Embedded Muse 142 Copyright 2007 TGG March 5, 2007

EDITOR: Jack Ganssle, jack@ganssle.com

CONTENTS:
- Editor’s Notes
- An ESL Survey
- English as a First Language
- Last Buy
- Tools & Tips
- Book Review
- Jobs!
- Joke for the Week
- About The Embedded Muse

Editor’s Notes

Or, come to Boston May 4, where I’ll present this class at the Sheraton Braintree hotel. Registration and other info here: https://www.ganssle.com/classes.htm . You’ll earn 0.7 Continuing Education Units, learn a lot, and hopefully have a bit of fun, too.

The Embedded Systems Conference is coming to San Jose April 1-5. It’ll be a whirlwind. I’m giving 5 talks, and am really looking forward to the teardown of a Toyota Prius, which couldn’t exist without an awful lot of embedded smarts. The currently super-controversial Al Gore is giving the keynote, a very interesting move on the part of conference management, considering how conservative engineers are. But no one will complain about Orange County Choppers being there… though what they have to do with embedded is beyond me. Fun? You betcha. If you come to the conference do stop me and say hello.

I’ve created a video titled “Develop Firmware in Half the Time” that distills the basic ideas and processes needed to efficiently crank out great firmware. There’s more information available at https://www.ganssle.com/video.htm .

Ralf Holly commented on my reference to an article: “Regarding Dan Saks compile-time assertions article. I wrote an article about compile-time assertions for C/C++ User's Journal; it shows different implementations and various examples on how and when to use them. It is available online at http://www.ddj.com/dept/cpp/184401873?pgno=1 .” Worth reading.

I’m trying to tune an application that preprocesses C programs to extract contracts (a la Bertrand Meyer’s Design by Contract ™). But it’s written in Ruby and racc. If anyone knows those programs and is willing to give a couple of hours of thought, please contact me. No fortune, not much fame, but it might be fun.

An ESL Survey

VDC, an independent technology research firm, is conducting research on the market for ESL (Electronic System Level) tools market. The research covers embedded hardware, system, and software design and VDC is looking for help from developers with recent experience in engineering embedded systems.

In appreciation of your participation, VDC will provide all respondents who complete the survey a summary of the research findings and also enter these respondents into a drawing for one of three (3) $100 Amazon.com gift certificates (drawing to be held April 25th, 2007).
To participate, please visit:
www.vdc-corp.com/esl?PID=GA

English as a First Language

In fact many colleges now recognize the mixed skills needed in our industry with the Computer Engineering degree program, a sort of watered down EE with serious software emphasis. It takes a lot more code than hardware to build an embedded system, so a software focus just makes sense. Most surveys peg firmware at 70-80% of a product’s development effort.

When hiring firmware developers I’ve found little difference between each of these majors as long as the candidates have practical experience. In some particular industries, though, which degree might be important. One company I know almost exclusively hires mechanical engineers. They, too, get quite a bit of programming experience in college. Their sound understanding of machine control is what’s important to this company that makes material handling equipment.

ME, EE, CS, CE – all are engineering or engineering-like programs that stress practical problem-solving abilities. We’re taught to build things, to decompose big problems into solvable chunks. That in a large sense differentiates us from our friends studying the liberal arts.

Donald Knuth promoted the idea of Literate Programming, an approach that intermixed code and description, the description being expressed using TeX, a graphical word-processor-like formatting scheme. Postprocessors separated the description from the code. But central to his idea was that of very carefully expressing one’s intentions, using all the richness of the English language instead of the abbreviated cryptic comments so typical in most code.

I’ve found that some of the best developers of all are English majors. They’ll often graduate with no programming experience at all, and certainly without a clue about the difference between DRAM and EPROM.

But they can write. That’s the art of conveying information concisely and clearly. Software development and writing are both the art of knowing what you’re going to do, and then lucidly expressing your ideas.

The worst developers, regardless of background, fail due to their inability to be clear. Their thoughts and code tend to ramble rather than zero-in on the goal.

Too many engineering-trained developers have a total disregard for stylistic issues in programming. Anything goes. Firmware is the most expensive thing in the universe, so it makes sense to craft it carefully and in accordance with a standard style guide. Make sure it clearly communicates its intent. This is where the English majors shine; they’ve spent 4 years learning everything there is to know about styles and communication.

In fact, the best programming book ever written was first published in 1914 and never mentions computers. It’s “The Elements of Style”, by William Strunk and E. B. White (Allyn & Bacon; ISBN: 020530902X). It’s a slender volume of 105 pages that tells us how to write well. Just five bucks from Amazon.com. My observation is that most programmers are in dire need of such help. Unless a program’s comments are in well-formed English that unambiguously express the developer’s intent, the code is junk. Just as we’ve got to conform to C’s syntax to make a useful routine, our comments must be in solid English to aid future maintenance. And maintenance, as we all know, usually costs much more than the initial development.

