The Embedded Muse The Embedded Muse 159
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1. Chaucer s olde english is just that trying For example For oute of olde feldys as men sey Comyth al this newe corn from yere to yere And out of old bokis in good fey Comyth al this newe science that men lere On coding standards and code reviews You omitted to mention the MISRA software Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com guidelines which I think are an excellent example of guidelines developed specifically for embedded systems As you know MISRA The Motor Industry Software Reliability Association published the Development Guidelines for Vehicle Based Software a remarkably compact collection of software development rules hat aid in the development of reliable and safe software for vehicle based software I tried establishing coding standards in a former workplace and was met with resistance from my coworkers and friends when I was their supervisor The parties involved could not agree on conventions rules and standards even when some good third party standards and guidelines such as the MISRA guidelines mentioned above were available I did not want to be authoritative so I backed off for the greater good as seen by the company the output of code rather embedded code which in turn went into a product that was itself shipped The company s focus on code to2. a BS degree and 4 or more years experience designing and implementing sophisticated software systems excellent proficiency in C language with exposure to C and or Java language a thorough working knowledge of Linux operating systems and experience developing and debugging with the GNU tool chain Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com If you are a bright career minded individual with a passion for technology we want to hear from you Please email your resume and cover letter to careers goahead com All qualified applicants are encouraged to apply Joke for the Week No joke this week Instead here is a compendium of funny instructions and other tidbits folks sent in response to last issue s link to amusing mnemonics From Tom Paden But your humor spot has a bit of truth in it The early 6800 had an undocumented test op code called HCF Halt and Catch Fire It would fetch from consecutive memory locations to test out the address bus I forget how I found out about it but it s documented on Wikipedia http en wikipedia org wiki Halt_and_Catch_Fire Chris Nelson wrote An early mainframe OS at RPI had a joke language called Screwbol if I recall correctly which actually implemented HEO Halt and Eat Operator When executed this instruction caused the big line printer t
3. help out in the one field I know and love Today I continue to write and continue to try to educate berate and encourage embedded developers and their managers to improve their techniques A couple of companies asked me to come in and provide training about firmware development Well high school speech class was a trauma I was terrified of talking in front of anyone a fear that persisted into my 30s But as a personal challenge I had decided to get over this irrational dread and took some speaking classes and then practiced When the Embedded Systems Conference was born they asked me to give a talk and I found it an exhilarating experience What fun to interact with all of these very smart people It seemed natural to develop a seminar that would help folks get better code faster Over the last decade ve given the seminar to hundreds of companies and thousands of developers No one is naive enough to think there s a silver bullet that will solve all our problems This field is intrinsically tough Even if we knew how to generate 10 million lines of perfect code in a day customers will scream to shorten the schedule to an hour But it is possible to create better code faster It is possible to drastically reduce bug rates and shorten schedules Those two do go hand in hand Capers Jones showed that bugs are number one cause of missed schedules For example there s an approach that drives the usual 5 10 pre test bug rate
4. machines before them especially the big one per campus installations in restricted access raised floor air conditioned rooms used to feature line printers with 132 hammers impacting upon fan folded paper tractor fed past a foot wide ribbon and a spinning drum of type The whole thing was bigger than a jukebox You know what a jukebox is right It played 45 s you know vinyl records with grooves Never mind About The Embedded Muse The Embedded Muse is an occasional newsletter sent via email by Jack Ganssle Send complaints comments and contributions to him at jack ganssle com To subscribe send a message to majordomo ganssle com with the words subscribe embedded your email address in the body To unsubscribe change the message to unsubscribe embedded your email address BUT please use YOUR email address in place of email address The Embedded Muse is supported by The Ganssle Group whose mission is to help embedded folks get better products to market faster We offer seminars at your site offering hard hitting ideas and action you can take now to improve firmware quality and decrease development time Contact us at info ganssle com for more information Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com
5. The Embedded Muse 159 Editor Jack Ganssle jack ganssle com April 7 2008 You may redistribute this newsletter for noncommercial purposes For commercial use contact info ganssle com EDITOR Jack Ganssle jack ganssle com CONTENTS Editor s Notes Response to Great Engineers Tools and Tips Styles Jobs Joke for the Week About The Embedded Muse Editor s Notes 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 it s 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 classes htm Are you in the Chicago or Denver area IIl present a public version of the Better Firmware Faster class in Chicago and Denver on April 23 and 25th Registration and other info here http www ganssle com classes htm You Il earn 0 7 Continuing Education Units learn a lot and have more than a little fun ll be teaching a public version of this class in London UK May 19 See http www ganssle com classes htm Robert Michael won the Muse 158 contest by naming the first embedded C compiler at least this matches my memory A recent taped interview with P J Plauger the founder of Whitesmiths taped for the upcoming Embedde
