## Summer of Gateware

September 18, 2015

This (last) summer the MyHDL project participated in the Google Summer of Code (GSoC) as a sub-organization under the Python Software Foundation (PSF). This was our first year participating - there was a lot for us to learn.  Overall it was a worthwhile and beneficial activity.

Being a first time sub-org we were limited to a maximum of two students.  We had nine students apply and twelve mentors volunteer.  Only being able to select two students...

In this article I will take a look at the wonderful MuPDF viewer and present a small modification that saves bookmarks alongside the pdf files, making it infinitely more useful.

Some days I sit down to work and wonder how anything ever gets done. A simple example.  When I work on an FPGA design, I wind up with 3 or 4 screens full of documentation, generally in PDF format.  There are the Xilinx manuals, the various tool manuals, language reference manuals, you name it.  While...

## Inside the Spartan-6: Using LUTs to optimize circuits

While building a small CPU on a Spartan-6 chip I came across the same old problem: my Verilog was mapping to a lot of slices . Way more then seems reasonable. So let's dig in and see what's really going on.

The J1 CPU (see Messing Around with a J1) is an amazingly streamlined design expressed in just over 100 lines of Verilog, and is reasonably compact at 150 Spartan-6 slices (half of that with the modifications described in the article).  But the Picoblaze is...

## Homebrew CPUs: Color Languages

June 17, 2015
Color Languages

Here on bizarro we program using -- get this – text!  Our other senses - hearing, touch, smell, are not used at all. Even our visual perception is greatly underutilized - we just use two-dimensional text on a flat display a foot in front of our eyes.

Color is just beginning to be used, although in a lame syntax coloring way only. Granted, it makes it easier to detect stupid syntax errors such as misspelled keywords. Sadly, color carries zero semantic or...

## Homebrew CPUs: Messing around with a J1

May 29, 2015

In this article I will examine James Bowman's excellent J1 CPU; I will then proceed to mess around with various parts of it, making it smaller, more appropriate to my particular application, and possibly faster.  I hope this will show you how easy it is to fiddle around with homemade CPUs and encourage you to make something weird and wonderful.

J1 CPU

My hat is off to James Bowman.  J1 is pretty cool.  It is a stack machine; it executes instructions in one cycle, it is...

## Makefiles for Xilinx Tools

Building a bitstream from an HDL is a complicated process that requires the cooperation of a lot of tools.  You can hide behind an IDE or grow a pair and use command line tools and a makefile to tie your build process together.  I am not a huge fan of makefiles either (I believe a language should be expressive enough to automate the build process), but the alternatives are dismal.

Command-line driven workflow is easier on the hands and faster.  The example...

## Use a Simple Microprogram Controller (MPC) to Speed Development of Complex Microprogrammed State Machines

Introduction

This article will describe a synthesizable HDL-based microprogram controller (MPC), or microprogram sequencer (MPS), that can be used to provide the control of a microprogrammed state machine. Unlike the microprogrammed state machines that I described in my previous two articles, "Use Microprogramming to Save Resources and Add Functionality" and "Fit Sixteen (or more) Asynchronous Serial Receivers in the Area of a Standard UART", many microprogrammed state machines will...

## Fit Sixteen (or more) Asynchronous Serial Receivers into the Area of a Standard UART Receiver

Introduction

This article will describe a technique, available in many current FPGA architectures, to fit a large amount of logic into a small area. About ten years ago now (Feb/Mar 2005), I helped develop a multi-line Caller ID product. The Multi-Channel Asynchronous Receiver (MCAR) FPGA core developed for that product will be used to illustrate the technique(s) needed to fit a 16 channel MCAR into a single Spartan II XC2S30-5VQ100 FPGA.

To stay true to the original design, I...

## Use Microprogramming to Save Resources and Increase Functionality

March 21, 2015
Introduction

Microprogramming is a design approach that every FPGA designer should have in their bag of tricks. I subscribe to the concept that microprogramming is a structured approach to the design of state machines. This is essentially the view of Maurice Wilkes when he first proposed microprogramming in 1951 as an alternative method for the implementation of the control section of a computer. Wilkes was interested in improving the reliability and reducing time needed to implement...

## I don’t often convert VHDL to Verilog but when I do ...

VHDL to Verilog

I don’t often convert VHDL to Verilog but when I do it is not the most exciting task in the world (that is an understatement).  For the most part I am HDL agnostic.  Well that is not true, I have a strong preference for MyHDL, and an insubstantial preference for VHDL over Verilog.  The choice of HDL for a project is often complicated, irrational, sometimes rational, but most often random.  It is often not a choice of the developer - for...

