Efficient C Tip #13; Automotive Safety

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Firmware Update

- December 17, 2013

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in this issue

-- Toyota's Electronic Throttle Control Software

-- Spring 2013 Hands-on Embedded Skills Training

-- Efficient C Tip #13: Use Mod (%) with Caution

-- Industry News That's Not Boring

Firmware Update is a free newsletter by embedded guru Michael Barr. This issue is Copyright 2013 by Barr Group, but may be reprinted for non-commercial purposes. Please forward it to colleagues who may benefit from the information.

Toyota's Electronic Throttle Control Software

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Some of you have asked me about the recent headlines regarding software issues and unintended automobile acceleration and my October courtroom testimony regarding Toyota's engine software. I am limited in what I can say publicly about this, but here are some links for those of you that are interested:

The Single Bit Flip that Killed (EE Times)
Killer Firmware: Bad Design and Its Consequences (EDN)
Vehicle Testing Confirms Fatal Flaws (EE Times)
No Pedal Misapplication in Toyota Case (Design News)
Inside Camry's Engine Control Module (EE Times)

Obviously, we all would benefit from attention-to-detail in safety-critical software design.

Read the courtroom testimony...

Spring 2013 Hands-on Embedded Skills Training

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As you plan your Spring work schedule, take note that Barr Group will present three week-long training courses to upgrade the skills of embedded systems engineers. Each consists of a series of detailed lectures and challenging but fun hands-on programming exercises.

Embedded Software Boot Camp in Palo Alto starting Apr 28
Embedded Android Boot Camp in Maryland starting May 5
Embedded Security Boot Camp in Palo Alto starting May 19

Register early to save your seat and take advantage of the early registration discount. Keep in mind also that December is a great time to put excess current-year training funds to use.

Read the full details...

Efficient C Tip #13: Use Mod (%) with Caution

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If you want to write efficient C, you need to be cautious about using the modulus operator (%). This is because "a % b" is equivalent to "a - b * (a / b)". In plain English, a single mod involves three arithmetic operations. Thus C code that achieves the desired end calculation without using mod is more efficient C code.

Read about the alternatives...

Industry News That's Not Boring

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Apple engineer recreates 2,100 y.old Greek "computer" to forecast future eclipse dates entirely out of Lego parts. http://www.fastcodesign.com/1662831/watch-an-apple-engineer-recreate-a-2000-year-old-computer-using-legos

12 interesting facts about linkers and ELF object files: http://j.mp/1e6zmzd

Software development advice from Robert Frost: "Don't ever take a fence down until you know why it was put up."

A tutorial on the implementation of dynamic memory allocation on the heap in C, including malloc(). http://www.inf.udec.cl/~leo/Malloc_tutorial.pdf

If carpenters were hired like programmers: "Must have at least 5 yrs experience with the Dewalt 18V 165mm Circular Saw"

Tiny Shell (tinysh) open source command line shell facilities (e.g., over UART). http://tinysh.sourceforge.net

100,000,000,000,000,000,000 is the approximate number of transistors in the world.
10,000,000,000,000,000 is the approximate number of ants.

Code Reviews: Funny (comic) but too easily true... http://www.bonkersworld.net/code-reviews/

Description of how LCDs work with more construction details than are usually provided. http://www.youtube.com/watch?v=d4QFNWBSZYg

Learn about cryptography by solving coding problems derived from weaknesses in real-world systems. http://www.matasano.com/articles/crypto-challenges/