Embedded Muse 158 Copyright 2008 TGG March 25, 2008
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EDITOR: Jack Ganssle, email@example.com
- Editorís Notes
- Tin Whiskers
- Response to Great Engineers
- War Story
- Tools and Tips
- Free Stuff
- Joke for the Week
- About The Embedded Muse
Did you know it IS possible to create accurate schedules? Or that most projects consume 50% of the development time in debug and test, and that itís not hard to slash that number drastically? Or that we know how to manage the quantitative relationship between complexity and bugs? Learn this and far more at my Better Firmware Faster class, presented at YOUR facility. See http://www.ganssle.com/onsite.htm .
Are you in the Chicago or Denver area? Iíll present a public version of the Better Firmware Faster class in Chicago and Denver, on April 23rd and 25th. Registration and other info here: http://www.ganssle.com/classes.htm . Youíll earn 0.7 Continuing Education Units, learn a lot, and have more than a little fun. Sign up before March 23 and receive a $50.00 discount.
Iíll be teaching a public version of this class in London, UK, May 19. See http://www.ganssle.com/classes.htm .
The EUís RoHS standards have caused a wholesale retreat from the use of lead in solder. While their intentions are noble, the electronics industry is likely to suffer mightily since alternative solders spontaneously grow tin whiskers that can Ė and have Ė create short circuits. Much has been written about this subject and thereís little for me to add. I do recommend Howard Johnsonís discussion of the problem (http://www.edn.com/article/CA6477864.html ) in which, among other things, he makes the claim that alternative solders are actually more harmful to the environment than lead. And thereís great technical information about tin whiskers here: http://nepp.nasa.gov/whisker .
For those interested in this problem, Bob Landman sent information about a new resource: As a result of much concern on the subject of Tin Whiskers (being a much more severe problem in some applications that expected) there has been much dialogue on email between a number of interested and informed parties such as NASA, CALCE, as well as many military and telecommunications companies.
As a result of these various emails the group requested that a list server be put up to discuss areas of tin whisker issues and research.
The list server is now up and can be subscribed using the following information:
- Users can subscribe to the list by sending email to firstname.lastname@example.org with 'subscribe' in the Subject field.
- Once subscribed, to post to the mailing list, simply send email to email@example.com
- To unsubscribe from the list by send an email to firstname.lastname@example.org with 'unsubscribe' in the Subject field
List moderator is John Burke at http://www.RoHSUSA.com
Response to Great Engineers
Steve Litt of troubleshooters.com had interesting comments in response to my comments about great engineers last issue:
I contend that the guru is using a troubleshooting process. Sure, it looks to *us* like he sniffs, licks his finger and touches a node, and immediately discovers the problem, but what he really did was use a process to troubleshoot, including sophisticated use of divide and conquer. Either that or he's seen the symptom before and remembers the corresponding fix.
I'm not saying he isn't hyperintelligent -- he probably is. That's how he can, in his head, quickly devise diagnostic tests and keep a real-time mental map of what he's ruled out and what is still within the root cause scope. I'm not saying he doesn't have spectacular knowledge of the underlying technology -- he probably does. That's how he deduces what diagnostic tests prove what.
What I'm saying is this -- I've seen lots of brilliant expert builders and designers who couldn't troubleshoot their way out of a paper bag because they used no troubleshooting process. You show me a guy who can sniff, lick his finger and touch a node, and immediately discovers the problem, and I'll show you a guy using a troubleshooting process. He may deny he's using a troubleshooting process. He might be unaware that he's using a troubleshooting process. But he's using one.
This is a vital distinction because a significant chunk of technical people, and most of the nontechnical people who hire them, believe that troubleshooting productivity depends on intelligence and system knowledge alone. Belief in this myth causes ballooned MTTR (Mean Time To Repair), choosing wrong training, and bad employee/job fits.
The guru technologist, like the Olympic ice skating champion, makes the difficult look easy. But like the ice skating champion, he still needs to use the right techniques to produce the desired results. In the case of troubleshooting, that means following a process.
Andy Faithfull has his own war story:
I delayed starting my bachelors course for a year to go and work for an aerospace company and get some industrial experience. It certainly paid off when it came to practical and project work at college. Anyway, I spent most of that year building cards for a 6100 based system. The 6100 was chosen because it was available in a radiation hard form I think. The system was basically designed from the data sheets. Everything was built on prototyping boards, painstakingly wired the old fashioned way using single strand wire and soldered connections. Another project team in the company was using wire-wrap techniques to do something similar, but this was considered "new-fangled" in the 70s!
We built board after board like this. The ram boards (256 bytes x 12) had so many chips on them that we had to drill some extra holes in them and glue on a couple of DIL sockets. I also built a keypad and display unit for the beast, but it never got used I don't think. Eventually we had built all the boards that the engineer in charge had designed and the grand day came;- what would we do with the thing? Entering code was achieved with thumbwheels to set up the address and data, and a button to program the selected location. Only then did it dawn on us that some software tools might be useful as programming directly in machine code was tedious to say the least.