## Back from ESC Boston

NOT going to ESC Boston would have allowed me to stay home, in my comfort zone.

NOT going to ESC Boston would have saved me from driving in the absolutely horrible & stressful Boston traffic1.

NOT going to ESC Boston would have saved me from having to go through a full search & questioning session at the Canada Customs on my return2.

2017/06/06 update: Videos are now up!

So two days...

## Data Types for Control & DSP

There's a lot of information out there on what data types to use for digital signal processing, but there's also a lot of confusion, so the topic bears repeating.

I recently posted an entry on PID control. In that article I glossed over the data types used by showing "double" in all of my example code.  Numerically, this should work for most control problems, but it can be an extravagant use of processor resources.  There ought to be a better way to determine what precision you need...

## Welcoming MANY New Bloggers!

The response to the latest call for bloggers has been amazing and I am very grateful.

In this post I present to you the individuals who, so far (I am still receiving applications at an impressive rate and will update this page as more bloggers are added),  have been given access to the blogging interface.  I am very pleased with the positive response and I think the near future will see the publication of many great articles, given the quality of the...

## Sensors Expo - Trip Report & My Best Video Yet!

This was my first time at Sensors Expo and my second time in Silicon Valley and I must say I had a great time.

Before I share with you what I find to be, by far, my best 'highlights' video yet for a conference/trade show, let me try to entertain you with a few anecdotes from this trip.  If you are not interested by my stories or maybe don't have the extra minutes needed to read them, please feel free to skip to the end of this blog post to watch the...

## SEGGER's 25th Anniversary Video

Chances are you will find this video more interesting to watch if you take five minutes to first read the story of the week I spent at SEGGER's headquarters at the end of June.

The video is only a little more than 2 minutes long.  If you decide to watch it, make sure to go full screen and I would really love to read your thoughts about it in the comments down bellow.  Do you think a video like this succeeds in making the viewer want to learn more about the company?...

## Linear Feedback Shift Registers for the Uninitiated, Part II: libgf2 and Primitive Polynomials

July 17, 2017

Last time, we looked at the basics of LFSRs and finite fields formed by the quotient ring $GF(2)[x]/p(x)$.

LFSRs can be described by a list of binary coefficients, sometimes referred as the polynomial, since they correspond directly to the characteristic polynomial of the quotient ring.

Today we’re going to look at how to perform certain practical calculations in these finite fields. I maintain a Python library on bitbucket called...

## Fit Sixteen (or more) Asynchronous Serial Receivers into the Area of a Standard UART Receiver

Introduction

This article will describe a technique, available in many current FPGA architectures, to fit a large amount of logic into a small area. About ten years ago now (Feb/Mar 2005), I helped develop a multi-line Caller ID product. The Multi-Channel Asynchronous Receiver (MCAR) FPGA core developed for that product will be used to illustrate the technique(s) needed to fit a 16 channel MCAR into a single Spartan II XC2S30-5VQ100 FPGA.

To stay true to the original design, I...

## Feedback Controllers - Making Hardware with Firmware. Part 10. DSP/FPGAs Behaving Irrationally

November 22, 2018

This article will look at a design approach for feedback controllers featuring  low-latency "irrational" characteristics to enable the creation of physical components such as transmission lines. Some thought will also be given as to the capabilities of the currently utilized Intel Cyclone V, the new Cyclone 10 GX and the upcoming Xilinx Versal floating-point FPGAs/ACAPs.

Fig 1. Making a Transmission Line, with the Circuit Emulator

## binary hello world

Python + Ohio + MyHDL + FPGA

Recently I had the opportunity to coordinate a hands-on programmable hardware (FPGA) workshop (open-space) at a regional Python conference - @pyohio. The workshop was for those that had little to no exposure to programmable hardware. For this situation I used two basic examples: two versions of a binary hello world.

The binary hello world -- blinking an LED -- is a good starting point to introduce programmable hardware, hardware descriptions languages,...

## How precise is my measurement?

Some might argue that measurement is a blend of skepticism and faith. While time constraints might make you lean toward faith, some healthy engineering skepticism should bring you back to statistics. This article reviews some practical statistics that can help you satisfy one common question posed by skeptical engineers: “How precise is my measurement?” As we’ll see, by understanding how to answer it, you gain a degree of control over your measurement time.

An accurate, precise...