Thursday, September 11, 2008

Random Musings on is a site by programmers and for programmers, whose purpose is answering questions on topics relating to software development. At the time of this writing it has completed a closed beta test and is in a more extensive test phase, ramping up to open on September 15, 2008. Access to the beta site is open to anyone who wants it during the test period, see for details.

Stackoverflow is the brainchild of Jeff Atwood and Joel Spolsky, long-time bloggers on software development topics. It is described by its creators as the intersection of a Wiki, blog, forum, and digg/reddit voting site. Users post questions and answers about programming topics, and the questions and answers are voted on by the community. The highest voted answers rise to the top.

Incentives, aka upvoting

The site has a series of incentives to keep people coming back. The biggest incentive is the reputation score, which goes up and down depending on how other users rate your questions and answers. Reputation encourages asking questions and providing answers, in order to improve ones score.

reputation Reputation is in many ways similar to the Karma awarded by and Hacker News. Capabilities on the site are unlocked by having a high enough reputation. For example voting on posts requires a score of 15 or more, where new users start with a score of 1.

The other, more unique rewards system on stackoverflow are the badges. Badges are directly modeled after the achievements awarded in Xbox games, which encourage gameplay by granting an award when a level is completed or other objectives achieved. The achievements show up in a gamers profile on Xbox Live, where they are used to talk smack about opponents.

badges The stackoverflow badges encourage exploration of the features of the site. The first few badges area easy to obtain: fill out your profile to obtain the Autobiographer badge, vote up to get the Supporter badge, and gain the Teacher badge by asking a question which is voted up. Later badges get harder, requiring larger numbers of users to vote on your submissions.

Are these mechanisms effective? I think the reputation score is, certainly. As in a video game, there is a certain thrill to seeing ones score go up. The badges seem, well, hokey to me. I'll grant that I'm probably not the target demographic anyway, badges might have more resonance with those who play games regularly.

Content question votes

The questions during the stackoverflow beta have ranged widely, but by far the most common questions are about Microsoft topics like .Net and SQL Server. This is likely a reflection of the audience of Jeff and Joel's respective blogs being heavily invested in these technologies.

I've been pleasantly surprised by a number of the questions posed on the site. Where the programming sub-reddit is now completely dominated by Ruby, Python, and Haskell, stackoverflow is covering a much wider mix of technologies. There have even been a few embedded system and assembly language questions.

Technical solutions to social problems

The history of web communities dedicated to software developers has not been pretty. The comment section of the programming sub-reddit is now so filled with vitriol and casual slander as to be unpleasant to read, let alone participate in. Hacker News attempts to prevent this slide into toxicity by a combination of social pressure and technical measures like not allowing downvotes until a certain karma has been achieved.

Stackoverflow is relying heavily on technical solutions to social problems. For example:

  1. Downvotes are only allowed by those at higher reputations, and reduce the target reputation by two where an upvote adds ten. Additionally downvoting costs the voter one point of reputation, to discourage frequent use.
  2. To discourage trivial edits to bump a question to the top of the list, more than five edits to a post make it "community owned" and no longer grant reputation to its poster.
  3. Users with sufficiently high reputation can edit another users posts or comments, for example to remove mean-spirited remarks. It is hoped they will use these powers for Good and not Evil.
  4. Users can mark a question or answer as offensive. This does not merely signal a moderator; if enough users click offensive the question will be automatically removed.

Speed bumps coming

I really like the premise behind stackoverflow, of a social media site designed specifically for programmers. I think there is definitely a need which reddit, DZone, and other developer-focussed sites do not fill.

Editing another users post

However I think this initial iteration of stackoverflow has a psychological problem: it tries to simultaneously be a voting site like reddit and digg, and a community site like Wikipedia. What you end up with is postings associated with a particular users name, and which provide benefits in the form of reputation, but which can be edited by other users. The site attempts to ameliorate this by making a post "community owned" after five edits, so it no longer belongs to the posting user. This step function solution brings the opposite problem: the poster feels cheated out of the reputation from what has become a popular topic.

This mismatch between the digg and wikipedia models is not working smoothly yet, in my opinion. The digg model thrives on ownership, the wikipedia model on anonymity.