6. d Systems Conference confirms the date Robert wrote I have no way to substantiate the date but at TRW Vidar I used the Whitesmith C compiler to generate 8080 code to control the embedded processors on the Vidar ITS class 4 5 digital telephone switching system in 1978 We used Unix version 6 Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com on a PDP 11 60 with the Rand 50 changes enhancements in cross compiler mode Shameless Promotion In 1971 Intel invented the microprocessor but few knew what to use it for Even Intel predicted a tiny market for the device But they persisted and the following year came out with the 8008 the first 8 bitter Companies quickly realized how adding a bit of intelligence to their products reduced costs and increased functionality The embedded systems industry was born I was in college working as an electronics tech at a small outfit named Neotec but was the only employee at the company who knew anything about programming We had been using a consultant who remains in occasional contact They tapped me to be their first in house firmware developer Though it was easy to master 8008 assembly language my software engineering skills were null This was typical of the industry All early embedded people had been trained as EEs not computer scienti
7. d at the question I plugged a test telephone into a jack on the noise meter designed for that purpose Listening to the telephone I heard the distinctive sound of 60 Hz hum and found that the field of the power transformer was coupling into the system s wiring Old guys in that business had previously advised me to listen to the line And on that day I became an old guy Standards My comments on standards provoked a lot of replies Christoph Schmidt wrote If you want to enforce common indentation spacing in C code try GNU indent http www gnu org software indent To comply with coding standards like MISRA C I would recommend PCLint FlexeLint http www gimpel com which can check for a wide range of rules as well as common pitfalls Unfortunately I haven t found an open source alternative yet As it is a commercial program it comes with some license cost splint http www splint org is an open source LINT but I does not like it that much Do you know any other open source LINT For commenting I use doxygen http www stack nl dimitri doxygen Not just for creating some nice formatted documentation of my code but also to ensure that everything is commented and the identifiers in the code match the ones in the comments Using these three tools I can focus on writing correct code and meaningful comments without need to study the coding guidelines every few minutes except for naming conventions Using t
8. day and legacy support later led to archives of undocumented code in varying styles that had to supported possibly for decades by people other that the original designer Your example standard outlines this last concern is where it says that software should clearly communicate how it works to a future programmer or the future version of yourself In the same working environment I also tried establishing code reviews These were also met with resistance from my coworkers for the reason that when one critiques another s work it is seen as criticism and is not received well I tried to remove this interpersonal dynamic through the use of third party code tools similar to pc lint But again there were objections to the rules used by the code checkers and some of the rules were disabled making the tools ineffective And again these efforts were set aside as they were seen as interfering with the output of code Jobs Let me know if you re hiring firmware or embedded designers No recruiters please and I reserve the right to edit ads to fit the format and intents of this newsletter GoAhead Software located in a Seattle suburb is changing the face of high availability and system management for the telecom military and aerospace industries Currently GoAhead is seeking a Software Developer to join its technical team This position designs develops documents and tests software for a variety of operating systems Qualifications include
9. ding style and my philosophy is understood and accepted by all the software engineers in the company The younger people actually expect this based on what they re being taught in their university courses They would be astonished if we didn t have such a standard To ensure compliance with the standard our code inspections have a defect category for non conformance to coding standards A missing white space character will be tagged as a code defect in this category and this defect will have to be corrected before the code may be released Engineers who believe that coding standards crush creativity are completely wrong I Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com want my staff to be creative in ways that matter such as their choice of algorithm I don t want them to waste time being uselessly creative in trivial matters such as where to place a curly bracket or how many characters to indent a line of code gt One wag turned the tables on me He made an analogy between gt coding and writing and asked if authors meaning me should gt write equally sterile prose I ve heard this before and it s bogus Much of style is about consistency of layout English language style guides specify that we should all start sentences with a capital letter use paragraphs use common pu
10. down by three orders of magnitude Though I mention it in the seminars I don t teach the technique as few of us for a variety of reasons will ever embrace it That seems odd Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com perhaps but my interest is showing methods that most of us can start using immediately to get dramatic improvements And that s the entire thrust of the seminar What can we do today in a stealth fashion under the scope of management s radar to get better code faster What can we do without embracing some monster methodology that few will really use that requires a revolution in the engineering department that probably won t happen What can we individuals do now to improve our performance That s my passion I m frustrated with consumer products that don t work well with safety critical code that isn t with a situation where every three year old knows if something electronical acts odd cycle power Can t we find ways to meet the schedule We can I ll show you how If you want more details and the usual marketing hype see http www ganssle com classes htm Most of the time I present the seminar on site when a company asks me to come in for a day Occasionally I do a public seminar at a hotel We have decided to do public seminars in Chica
