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Introduction to Microcontrollers - 7-segment displays & Multiplexing

Mike Silva August 14, 20141 comment

Doing the 7 Segment Shuffle

The 7 segment display is ubiquitous in the modern world.  Just about every digital clock, calculator and movie bomb has one.  The treadmills at my gym have 6 or 7, each one displaying 3 or 4 digits.  What makes the 7-seg interesting is that it presents an opportunity to make a trade off between GPIO (output pins) for time.  Every 7-seg display requires 8 outputs (the 7 segments and usually either a decimal point or a...


How to make a heap profiler

Yossi Kreinin May 23, 20141 comment

We'll see how to make a heap profiler. Example code for this post makes up heapprof, a working 250-line heap profiler for programs using malloc/free.

It works out of the box on Linux (tested on "real" programs like gdb and python). The main point though is being easy to port and modify to suit your needs. The code, build and test scripts are at github.

Why roll your own heap profiler?

  • It's easy! And fun, if you're that sort of person. What, not reasons enough? OK, how...

Lost Secrets of the H-Bridge, Part IV: DC Link Decoupling and Why Electrolytic Capacitors Are Not Enough

Jason Sachs April 29, 20147 comments

Those of you who read my earlier articles about H-bridges, and followed them closely, have noticed there's some unfinished business. Well, here it is. Just so you know, I've been nervous about writing the fourth (and hopefully final) part of this series for a while. Fourth installments after a hiatus can bring bad vibes. I mean, look what it did to George Lucas: now we have Star Wars Episode I: The Phantom Menace and


Unit Tests for Embedded Code

Stephen Friederichs March 5, 201411 comments

I originate from an electrical engineering background and my first industry experience was in a large, staid defense contractor. Both of these experiences contributed to a significant lack of knowledge with regards to software development best practices. Electrical engineers often have a backwards view of software in general; large defense contractors have similar views of software and couple it with a general disdain for any sort of automation or ‘immature’ practices.  While there...


Implementing State Machines

Stephen Friederichs January 18, 20145 comments

State machines are a great way to design software but they can be difficult to implement well.To illustrate this I’ll develop a simple state machine then increase the complexity to demonstrate some of the difficulties

We’ve all washed dishes before - it’s easy isn’t it? Scrub, rinse, dry, scrub, rinse dry. Scrub the dish until all of the gunk is off of it, rinse until the soap is off, put it in the drying rack. If you want to design software to implement this you have options. You...


Understanding and Preventing Overflow (I Had Too Much to Add Last Night)

Jason Sachs December 4, 2013

Happy Thanksgiving! Maybe the memory of eating too much turkey is fresh in your mind. If so, this would be a good time to talk about overflow.

In the world of floating-point arithmetic, overflow is possible but not particularly common. You can get it when numbers become too large; IEEE double-precision floating-point numbers support a range of just under 21024, and if you go beyond that you have problems:

for k in [10, 100, 1000, 1020, 1023, 1023.9, 1023.9999, 1024]: try: ...

How to Arduino - a video toolbox

Lonnie Honeycutt November 15, 20131 comment

I've begun producing a new series of video tutorials for the hobbyist new to the Arduino or microcontrollers in general.  My videos are very pragmatic - I prefer to answer the question "what is the quickest, simplest and most affordable way to accomplish this?".  The videos are meant to be a quick source of "how to" knowledge for the hobbyist that is using an LCD display, ultrasonic sensor or accelerometer for the first time, for example.  I hope you enjoy this series of...


Introduction to Microcontrollers - Driving WS2812 RGB LEDs

Mike Silva November 14, 201330 comments

This tutorial chapter is a bit of a detour, but I think an interesting and useful one.  It introduces a bit of assembly language programming, and demonstrates bit-banging a tight serial data protocol.  And it deals with RGB LEDs, which are just very fun in their own right, especially these new parts.  So I thought I'd post this to give readers time for some holiday lighting experimenting.

Back To The Future

Remember how we started this...


Introduction to Microcontrollers - Button Matrix & Auto Repeating

Mike Silva November 12, 2013

Too Many Buttons, Not Enough Inputs

Assigning one GPIO input to each button can use up a lot of GPIO pins.  Numeric input requires at least 10 buttons, plus however many additional control or function buttons.  This can quickly get expensive, GPIO pin-wise, and also connector-wise if the keypad is off the uC PCB as it often would be.  A very common response to this expense is to wire buttons (keys, etc) in a matrix.  By connecting our buttons in an...