The enormous box of boards (now christened "Ernie" after the random number generator used by the government to draw the number of the winning government bond holder each month) sat gathering dust until one enthusiastic staff member started playing around with it. He wrote a program to play music on the thing by toggling the overflow flag, which came out to a pin. He laboriously coded up "The Entertainer", and everyone was impressed. Bearing in mind the effort that had gone into programming it, the machine was not powered down for some days. One night after everyone else had gone home, the lab cleaner asked me what the big blue box with all the lights on did. I very showily demonstrated Ernie's party piece, but something went wrong and as each note was played it seemed to get corrupted. After a couple of bars the only sound coming out was an unpleasant rasping sound. The cleaner left unimpressed, and I slunk away and pretended it never happened. So I would finally like to put the record straight after nearly 30 years. Trevor, I am really sorry. I don't know how I broke it, but it was me!
Tools and Tips
Dave Kellogg sent a veritable treasure-load of resources and links. Heís big on podcasts; being one who spends little time in the car (and less exercising!) I have few opportunities to listen to them. But his list is great:
Here are some of the free education sources that I find very helpful. A lot of these are down-loadable podcasts. (Any software engineer that is not listening to a cast while commuting or exercising is missing a chance at self-improvement and increased professionalism.) Much of this is from the broader world of software engineering, rather than just embedded. However, the skilled embedded practitioner will be able to mine lots of valuable information. Several of these sources have an Agile/Lean slant, since I find lots of benefits in that method of software development.
Agile Toolkit Podcasts http://agiletoolkit.libsyn.com/
Developer Works Podcasts (IBM) http://www-128.ibm.com/developerworks/podcast/
IT Conversations http://itc.conversationsnetwork.org/index.html
Manager Tools http://www.manager-tools.com/ (This is a MUST for me each week)
Software Engineering Radio http://www.se-radio.net/ (academic, occasionally useful)
Lean Enterprise Institute http://www.lean.org/Events/WebinarHome.cfm
IEEE Spectrum Radio Online http://www.spectrum.ieee.org/radio?date=01.07.07&segStart=1
Software Quality Engineering http://www.stickyminds.com/podcasts/
Agile Project Management http://community.featureplan.com/community/webinar_archive/
Net Objectives http://www.netobjectives.com/resources/webinars
CM Crossroads http://www.cmcrossroads.com/
Atomic Object http://spin.atomicobject.com/embedded-corner/ (Interesting embedded work)
Methods & Tools http://www.methodsandtools.com/ (A quarterly software development e-publication)
Quantum Leaps http://www.quantum-leaps.com/index.htm
Mary Poppendieck http://www.poppendieck.com/
Steve McConnell http://www.construx.com/ (of Code Complete fame)
Applied Software Project Management http://www.stellman-greene.com/aspm/
Agile Management Science for Software Engineering (David Anderson) http://www.agilemanagement.net/index.html
Dan Saks - http://www.dansaks.com/articles.htm
Jack Ganssle http://www.ganssle.com/
Software development using Theory of Constraints. http://finance.groups.yahoo.com/group/TOCSoftware/
Lean Software Development http://tech.groups.yahoo.com/group/leandevelopment/
Lean Software Development and/or Scrum http://tech.groups.yahoo.com/group/leanagilescrum/
Agile Embedded http://tech.groups.yahoo.com/group/AgileEmbedded/ (Agile techniques are low overhead best practices used to develop software. Many of the agile techniques apply to embedded software. )
Google Video http://video.google.com/videosearch?q=Google%20engedu and search on EngEdu
IT Measurement and Productivity Institute (ITMPI) http://www.itmpi.org/webinars/ (Lots of good topics about s/w development)
Joost Leeuwesteijn contributed: A really good forum for embedded stuff:
http://www.keil.com/forum/threads.asp . Not just Keil specific info, and it has great info about C166, C51 and ARM architectures. T
Gary Lynch added another ton of resources: I routinely bookmark tutorials and forums, primarily, because I find the best ones serendipitously and then can't remember them when I need them. Forums appear below. Items bulleted with 'G' are in German.
1.0 Embedded hardware
On my current project I use exclusively 8051-family parts from Silicon Labs. They offer a good forum for hardware questions: http://www.cygnal.org/scripts/Ultimate.cgi?action=intro
Ö and a German, user-sponsored forum: G http://www.c51.de/c51.de/Kommunik/Forum_frm.php?UIN=
I sometimes have to do schematic capture with Altium Designer, and rely on their forum: http://forums.altium.com/forums/ to sort out stuff that isn't in the manual.
