How to make a heap profiler

Yossi Kreinin May 23, 2014

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...

Using the Beaglebone PRU to achieve realtime at low cost

Fabien Le Mentec April 25, 20148 comments

I work as an engineer in a synchrotron facility. A few weeks ago, I helped the people in charge of the power supply developments to integrate a realtime control algorithm on a prototype platform: a BeagleBone Black (BBB) running Linux. I had already worked with this board in the past, and I found it very interesting given its excellent resources versus price ratio (around 40 euros). This time, I was impressed by its realtime capabilities. I thought it would be a good idea to...

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...

Bad Hash Functions and Other Stories: Trapped in a Cage of Irresponsibility and Garden Rakes

Jason Sachs January 28, 20141 comment

I was recently using the publish() function in MATLAB to develop some documentation, and I ran into a problem caused by a bad hash function.

In a resource-limited embedded system, you aren't likely to run into hash functions. They have three major applications: cryptography, data integrity, and data structures. In all these cases, hash functions are used to take some type of data, and deterministically boil it down to a fixed-size "fingerprint" or "hash" of the original data, such that...

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: ...

Delayed printf for real-time logging

Yossi Kreinin October 25, 20133 comments

You often debug by adding a few printfs and looking at the logs. In some real-time/low-level contexts though, you don't have time for text formatting.

You don't want prints to affect timing too much, because then timing-related bugs you're chasing might disappear. And you certainly don't want the system to stop functioning altogether because prints cause it to miss real-time deadlines.

A common alternative to prints is more "raw" logging - an event buffer, where event is a union keeping...

Coroutines in one page of C

Yossi Kreinin August 20, 201315 comments

A coroutine is a function that you can jump back into after returning from it - and it remembers where it was in the code, and all the variables. This is very useful at times.

One use is generating a sequence of values. Here's how you can generate all the x,y pairs in a 2D range in Python:

def iterate(max_x, max_y): for x in range(max_x): for y in range(max_y): yield x,y for x,y in iterate(2,2): print x,y

This prints:

0 0 0 1 1 0 1 1

The yield keyword is like...

Code Metrics - SLOC Count

Stephen Friederichs August 19, 2013

Many programmers will start having flashbacks at the title of this article because it contains the words 'metrics' and 'SLOC'.  Newer programmers are probably wondering what all of the fuss is about - most probably have no negative connotations with the term 'code metrics' and some may not even know what SLOC is.  While there is much baggage associated with metrics and SLOC you shouldn't be afraid to gather fundamentally useful data such as SLOC count from your programming projects...

[ C Programming Techniques: integer type optimization ]

Fabien Le Mentec May 22, 20131 comment

I am currently working on a voltage controller running on a ATMEGA328P, ATMEL AVR 8 bits microcontroller. The controller logic is implemented in the main() routine and relies on a periodical timer whose frequency is fixed at application setup. Among other things, the timer ISR handler increments some per tick counters which are then used by the main routine to implement the voltage controller timing logic.By looking at the code, one noticed that I use the uint8_t type for counters instead of...

Watchdog Timer Anti-patterns

Alexandru Lazar June 8, 2019

The humble watchdog timer has been an essential part of our reliability tool chest for decades now. The way it works is straightforward and easy to understand, and most practical designs are easy to interface with.

There is a wealth of reference material that covers both the theory behind watchdog timers and practical design tips. But what we'll talk about today is of a slightly different nature.

Despite its straightforward operation and long history, the watchdog timer does occasionally get...

Coding Step 4 - Design

Stephen Friederichs November 24, 2015

Articles in this series:

The last article in this series discussed how to write functional high-level requirements: specifications for what your software is supposed to do. Software design is the other side of the coin....

Deeply embedded design example - Logic replacement

Gene Breniman July 9, 2011

I have always believed that some of the low-cost, low-pin count, low-resource microprocessors would make an excellent choice for the replacement of discrete logic components.  In these cases the deeply embedded microprocessor would become less of a general purpose computer and more of a logic replacement, providing a prescribed function with no connection to the outside world.  In a world of bigger, faster and more expensive, it is a pleasant change of pace...

Tenderfoot: Recommended Reading

Matthew Eshleman June 28, 20171 comment

Twenty years ago I read Code Complete by Steve McConnell. And then read it again. And again. And again. Of all the books I have read during my career, I believe this was the book that catapulted me from a young electrical engineer to a young and aspiring embedded software engineer. So to all the ‘tenderfoots’ embarking upon an embedded systems and especially embedded software and firmware career, this entry is for you.

First, I would certainly recommend that all engineers read and read...

C++ on microcontrollers 3 – a first shot at an hc595 class with 8 output pins

Wouter van Ooijen November 2, 2011

 previous parts: 1, 2

This blog series is about the use of C++ for modern microcontrollers. My plan is to show the gradual development of a basic I/O library. I will introduce the object-oriented C++ features that are used step by step, to provide a gentle yet practical introduction into C++ for C programmers.  Reader input is very much appreciated, you might even steer me in the direction you find most interesting.

In the first part of...

Embedded Toolbox: Windows GUI Prototyping Toolkit

Miro Samek July 7, 20172 comments

In this installment of my "Embedded Toolbox" series, I would like to interest you in the free Windows GUI Toolkit called QWin for prototyping, developing and debugging embedded C or C++ code on Windows.

If you work on devices with non-trivial user interfaces consisting of LCDs (segmented or graphic), buttons, LEDs, etc., QWin could be just the tool for you. It has improved my productivity in such projects dramatically. I personally consider it a gem in my "Embedded...

Introduction to Deep Insight Analysis for RTOS Based Applications

Jacob Beningo September 20, 20171 comment

Over the past several years, embedded systems have become extremely complex. As systems become more complex, they become harder and more time consuming to debug. It isn’t uncommon for development teams to spend more than 40% development cycle time just debugging their systems. This is where deep insight analysis has the potential to dramatically decrease costs and time to market.

Defining Deep Insight Analysis

Deep insight analysis is a set of tools and techniques that can be...

Surprising Linux Real Time Scheduler Behavior

Matthew Eshleman November 5, 2016

I have recently been helping with embedded software design and development for a data acquisition and visualization device. The software executes within an embedded Linux context and consists of various animated user interfaces rendering the acquired data.

The data is received via a UART and a SPI connection. During project development we noticed poor UART data latency issues during heavy user interface animations. For this product to properly meet its acquisition requirements, the UART...

Vala applications on Embedded Linux: maybe a clever choice [part 1]

Felipe Lavratti December 19, 2016

Vala is a sexy, open source, high level programming language that appeared in 2006, it counts with a modern typing system, is object oriented, compiled and statically typed, it has a almost identical syntax to C# and is maintained by GNOME. The language was created as a power abstraction of the GLib and GTK libraries, two considerably lightweight and powerful libraries written in C, and it is used in projects such as GNOME Clocks, Shotwell, GXml and Elementary OS.


Embedded Programming Video Course Teaches RTOS

Miro Samek January 20, 2019

If you'd like to understand how a Real-Time Operating System (RTOS) really works, here is a free video course for you:

RTOS part-1: In this first lesson on RTOS you will see how to extend the foreground/background architecture from the previous lesson, so that you can have multiple background loops running seemingly simultaneously.:

RTOS part-2: In this second lesson on RTOS you will see how to automate the context switch process. Specifically, in this lesson, you will start building...