11. er project and indeed if your company is essentially one flagship program an OS say then you might more easily have a company wide coding standard But for shops that ship some number of unrelated independent firmware projects whose clients or even whose programmers may never see each other s work arguments about degrees of refinement in coding style can seem like costly indulgence Of course I do have a highly evolved coding style still evolving in fact after 30 years with many opportunities to revisit my earlier selves and I believe it contributes to my productivity by framing my intentions higher level constructs than the native programming language contains in ways that are captured and manifest in the source text I am just now trying to foist these ideas upon my son now taking his first programming class in engineering school and his final grade as well as future use of the skills will tell me how right I am From Down Under Geoff Patch wrote Firstly I agree about Mr Labrosse and his code The source code to uC OS is magnificent and has been an inspiration to me for many years When I joined CEA every engineer wrote code using his we were all guys then own style I could open up a file in Emacs and immediately know who had written the code and I always thought that this was A Very Bad Thing Since taking over as the head of the Software Engineering group I ve implemented and vigorously enforced a standard co
12. es what should be only an interim lack of understanding 2 You can t solve the problem if you don t understand the problem If you throw fixes at a problem until the problem goes away aka The Shotgun Method you haven t really solved or learned anything Once you understand the cause the solution should be immediately evident even if that means starting from scratch If what you try does not succeed rework your understanding until it is in syne with reality What makes the guru process seem mysterious is that the What to do dialog is running internally and silently what s the point of getting advice from someone that s just spent a week debugging a circuit with the power supply unplugged I have also found that I get a perverse pleasure from estimating the number of seconds I ll spend figuring out their week long puzzle but that s just me Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com Another reader who wanted to keep his name private wrote While working on a rack mounted telephone system our company was building the technician on the production floor called me out because in one of the system checks the noise meter was reading was too high At first we could not determine the reason for the noise reading until I asked what kind of noise was present The technician was puzzle
13. gineers Response John Taylor had some good thoughts in response to this from Steve Litt in the last Muse 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 He wrote I ve had people put off asking me for help until the panic sets in just to avoid me making them feel stupid when I touch the node It really is a process to be sure and one that actually begins long before I get to the bench When someone comes to my office with a problem I always start with two simple questions What is it doing and what is it supposed to be doing I usually have to squeeze the answers to those questions out of them but I m not getting out of my chair until they do On the walk to the bench or the drive to the office I m already working out in my head what I plan to measure or which component I plan to smell and then what to do if my first guess comes up empty These are the two rules by which I trouble shoot and design 1 There is no magic Every problem has a cause and that cause can be discovered through analysis of the system operating conditions and symptoms The word Mysterious must never be used in the final analysis this word describ
14. go and Denver this month and London in May About half the participants fly in the others tend to be local Please join us it s a jam packed but always fun day I guarantee you ll learn a lot all of which is backed up with hard numbers you can take back to the boss and your colleagues But seats fill quickly If you re looking for more hands on in depth training especially targeted at getting less experienced engineers up to speed in developing embedded apps consider Netrino s five day Embedded Software Boot Camp which consists of a concentrated series of lectures and hands on exercises There s more info here http www netrino com Embedded S ystems Boot Camp Tools and Tips Dan Swiger wrote In your next to latest Muse a reader asked about forums You provide a remarkable list in EM158 but I had one that I didn t see in there If you are a user of the SlickEdit editor AWE SOME then the Slick Edit community forum is great http community slickedit com The developers are very active in the forums and you very often find ways to enhance your use of the product There are so many features in the editor it is simply unbelievable and reading through the forums is a great way to learn new techniques Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com Great En
