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Issue Number 244, September 3, 2013
Copyright 2013 The Ganssle Group

Editor: Jack Ganssle, jack@ganssle.com
   Jack Ganssle, Editor of The Embedded Muse

You may redistribute this newsletter for noncommercial purposes. For commercial use contact info@ganssle.com. To subscribe or unsubscribe go to http://www.ganssle.com/tem-subunsub.html or drop Jack an email.

Contents
Editor's Notes

Ad

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/onsite.htm.

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Quotes and Thoughts

"Learning to program has no more to do with designing interactive software than learning to touch type has to do with writing poetry." - Ted Nelson

Tools and Tips

Please submit neat ideas or thoughts about tools, techniques and resources you love or hate.

In response to last issue's discussion about visualizing code, Ryan Macaluso wrote:

For code visualization, Doxygen does a decent job for free to show you your function hierarchy with the help of Graphviz.  Klocwork used to have a product called Architect that would do something similar but it doesn't look they provide it any more or it is bundled with Insight.

A number of readers mentioned UML, and Dave Meekhof mentioned Miro Samek's tools.

Rich Hardenstein uses an open source visualization tool called Gephi. He included a fascinating .PDF he created with Gephi that shows how Internet RFCs containing the string "IPv6" are related, but it is too big, and too deep, to include it in the Muse.

What I'm Reading

The demise of vacation bodes ill for American workers.

Did Grace Hopper coin the word “bug” to mean a mistake? Seems Thomas Edison got there first.

Old Eval Boards

Last issue I relayed a question from a reader about what we can do with those big stacks of old eval boards that pile up. Bandit wrote:

A couple of good places to send eval boards:

- any school with a robotics class

- the local hackerspace - see hackerspaces.org for a list/map

John Johnson suggested:

I would suggest that, in lieu of a willing school or charity, Bob [or anyone reading your newsletters] could donate any development equipment or tools to their local makerspace.

Makerspaces, otherwise known as hackerspaces, are collectives where like minded people collaborate of projects ranging from robots, suits of armour, 3d printers, flying machines, etc. The makerspace of which I am a member is the KWARTZLAB which can be seen at http://www.kwartzlab.ca/.

As there are makerspaces all over the world I do not think that Bob or anyone else will have trouble find a local makerspace.
There are a few directories such as:
http://makerspace.com/makerspace-directory and
http://hackerspaces.org/wiki/List_of_Hacker_Spaces

Steve Karg donates them to a robot club:

When I had development kits that I no longer used, I gave them away at AHRC meetings (Atlanta Hobby Robot Club):
http://botlanta.org/ .

Small Parts

The title of this section is "Small Parts," which immediately made me think of a great source for small mechanical bits and pieces: Small Parts Inc.

Another fabulous place to get just about any kind of mechanical component, from bolts to metal stock to welding gear, is McMaster-Carr. I order from them constantly. If you're in the USA and within 150 miles of one of their warehouses, have the parts (which are always in stock) shipped UPS ground. It's cheap, and they show up the very next day.

But those non sequiturs aside, electronic parts sure are getting small. A couple of linear voltage regulators showed up from Analog Devices last week. These ADP172 devices come in Wafer Level Chip Scale Packaging (WLCSP) and are truly tiny. They measure 1 mm square and have just four connections:

Small Part

Similarly, NXP just announced their LPC81x series, which are ARM Cortex M0+ MCUs in, among other configurations, an 8 pin package. Alas, that's a DIP, which is nice for experimenting, but not so great for production. I believe Microchip still wins the smallest MCU award as they offer parts in a 6 pin SOT-23 configuration.

In the "bigger is better" department, a friend called the other day wondering if I had any low-voltage inverters laying around for a quick experiment. Nope. So he realized he had two options: order a $0.20 part and pay a minimum order amount, plus shipping, and wait for delivery. Or, use an MSP430 16 bit CPU eval board he had. Think about it: not that long ago no one could afford computers. Now we consider using them to invert a single digital bit.

Do The Math

We're all superprogrammers. Or at least perform in the stratospheric top quartile of developers. Maybe Joe Coder down the hall is "average," but us? We're the tops.

Somehow we make this assessment based on a qualitative feel driven more by ego than hard data. Nothing costs more than firmware, yet no other industry manages productivity so poorly. That used car salesman with the crooked teeth and untrustworthy smile watches his sales numbers like a hawk. The widgets we design are manufactured in a facility that tracks defects, rework, worker productivity and more, usually with graphs posted in the halls so everyone knows just how well things are going.

But us? We'll work hard. Real hard. It'll be done when it's done.

Many classical software estimation techniques naively yet wisely expect developers to design the software, decompose it into modules, and then figure the number of lines of code for each module. Then we solve one of the most interesting equations extant:

Schedule = (lines of code) / (lines of code produced per month)

... when no one has a clue as to the size of the second term. Is it 50 lines/month? 500? 5 million?

At this point the usual chorus waltzes in from stage right to complain that "lines of code" (LOC) is a very poor metric, subject to huge variations depending on styles and more. Academics, especially, fault the LOC metric and generally advocate some form of function points as a replacement. But, in industry, no one uses functions points, so if I tell you a routine will be 50 FPs you'll have no gut feel for the module's complexity. If, on the other hand, I tell you it's 2500 LOC you'll have that visceral understanding of its complexity. If tomorrow a charismatic leader took over the country and told us all gas mileage calculations will be figured in furlongs per dram, well the numbers will be just as accurate as liters/kilometer or gallons/mile, but will baffle consumers. Familiarity has value.

Oddly, the literature is full of conversions between function points and LOC. On average, across all languages, one FP burns around 100 lines of code.

Sometimes the Function Point debate is merely FUD tossed in to avoid the real issue -- that of measuring something, anything to get some kind of assessment into our productivity numbers. There are many ways to measure productivity; two companies I know quite literally monitor network traffic to log keystrokes per hour. Those engineers write a lot of long-winded comments.

Why take such data? If we're lucky enough to have the time to decompose a problem into subunits and LOC before estimating, then the numbers give us a reasonable shot at coming up with a realistic schedule. Barry Boehm has shown us that the schedule is proportional to the number of thousands of lines of code raised to an exponent. His Constructive Cost Models (COCOMO and COCOMO II) gives various exponents and scaling coefficients to predict development time of various kinds of software.

But even when we're just furiously coding to a capricious deadline tracking LOC/hour tells us, when measured over the long term, if we're improving, or just stagnating at our efforts.

The Wal-Martization of software development means Joe Coder sitting comfortably in downtown San Jose is competing directly with a very smart, highly trained developer a half a world away, thrilled to work for just a fraction of Joe's salary. If we're not constantly becoming more productive we'll be retreads on the grinding wheel of global business.

Track LOC/hour, measuring total time invested from the beginning of the project till the day it's finally done. That encompasses a lot more than coding and debugging... but all of the other development activities are real costs more or less proportional to the size of the project.

Track project size as well. You might crank 200 LOC/month on a 100k LOC project, but your rates will be much higher for smaller systems.

And log bug rates. It's easy to write lots of buggy code fast.

Artists work by feel. Engineering is about collecting and understanding the numbers.

Jobs!

Let me know if you’re hiring embedded engineers. No recruiters please, and I reserve the right to edit ads to fit the format and intents of this newsletter. Please keep it to 100 words.

Joke For The Week

Note: These jokes are archived at www.ganssle.com/jokes.htm.

Thomas Osbrink sent this bit of brilliant engineering:

Bug

 

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The Embedded Muse is Jack Ganssle's newsletter. Send complaints, comments, and contributions to me at jack@ganssle.com.

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.