thing. The trick is going to be taming the beast. And that’s where you come in.
What would you get it you mashed up an FPGA and an Arduino? An FPGA development board with far too few output pins? Or a board in the form-factor of Arduino that’s impossible to program?
Fortunately, the ICEZUM Alhambra looks like it’s avoided these pitfalls, at least for the most part. It’s based on the Lattice iCE40 FPGA, which we’ve covered previously a number of times because of its cheap development boards and open-source development flow. Indeed, we were wondering what the BQ folks were up to when they were working on an easy-to-use GUI for the FPGA family. Now we know — it’s the support software for an FPGA “Arduino”.
The Alhambra board itself looks to be Arduino-compatible, with the horrible gap between the rows on the left-hand-side and all, so it will work with your existing shields. But they’ve also doubled them with pinheaders in a more hacker-friendly layout: SVG — signal, voltage, ground. This is great for attaching small, powered sensors using a three-wire cable like the one that you use for servos. (Hackaday.io has two Arduino clones using SVG pinouts: in SMT and DIP formats.)
The iCE40 FPGA has 144 pins, so you’re probably asking yourself where they all end up, and frankly, so are we. There are eight user LEDs on the board, plus the 28 I/O pins that end in pinheaders. That leaves around a hundred potential I/Os unaccounted-for. One of the main attractions of FPGAs in our book is the tremendous availability of fast I/Os. Still, it’s more I/O than you get on a plain-vanilla Arduino, so we’re not complaining too loudly. Sometimes simplicity is a virtue. Everything’s up on GitHub, but not yet ported to KiCad, so you can tweak the hardware if you’ve got a copy of Altium.
We’ve been seeing FPGA projects popping up all over, and with the open-source toolchains making them more accessible, we wonder if they will get mainstreamed; the lure of reconfigurable hardware is just so strong. Putting an FPGA into an Arduino-compatible form-factor and backing it with an open GUI is an interesting idea. This project is clearly in its very early stages, but we can’t wait to see how it shakes out. If anyone gets their hands on these boards, let us know, OK?
Thanks [RS] for the tip!
If you’ve ever worked with FPGAs, you’ve dealt with the massive IDEs provided by the vendors. Xilinx’s ISE takes about 6 gigabytes, and Altera’s Quartus clocks in at over 10 gigs. That’s a lot of downloading proprietary software just to make an LED blink.
[Jesús Arroyo]’s Icestudio is a new, graphical tool that lets you generate Verilog code from block diagrams and run it on the Lattice Semi iCEstick development board. A drag and drop interface lets you connect IOs, logic gates, dividers, and other elements. Once your block diagram is ready, a single button press downloads the code to the iCEstick.
Under the hood, Icestudio uses IceStorm, which we’ve discussed on HaD in the past, including this great talk by [Clifford], Icestorm’s lead. For the GUI, Icestudio uses nw.js, which spits out JSON based on the block diagram. This JSON is converted into a Verilog file and a PCF file. The Verilog is used to create the logic on the FPGA, and the PCF is used to define the pin configuration for the device. Clicking on selected modules reveals the generated Verilog if you want to know what’s actually going on.
It’s experimental, but this looks like a neat way to get started on FPGAs without learning a new language or downloading many gigs of toolchains. We’re hoping Icestudio continues to grow into a useful tool for education and FPGA development. A demo follows after the break.
[Thanks to Nils for the tip!]
Continue reading “Icestudio: An Open Source Graphical FPGA Tool”
Last time, I showed you a simple PWM block and an open source UART core. This time, I’ll put these parts together to create a PC PWM output peripheral.
Continue reading “PWM on the Lattice iCEStick”
I like to think that there are four different ways people use FPGAs:
- Use the FPGA as a CPU which allows you to add predefined I/O blocks
- Build custom peripherals for an external CPU from predefined I/O blocks
- Build custom logic circuitry from scratch
- Projects that don’t need an FPGA, but help you learn
I’d bet the majority of FPGA use falls into categories one and two. Some FPGAs even have CPUs already built-in. Even without an onboard CPU, you can usually put a CPU “core” (think reusable library) into the chip. Either way, you can always add other cores to create UARTs, USB, Ethernet, PWM, or whatever other I/O you happen to need. You either connect them to a CPU on the chip, or an external one. With today’s tools, you often pick what you want from a list and then your entire project becomes a software development effort.
Continue reading “Taking the Pulse (Width Modulation) of an FPGA”
FPGA development has advanced dramatically in the last year, and this is entirely due to an open-source toolchain for Lattice’s iCE40 FPGA. Last spring, the bitstream for this FPGA was reverse engineered and a toolchain made available for anything that can run Linux, including a Raspberry Pi. [Dave] from Xess thought it was high time for a Raspberry Pi FPGA board. With the help of this open-source toolchain, he can program this FPGA board right on the Raspberry Pi.
The inspiration for [Dave]’s board came from the XuLA and StickIt! boards that give the Raspberry Pi an FPGA hat. These boards had a problem; the Xilinx bitstreams had to be compiled on a ‘real’ PC and brought over to the Raspberry Pi world. The new project – the CAT Board – brings an entire FPGA dev kit over to the Raspberry Pi.
The hardware for the CAT Board is a Lattice iCE-HX8K, 32 MBytes of SDRAM, a serial configuration flash, LEDs, buttons, DIP switches, grove connectors, and SATA connectors (although [Dave] is just using these for differential signals; he doesn’t know if he can get SATA hard drives to work with this board).
Despite some problems with his board house, [Dave] eventually got his FPGA working, or at least the bitstream configuration part, and he can blink a pair of LEDs with a Raspberry Pi and programmable logic. The Hello World for this project is done, and now the only limit is how many gates are on this FPGA.
Continue reading “FPGAs For The Raspberry Pi”
FPGAs are great, but open source they are not. All the players in FPGA land have their own proprietary tools for creating bitstream files, and synthesizing the HDL of your choice for any FPGA usually means agreeing to terms and conditions that nobody reads.
After months of work, and based on the previous work of [Clifford Wolf] and [Mathias Lasser], [Cotton Seed] has released a fully open source Verilog to bitstream development tool chain for the Lattice iCE40LP with support for more devices in the works.
Last March, we saw the reverse engineering of the Lattice ICE40 bitstream, but this is a far cry from a robust, mature development platform. Along with Yosys, also written by [Clifford Wolf] it’s relatively simple to go from Verilog to an FPGA that runs your own code.
Video demo below, and there’s a ton of documentation over on the Project IceStorm project page. You can pick up the relevant dev board for about $22 as well.
Continue reading “An Open Source Toolchain For iCE40 FPGAs”