A more recent, shorter and less pedantic style guide is “The Technical Writer’s Checklist”, by unspecified people at iTrain.org (http://itrain.org/ttwc/). Its 15 pages list 38 rules essential to effective writing. Then there’s Jane Straus’s The Blue Book of Grammar and Punctuation (2004, ISBN 0-9667221-7-5) is a large-format (8.5 x 11) volume of just 104 pages which is a practical and useful guide to improving one’s use of English.

Today it’s all about communication. Write clearly, especially when crafting comments and program documentation.

Last Buy

A lot of folks use these parts. The good news is that this obsolescence will lead to more design work and full employment for embedded developers!

Tools & Tips

“It seems simple enough; Not as "robust" as SubVersion or a real version control software (no tags/branches/etc), but easy to use to make sure you don't obliterate the wrong file at the wrong time.

“Works OK on WinXP Pro.”

Grant Sargent likes Unison: “For keeping various files in sync (home, work, removable drives etc), I recommend the Unison file sync application ( http://www.cis.upenn.edu/~bcpierce/unison/ ). Great if you don't need the revision control of subversion. Available for Linux and Windows. Open Source, works as advertised.”

Stephen Pelc responded to this statement: “Please, PLEASE, recommend to your readers that they always use at least a 4-digit year (when naming files)” with: “Please also could USAnians use unambiguous dates! 5/7/2007 is a menace, whereas 05 July 2007 or 07 May 2007 are not.

“A practical date coding scheme for change notes in source code
we have found is to use:
“ date marker comment
“e.g.
“ 20070219 SFP003 Sent off to JG for newsletter
“These are in reverse chronological order at the top of the file.

“Because the date code is numeric it can be easily sorted. The marker is used in comments in the source and identifies the author (three letters) and change number (three digits).”

Oliver Bachmann writes: “If you are looking for a good search tool, try InfoRapid Search And Replace. It has one of the fastest search engines I have seen so far, and I use it regularly for searching strings in files even in subdirectories where other search tools do not generate a hit.”

Book Review

Now there’s a book about putting the OS into firmware. “Embedded Linux Primer, A Practical Real-World Approach” by Christopher Hallinan is one of those few books whose contents exactly match the title. It makes no attempt to introduce Linux to newbies, and is entirely focused on getting Linux running on an embedded system.

The chapter on building the kernel is interesting by itself as it gives some insight into how Linux is structured. Out of general curiosity I would have liked more information, from a higher-level perspective, but this is how-to tome instead presents the details needed to do the work.

A long section on processors was not particularly useful. A lot of CPUs will run the OS, and the author doesn’t point out particular advantages or downsides to any of the choices presented.

Bootloaders, including details of the ever-more-popular GRUB get good coverage, as does Linux’s initialization sequence so one can understand what’s going on as it spits out those 100+ lines of sometimes cryptic startup dialog.

The chapter on writing device drivers is short and could have been fleshed out in more detail, but does work through a useful example.

Most of the chapter on tools is too abbreviated to be of serious use to serious users of gdb and the like. But the chapter on debugging the kernel is worth the price of the book. Better, there’s a section about what to do if your gleaming new OS doesn’t boot.

Real-time issues are a real concern to a lot of firmware folks, and the author does a great job explaining both the problems, and the solutions, including some profiling data to get a bit of tantalizing insight into what sort of latencies are possible. Unfortunately, the author doesn’t list the platform, so one is left wondering if a 78 usec worst-case latency applies to a 3 GHz Pentium… or a 100 MHz ARM.

This book is not a beach read. It’s complex stuff. You’ll have a hard time finding many pages that aren’t crammed with directory listings, code, make file extracts, and the arcane argot of those delving deep into Linux. But the author writes well and informatively. If you’re planning to stuff Linux into your embedded system, get the book.

Jobs!

Joke for the Week

"The new US stealth fighter, the F-22 Raptor, was deployed for the first time to Asia earlier this month. On Feb. 11, twelve Raptors flying from Hawaii to Japan were forced to turn back when a software glitch crashed all of the F-22s' on-board computers as they crossed the international date line. The delay in arrival in Japan was previously reported, with rumors of problems with the software. CNN television, however, this morning reported that every fighter completely lost all navigation and communications when they crossed the international date line. They reportedly had to turn around and follow their tankers by visual contact back to Hawaii. According to the CNN story, if they had not been with their tankers, or the weather had been bad, this would have been serious."
http://www.dailytech.com/Lockheeds+F22+Raptor+Gets+Zapped+by+International+Date+Line/article6225.htm