2.0 Embedded software
My IDE is by Keil, and I sometimes consult their forum to understand its eccentricities: http://www.keil.com/forum/threads.asp
Embedded control HW/SW/etc G http://www.mikrocontroller.net/forum/
3.0 Windows, PCs, Internet, etc.
MS-Excel G http://spotlight.de/cgi-bin/newmessages.pl?maxcount=10
General Wintel questions http://www.computing.net/forums/
Even broader PC questions http://www.computerhope.com/forum/
On-line security, spyware http://forums.spywareinfo.com/index.php
Everything up to here is on the world-wide web. Then there
is the grand-daddy of all forums--UseNet. Most useful to
No employer of the Internet age has ever allowed me to access UseNet from the company LAN, but I can e-mail questions home, get answers and mail them back to myself. This may seem slow, but it's often faster than my next best option.
Jean LaBrosse, well known author of the uC/OS RTOS and several embedded books, tells me that no one can identify individual authors of his companyís code. At first I thought he meant the programmers maintain anonymity out of embarrassment of their spaghetti mess, the usual situation in this industry. Sure, we beat the stuff into submission and finally shipped a product, but we slink away from the source whose original beautiful structure devolved into anarchy and chaos.
Everyone thinks they write pretty firmware. But itís worth reading the source to Jeanís operating system. Calling it pretty is like saying Leonardo seemed to know something about art. Meaning fairly jumps off the page; itís not buried into the obscure naming non-conventions and mishmash of wandering spacing thatís more typical of this business.
Itís consistently beautiful partly because everyone writes code the same way. You canít identify the developer by coding style, simply because all use an identical style, one enforced by a comprehensive firmware standard. Thereís no variation in indentation, brace placement, or any of the other little differences that C encourages.
ďDo you guys have the code police, then?Ē I asked. Turns out that itís mostly a matter of education. Many of their people are newbies recently out of college. Once exposed to this correct-think they accept it as apparently the industry-standard way to create programs.
Surely these folks will move on to other outfits over their career. Some will succumb to the pressure to forgo any styles in the mania to ship now. Like evangelists, though, surely at least a few will espouse the benefits and bring others into the fold of standardized styles.
Iíve long believed in enforced coding standards. Yet in talking to thousands of developers over the years Iíve found that only a few percent of companies enforce any such standards. Though many do have a standard, few conform to it.
Why such resistance? In large part itís due to our self-image. Weíre like knights of old, girded for combat with the evil aggressor (the specification). Our tools are as crude as the knightís lance; usually nothing more than an editor and compiler. We win based on our ability to outwit, out-think, and out-perform the enemy. So our final product by its nature is a reflection of our superior abilities.
Using a standard, especially one as effective as Jeanís, strips our software of all signs of individuality. The result is code thatís absent of any sign of the authorís quirks and prejudices. That sounds much like being just a coder in a vast software machine, but the challenge is solving the problem, not advocating some particular spacing convention.
One wag turned the tables on me. He made an analogy between coding and writing, and asked if authors (meaning me) should write equally ďsterileĒ prose. Sputtering I protested that these were too very different things and, ah, style is in fact part of the nature of writing. Later I realized one difference between English prose and firmware is the longevity of the code. My writing is but a trifle which will soon disappear into obscurity. Firmware, though, lasts for decades. Writing is not held to any functional standard Ė it doesnít have to work, like software does.
For style guides, see:
- Jean Labrosseís guide is in his very worthwhile book Embedded Systems Building Blocks.
- Chris Lottís site has many different standards and style guides, at http://www.chris-lott.org/resources/cstyle/
- cs.washington.edu in pub/cstyle.tar.Z (the updated Indian Hill guide)
- ftp.cs.toronto.edu in doc/programming (including Henry Spencer's fun ď10 Commandments for C Programmers:)
- ftp.cs.umd.edu in pub/style-guide
The last contest was so much fun Iíve decided to run another. Answer this puzzler correctly for a chance to win a free copy of The Embedded Systems Dictionary by Mike Barr and myself: What was the first C compiler used to develop a microprocessor-based embedded system, and when was it available? Iím not entirely sure of the correct answer so please include a link or other substantiation if you can.
Contest rules: one winner only, who will be selected at random on or about April 4 from all of the correct entries; by ďcorrectĒ I mean the answer that appears to be correct (i.e., fun is more important than ultimate Truth). Send your entry to email@example.com . Sorry, we canít acknowledge entries. Iíll post the winnerís name (but no other contact info) in the next Muse and any funny or interesting commentary.
Joke for the Week
Did you ever want machine instructions like:
BRO (BRanch to Oblivion)
BRO (Branch on Power Off)
DMPE (Decide to Major in Physical Education)
EMSL (Entire Memory Shift Left)
HCF (Halt and Catch Fire)
JAA (Jump Almost Always)
OPP (Order Pizza for Programmer)
PON (Power ON)
Well, thereís a pretty complete list here: http://www.physics.ohio-state.edu/~bcd/humor/instruction.set.html