Embedded Muse 135 Copyright 2006 TGG October 24, 2006

EDITOR: Jack Ganssle, jack@ganssle.com

CONTENTS:
- Editor’s Notes
- New kinds of Debugging Tools
- More on Reading Code
- Start With the Manual
- Tools
- Jobs!
- Joke for the Week
- About The Embedded Muse

Editor’s Notes

Do you have a dozen or more developers who could benefit from this firmware training? I can present my Better Firmware Faster class at your facility. See https://www.ganssle.com/classes.htm .

For European readers, I’ll be giving a couple of talks at Oredev in Malmo, Sweden in November. This new conference looks interesting, with some intriguing speakers like Betrand Meyer and Martin Fowler. More info here: http://www.oredev.org/ .

Paul Swingle wrote about another source of free books. I haven’t tried this yet but it sounds interesting: Your citation of a source of free online books reminded me of a tremendous site: www.NetLibrary.com. They have books online for free. Amazingly you can search the whole library by the content of the books. For example you could look for all books containing "embedded and design and firmware" and it would respond with the 83 books that contain all three of those words. The books contain in the physical books including the cover, table of contents, figures, photographs, and index.

The catch is that you must sign up initially in a library that offers the service. In my experience, most public libraries and almost all university libraries offer it (although they often don't know they do). The bigger libraries seem to have bigger collections ( I presume that the more they pay, the more titles they can offer). You do not have to belong to the library; you can just walk in and sign on using one of their computers. After you have signed up, you can use the service anytime, anywhere.

In response to my links to some approximations, Bernd Toerner sent this: You have mentioned approximations routines for trigonometry functions. Perhaps it is interesting for the readers that there is an other way to calculate the functions: CORDIC. Basically it is a way to do this job in hardware with FPGA, but on uC it is possible too (need no variables of float or double type, only integers; the calculation is done with simple addition and shift operations)

You can find information at http://www.dspguru.com/info/faqs/cordic.htm and http://www.andraka.com/cordic.htm

New Kinds of Debugging Tools

We know a lot about getting rid of bugs. One approach is to use tools (like Ada or SPARK) that keep us from making mistakes in the first place. Another is to employ inspections to remove bugs before we start debugging. Test finds those that slip through.

Then there’s static analysis, which finds defects before code inspection. Lint, for instance, has been around for ages and has become widely adopted. But in recent years new classes of static analyzers, those that find runtime errors without executing the code, have been clamoring for attention. Companies like Polyspace, Klocwork, Coverity and others offer these sorts of compelling products.

I find this sort of technology fascinating. Pour your source code through a tool which identifies the bugs? Cool! You’d think the companies would be beating customers away. Price would be immaterial.

But do the tools actually work?

If you’re using, or have used, these advanced static analyzers, drop me an email. Were you happy with the tools? Were they worth the price? Why or why not? What sorts of errors were trapped… and which slipped through?

I’ll share the results in a future Muse.

More on Reading Code

For a number of years now, I've been involved in the Linux and Open Source movements primarily teaching Linux to embedded developers.
But, frankly, I'm absolutely appalled at the quality of Open Source source code. Sadly, the vast majority of it is write-only. Someone obviously wrote it, but no one else can read it.

I have seen many open source code files where the ^only^ comment is the GPL boilerplate at the top. And it's not like the code itself offers any useful hints. All too many programmers seem to have an aversion to vowels in symbol names.

For a long time, I have advocated the view that programming really has very little, if anything, to do with computers. The computer doesn't understand C, it doesn't even understand assembly language.
Heck, even the 1's and 0's are abstractions.

When you write a program, what you're really doing is communicating to another human what it is you want the computer to do. Programming is about communication, just like any other form of writing. So yes, computer science students should be exposed to good writing. But since there's so precious little of it in computer science, maybe they just need some basic creative writing classes.

Several readers wondered if there was a good place to find truly beautiful C++ source to read. I’m stumped. Any ideas?

I started the development, and when I finished the first prototype, I installed it in the car, so he could test it. He tested the product for two days, and then came with new features to put in the firmware, always asking "is it possible to implement such a function", and I said "yes, of course" and that answer always made him happy.

Then, I put the new firmware in his prototype. He tested for a day or two, and then came back with new ideas. I told him some "yes, it’s possible" and I wrote new functions for the product. The third time he asked for new functions, I asked him if the product would not become too complicated for the user, but he said no. Well, my job was to write the firmware, so I did it. He asked me some more functions, and I wrote all of them. When the product was quite stable, he started the first production.

Out of curiosity, I picked up the user’s manual he wrote, and took a look. He wrote about only 1/3 of features of the product. I asked him why he did so, and the answer was funny: because it would be too complicated for the user. Well, what happened was not so funny: some users called me with questions about problems with the product, that was in fact features, but the manual didn’t say about that. And as a result, a lot of functions became ignored in the manual, and consequently by the user, functions that I had to write, debug, document, etc.

The next product he asked me to make, I said to him to imagine all the product functions, and to first of all write the users manual. To develop that product was a heaven: when I made a product that did all of the manual functions, the product was finished. Today, I think is a really good approach for any product development.

Tools

Roland Bennett likes PSPad: I really appreciate the feedback from users regarding their favorite editors. Having used Visual SlickEdit for many years, I was looking for a free editor when I left the company where I had used it.

I used Notepad++ for a long time, and appreciated the fact that I could add the keywords for VxWorks to the code completion function by simply copy and pasting the text from the VxWorks PDF manuals into a text file!

However recently I discovered an even better editor: PSPad. http://www.pspad.com/en/ ,which has all the options I wish Notepad++ had! Difference tool, hex editor, file explorer, etc.

Jobs!

Joke for the Week

Now here's where it REALLY takes off...

10**2 bits: a hectobit (100 bits)
- For example, the key size for some encryption algorithms these days

10**3 bits: a kilobit (1,000 bits)
- For example, the size of the magnetic stripe on your credit card
- 1/75 of a second of one channel of audio

10**4 bits: (10,000 bits)
- one page of typewritten text

10**5 bits: the size of a short-to-medium newspaper article

10**6 bits: a megabit
- a one-page black and white fax
- one frame of a DVD (about 1/30 of a second)

10**7 bits:
- the size of a screenfull of data on a medium-resolution monitor
- a single 3.5" floppy disk (remember those?)

10**8 bits:
- amount of data in a large foldout map
- amount of data in a 5-minute, CD-quality recording
- amount of data your eyes can digest in a single glance

10**9 bits: a gigabit
- the capacity of a regular audio CD

1o**10 bits: the capacity of a single-sided DVD

10**11 bits: the capacity of a Blu-ray (high-def) DVD

10**12 bits: a terabit
- A medium sized hard drive these days
- the amount of space needed to store the largest number of digits of pi ever recorded (1.24 trillion)

10**13 bits: possibly the capacity of your functional memory

10**14 bits: the size of the Library of Congress in digital form

10**15 bits: a petabit
- The size of the Internet Archive (an organization that tries to maintain an archive of the Internet)

10**16 bits: the amount of hard drive space that Google uses

10**17 bits: the size of the memory of the robot, Data, in Star Trek: 800,000,000,000,000,000 bits

10**18 bits: an exabit
- The amount of all printed material in the world

Putting it all in perspective...

10**22 bits: the amount of data stored in 1 gram of your DNA.

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