15. hese tools in groups produces a quite similar coding style especially with new programmers which are not used to the coding guidelines yet Pete Klammer said only a few percent of companies enforce any such standards Though many do have a standard few conform to it Why such resistance This reminds me a little of my impression of ISO 9000 it doesn t require any particular method or process but rather requires that your particular method or process be well specified and documented and adhered to with consistency Since there is no widely shared consensus on any single coding standard there will Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com inevitably be a variety of favorites amongst the staff as employees come and go Since there is usually no definitive rationale for one style preference over another much time energy and ego can be expended trying to resolve disputed preferences While this examination might indeed be edifying and the unexamined life is indeed not much worth living the company is not paying for philosophy and this project has to ship by Friday or else Meanwhile the losers of such contests are more likely to feel abused than converted and less likely to feel comfortable sticking around It s easier to contemplate a coding standard per product or p
16. nctuation etc Within those style guidelines you can write everything from a user manual to a poem without having your creativity hindered Using standard style enhances both ease of expression and ease of comprehension of source code If every engineer used a different style it would simply hinder comprehension by other engineers James Thayer also had something to say about styles in writing prose As it happens many employers of authors and writers do impose a style guide for work that they publish The reasons stated for doing so sound very similar to the reasons that it makes sense to have style guidelines for software One resource for style guidelines for authors is http www library fordham edu res_guid StyleGuide StyleGuide html In short perhaps coding and writing are not so different after all I would also argue that in neither case does a style guide make the work sterile Seriously if anyone thinks that their creativity is stifled by how they place brackets or how they name their variables they are probably in the wrong line of work I d much rather have someone working for me whose creativity is expressed in the way that they solve problems than in the way that they type their code A reader who wished to remain anonymous sent this You said Later I realized one difference between English prose and firmware is the longevity of the code I agree and would add that while notable to many academics I would say that trying to read
17. o open the access door then slam the write head back and forth to cause the printer to walk across the floor toward the operator console Then there are these from Stephen Irons The ones I always tried to avoid were from Motorola s 6803 microcontrollers BHT Branch if High Tide BLT Branch if Low Tide These were real instructions for at least the 6803 and I think for the whole 6800 series The real meaning if I remember correctly were Branch if Higher Than and Branch if Lower Than using an unsigned comparison as opposed to BGT and BLT greater than and less than which did a signed comparison From Gary Gaebel Your Joke brought to mind some similar hardware devices The permistable multivibrator great when you need a constant output signal Saves on pin count too no input pins needed The 9046 x N random access write only memory chip I actually have a spec sheet for this one And lastly the Quad Two Input Maybe Gate Apply any combination of 0 s and 1 s to the two input pins and maybe you ll get a O on the output or maybe you ll get a 1 Think Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com random number generator From Peter Klammer One of my favorite opcodes was always LDCR line of dashes cut ribbon For the younger generation computers and tabulating
18. omething interesting ALL of us had the same problems Little groups of engineers all used heroics and nearly all delivered late Ironically we who invented the communications age didn t talk to each other So we all Copyright 2003 by The Ganssle Group All Rights Reserved You may distribute this for non commercial purposes Contact us at info ganssle com for more information The Ganssle Group www ganssle com faced the same sorts of challenges thinking that we were doing something wrong and that other teams had the secrets to success I studied software engineering The field all but ignored by firmware folks had a great body of accumulated wisdom Frustrated with the state of our practices in 1988 I started writing for various electronics embedded publications about technical issues and better ways to develop code Over the years I ve had the honor of serving on a number of boards including one technical college and was even tapped to teach engineering In those cases it was shocking to see that too many schools push the same old dysfunctional software methods here s how a for loop works Now write some code A dozen years ago I sold the emulator business and tried retirement After one day it seemed a rather bleak and meaningless state so looked for something interesting to do something which could be of benefit to others Turns out I m clueless about most traditional philanthropic activities so decided to try and
19. sts 30 years of lessons learned in the software business were ignored by this fledgling industry Programs were small and management clueless about software projects But the 8008 had a max address space of 16k so hacking was reasonably effective Projects grew in pace with expanding address spaces offered by the 8080 8088 68k and more Feature sets exploded Complexity skyrocketed Glass claims that for every 25 increase in features complexity grows by 100 a number that s hard to dispute At Neotec we reacted in the usual manner Hired more people Worked longer hours Made promises we never fulfilled And of course shipped plenty of bug fixes to irate customers I eventually left and started a consultancy with a partner What a ride we had What fun it was to put our gear in say a steel mill with a hundred foot long piece of 2000 degree steel four inches thick moving at a breakneck pace That used a PDP 11 and a number of Z80s Or systems that lived 10 000 feet deep in the ocean running on a few AAs for a year RCA 1802 Then there was the White House security system over 100 8085s which we designed and installed during the Reagan years After too many late nights we started to sense that there were better approaches than our usual heroics But what was wrong with us Why were we working so hard Then I started an in circuit emulator company Now providing tech support to embedded developers all over the world I discovered s
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