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

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

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

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

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

November 5, 20131 comment

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...

## Introduction to Microcontrollers - Buttons and Bouncing

What Is A Button?

To your hardware, that is.  As discussed in Introduction to Microcontrollers - More On GPIO, a button (or key, or switch, or any form of mechanical contact) is generally hooked up to a microcontroller so as to generate a certain logic level when pushed or closed or "active," and the opposite logic level when unpushed or open or "inactive."  The active logic level can be either '0' or '1', but for reasons both historical and electrical, an...

## Arduino robotics #4 - HC-SR04 ultrasonic sensor

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. ## Arduino robotics #3 - wiring, coding and a test run October 17, 2013 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.

October 16, 2013
Arduino Robotics

Beginner 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. ## Introduction to Microcontrollers - More Timers and Displays October 15, 20131 comment Building Your World Around Timers By now you have seen four different ways to use timers in your programs. Next we will look at some ways to produce the effect of multiple parallel streams of work in your program with the help of timers. This effect is only an appearance, not a reality, since a single microcontroller (one core) can only run a single thread of code. However, since microcontrollers are so fast in relation to a great many of the tasks to... ## Introduction to Microcontrollers - Timers September 27, 20132 comments Timers - Because "When" Matters Computer programs are odd things, for one reason because they have no concept of time. They may have the concept of sequential execution, but the time between instructions can be essentially any number and the program won't notice or care (unless assumptions about time have been built into the program by the programmer). But the real world is not like this. In the real world, especially the real embedded world,... ## Introduction to Microcontrollers - More On GPIO September 13, 20134 comments Now that we have our LED Blinky program nailed down, it's time to look more closely at outputs, add button/switch inputs, and work with reading inputs and driving outputs based on those inputs. It's ON - No, It's OFF - No, It's ON... I have to confess, I cheated. Well, let's say I glossed over something very important. In our LED Blinky program, we never cared about whether an output '1' or an output '0' turned on the LED. Since we were just... ## Endianness and Serial Communication May 20, 2013 Endianness is a consideration that is easily overlooked in the design of embedded systems. I myself am amply guilty of this oversight. It’s something you don’t ever have to worry about if you’re only working with a single processor or two processors that have the same endianness. You can even avoid it if you have two processors that have different endianness but never transmit data between themselves that consists of more than one byte. It’s easy to lull... ## Unit Tests for Embedded Code 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... ## Introduction to Microcontrollers - Buttons and Bouncing October 26, 20133 comments What Is A Button? To your hardware, that is. As discussed in Introduction to Microcontrollers - More On GPIO, a button (or key, or switch, or any form of mechanical contact) is generally hooked up to a microcontroller so as to generate a certain logic level when pushed or closed or "active," and the opposite logic level when unpushed or open or "inactive." The active logic level can be either '0' or '1', but for reasons both historical and electrical, an... ## Arduino robotics #4 - HC-SR04 ultrasonic sensor 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.

## Which MOSFET topology?

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...

## Implementing State Machines

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...

## How to Build a Fixed-Point PI Controller That Just Works: Part II

In Part I we talked about some of the issues around discrete-time proportional-integral (PI) controllers:

• various forms and whether to use the canonical form for z-transforms (don't do it!)
• order of operation in the integral term: whether to scale and then integrate (my recommendation), or integrate and then scale.
• saturation and anti-windup

In this part we'll talk about the issues surrounding fixed-point implementations of PI controllers. First let's recap the conceptual structure...