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Writing good code is hard. Testing it is arguably even harder. And with the advance of modern technologies, the demand for good verification only keeps growing along with it. However, especially the FPGA world appears to commonly use obsolete and inappropriate verification tools and methodologies. But it doesn’t have to be this way! This post outlines, guided by a real-world example, how to use modern verification languages and tools to create high-quality test benches in less time.
-- Now that's my definition of building a computer!
Figure 1. The finished LW-35
Do you still remember the old electronic typewriters from the nineties? Many of the later machines were already pretty much full-fledged computers, just with a word processor as the operating system. One of these typewriters is the Brother LW-35 released in Europe. I still had one of these lying around; Great keyboard, a fun daisy wheel printer, and a 14 line display for distraction free writing. It even had a floppy drive for data exchange. So in summary, a pretty cool device.
But there were a few problems with it. First of all, the floppy drive stopped working reliably. And secondly, on the days the floppy drive decided to work, it was still a floppy drive. Not exactly the most convenient way to store and transfer data these days, although I'm sure some of you will disagree. Also, the typewriter used its own file format, which needed to be converted on the device itself before it could be read in a DOS or UNIX environment. This may be OK if you're writing a longer document, and only write it on that machine. But as someone who constantly changes the machine they type on, it's not practical.
Yet, even with these problems, I just didn't have the heart to throw it out.
So what can we do about it? Upgrade it!
In this post, I will show you how I converted my old LW-35 typewriter into a modern computer while keeping all the good features of the old machine.
-- Building an FPGA from 74-series logic ICs. For fun and education.
Figure 1. TTL-FPGA
Technology is becoming more complex every day. Devices get smaller, integration gets higher. Consequently, it is becoming increasingly harder to understand how modern devices work.
In the 80s, you could open your PC and start probing signals on the mainboard to understand which instruction the CPU executed. These days, pretty much everything can be integrated into a single chip and everything is hidden away. One example of such a highly integrated component is the field programmable gate array (FPGA).
FPGAs essentially allow the designer to create large digital designs inside of an IC without having to create actual new silicon. As these designs are created by writing software-like source code, one might easily forget the fact that what is created is, indeed, a digital circuit. The immense overhead to provide this flexibility is easy to underestimate when working with these devices.
To aid students learning about FPGAs better understand the technology, this project aims to provide a platform to look at the inner workings of such a chip by breaking it out of the IC and bringing it onto a PCB where every signal can be traced and measured. Such projects are often done for central processing units (CPUs), but there isn't much when it comes to FPGAs.
Before I delve any deeper into my implementation, I want to highlight that this is only one of many ways to construct such an "FPGA." Also, this project does not accurately represent the circuits inside a commercial FPGA. Many things, especially the routing, had to be grossly simplified in order to be feasible. The basic concepts, however, should still hold true.
Figure 1. Thank you for 2018! 2018 is coming to an end, and so it's time to tend to things that didn't get done over the year.
For me, I've been wanting to talk about many of my old projects for quite a while now, but never got around to it.
So this December (or tbh, many were shot during November), I pulled together and made videos for 25 of my projects. They date from very recent (November 2018) back to my school days (2007), so there's quite some variation to the style and type of project. I hope that you will enjoy (at least some of) them.
Markus | Updated Monday, November 27th 2017, 18:37
-- Tiny and cheap, but versatile
Figure 1. A rendered 3D-image of the Tiny-XO2 board
Introduction
The Tiny-XO2 is a small, versatile and cost-effective development platform for Lattice MachXO2 field-programmable gate arrays (FPGAs). It is built around a MachXO2-1200HC FPGA which features 1280 LUTs, 64 kbits of EBR SRAM and one PLL besides various other features[1]. The development board extends the functionality by providing a USB-to-serial converter and a crystal to allow quick and easy prototyping. All I/O pins are available on the .1 inch headers and labelled directly on the board. Figure 2 provides an overview of all the board's functions.
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This video demonstrates a little program I wrote to emulate vcom/vsim using GHDL. It enables Sigasi to check syntax and to simulate using GHDL/GtkWave.