Energia - program a TI MSP430 using Arduino sketches

Lonnie Honeycutt November 5, 20131 comment
TI MSP430 Launchpad

I started tinkering with microcontroller a couple of years ago with an Arduino Uno.  I had a little experience with C, so programming in the Arduino environment has been relatively easy and straightforward for me.  My code is not necessarily elegant or efficient, but I can usually figure out how to make an Arduino do what I want it to do eventually.  A lot of credit to the Arduino userbase, as it is very easy to figure most things out with a quick Google...


Which MOSFET topology?

Jason Sachs September 1, 20119 comments

A recent electronics.StackExchange question brings up a good topic for discussion. Let's say you have a power supply and a 2-wire load you want to be able to switch on and off from the power supply using a MOSFET. How do you choose which circuit topology to choose? You basically have four options, shown below:

From left to right, these are:

High-side switch, N-channel MOSFET High-side switch, P-channel MOSFET Low-side switch, N-channel...

Introduction to Microcontrollers - 7-segment displays & Multiplexing

Mike Silva August 14, 20141 comment

Doing the 7 Segment Shuffle

The 7 segment display is ubiquitous in the modern world.  Just about every digital clock, calculator and movie bomb has one.  The treadmills at my gym have 6 or 7, each one displaying 3 or 4 digits.  What makes the 7-seg interesting is that it presents an opportunity to make a trade off between GPIO (output pins) for time.  Every 7-seg display requires 8 outputs (the 7 segments and usually either a decimal point or a...


Cortex-M Exception Handling (Part 1)

Ivan Cibrario Bertolotti November 28, 20152 comments

This article describes how Cortex-M processors handle interrupts and, more generally, exceptions, a concept that plays a central role in the design and implementation of most embedded systems.


Introduction to Microcontrollers - More On Interrupts

Mike Silva September 25, 2013

A Little More Detail About The Interrupt Mechanism

It's time to look a little closer at what happens in an interrupt request and response.  Again this is in general terms, and different microcontroller designs may do things somewhat differently, but the basics remain the same.  Most but not all interrupt requests are latched, which means the interrupt event sets a flag that stays set even if the interrupt event then goes away.  It is this latched flag...


VHDL tutorial - A practical example - part 1 - Hardware

Gene Breniman May 18, 20111 comment

In previous posts I described some simple VHDL examples.  This time let's try something a little more complex. This is part one of a multiple part article.  This is intended to be a detailed description of one of several initial designs that I developed for a client.  This design never made it into a product, but a similar design was used and is currently being produced.  As a considerable amount of work was put into this effort, I decided to share this design...


Arduino robotics #4 - HC-SR04 ultrasonic sensor

Lonnie Honeycutt October 20, 20131 comment
Arduino Robotics

Arduino robotics is a series of article chronicling my first autonomous robot build, Clusterbot.  This build is meant to be affordable, relatively easy and instructive.  The total cost of the build is around $50.  

1. Arduino robotics - motor control2. Arduino robotics - chassis, locomotion and power3. Arduino robotics - wiring, coding and a test run4.

Coding Step 1 - Hello World and Makefiles

Stephen Friederichs February 10, 20156 comments

Articles in this series:

Step 0 discussed how to install GCC and the make utility with the expectation of writing and compiling your first C program. In this article, I discuss how to use those tools we installed last time. Specifically, how to use GCC to compile a C program and...


C Programming Techniques: Function Call Inlining

Fabien Le Mentec April 29, 20137 comments
Introduction

Abstraction is a key to manage software systems as they increase in size and complexity. As shown in a previous post, abstraction requires a developper to clearly define a software interface for both data and functions, and eventually hide the underlying implementation.When using the C language, the interface is often exposed in a header '.h' file, while the implementation is put in one or more  corresponding '.c' files.

First, separating an interface from its...


Cortex-M Exception Handling (Part 2)

Ivan Cibrario Bertolotti February 1, 20169 comments

The first part of this article described the conditions for an exception request to be accepted by a Cortex-M processor, mainly concerning the relationship of its priority with respect to the current execution priority. This part will describe instead what happens after an exception request is accepted and becomes active.

PROCESSOR OPERATION AND PRIVILEGE MODE

Before discussing in detail the sequence of actions that occurs within the processor after an exception request...


VHDL tutorial - combining clocked and sequential logic

Gene Breniman March 3, 2008

In an earlier article on VHDL programming ("VHDL tutorial" and "VHDL tutorial - part 2 - Testbench", I described a design for providing a programmable clock divider for a ADC sequencer. In this example, I showed how to generate a clock signal (ADCClk), that was to be programmable over a series of fixed rates (20MHz, 10MHz, 4MHz, 2MHz, 1MHz and 400KHz), given a master clock rate of 40MHz. A reader of that article had written to ask if it was possible to extend the design to...