Some other thoughts about future issues:

  • On other sites even replying to someone else's comment can elicit a defensive reaction. I suspect that editing another user's question or answer on stackoverflow will lead to a series of edit-revert-edit-revert struggles.
  • There is an enormous incentive to answer quickly: the early answers accrue upvotes and gain significant inertia to accrue more upvotes. A number of users answer immediately by quoting Wikipedia or the first Google result, and gain significant reputation by doing so. stackoverflow will have difficulty succeeding if the highest rated answers are mostly Wikipedia rehashes.
  • The site is far more active during US business hours, and relatively idle during nights and weekends. When combined with the strong incentive to answer immediately, the site can become a productivity drain. We may see companies block stackoverflow in the same way that Facebook is often blocked.


I really like stackoverflow, and I want it to succeed. I think its business model is sound: focus on a well-defined niche, provide real value, and carefully select advertising to target that specific audience.

UPDATE: This article was picked up on reddit, with amusing commentary. Also Sara Chipps and Dan Dyer have written about their initial impressions of stackoverflow.

Wednesday, September 3, 2008

The Good, Bad, and Ugly of Gizmo Construction

Rather by definition, embedded software involves building a gizmo of some sort. Manufacturing the hardware portion of the gizmo turns out to be somewhat more complicated than writing a Makefile and starting the build... who knew?

Today, Gentle Reader, we'll discuss the realities of building hardware products by meandering through a few topics:

  • Contract Manufacturing
  • Distributors
  • Contract Engineering
  • DVT and Compliance

Contract Manufacturing Printed Circuit Board

Contract manufacturers build a product according to a completed design including the Bill of Materials, the layout of the printed circuit board, assembly instructions, system tests, etc. They can do as much or as little as desired, from a single board up to a completed and tested system directly shipped to your customer.

In the last 25 years contract manufacturing has essentially taken over the production of all electronic goods. The economies of scale from producing such large volumes are overwhelming, and there are very few companies who maintain their own production facilities now. The capital expenses for kitting out an assembly line are daunting, the CM can amortize the cost over a huge number of products. Some well known contract manufacturing firms are Foxconn (also known as Hon Hai), Flextronics (which owns Solectron, another large CM), Celestica, and Sanmina-SCI.

Contract Manufacturers thrive on volume. If building something in really small volumes it is worth looking into production shops aimed at hobbyists, such ExpressPCB.

One thing to keep firmly in mind: the value of a customer to a CM is measured entirely by the volume of future business they expect. If order volumes drop off, the CM will rapidly lose interest. If your market suffers a serious downturn you may find that the quality of the product drops precipitously as the CM rushes through the build in order to get to another, more profitable customer. Similarly if you decide to terminate business with a CM and move to a competing firm, expect astonishingly bad build quality on the final order.

Distributors Fistful of Dollars

Like it or not, distributors are absolutely necessary in the embedded market. There are tens of thousands of customers buying millions of components. The component manufacturers simply cannot afford to maintain individual relationships with each customer when a distributor can represent multiple manufacturers with the same effort and expense.

Many Distributors provide FAEs (Field Application Engineers) to assist their customers in selecting components. A good FAE is extremely valuable, due to the sheer number of product designs they have been involved in. They will often be able to suggest alternatives which you might not otherwise have found, and know which parts have been problematic in other designs.

Distributors and Registration

Distributors who perform a significant amount of technical support during the design of a product cannot allow themselves to be undercut by a cheaper alternative in production. Therefore the component manufacturers allow distributors to register as being responsible for the design win at a particular customer. Only that distributor will be allowed to offer advantageous pricing, other distributors will not be allowed to undercut them.

Distributors do a lot more business with the big Contract Manufacturers than any individual customer, and CMs value their relationship with the distributor more than any individual customer. It is not unknown for a Distie to legitimately claim the design win for one particular component, then obtain the Bill of Materials from the CM and register themselves for every chip in the design. Choosing a Distributor is much like getting married: be very certain that the relationship will work in the long term before signing on the dotted line.

Contract Engineering Schematic

For a niche market with well-defined needs, a product can sell for years with minimal changes. In these cases its better to contract out the design than recruit a team. The contract will include the functional spec to be designed, timelines for completion, etc. The engineering firm will supply the requisite hardware, software, and firmware expertise, and the resulting design will belong to the customer.

Alternately, Contract Engineering firms can fill in gaps for an in-house design team. For example after components have been chosen and the design competed, a layout for the printed circuit board must be created. A good layout of a complex PCB requires an experienced designer and expensive CAD tools. It makes no sense to keep such a person on staff if only a few designs are done each year, so it is often contracted out. Mechanical design of the chassis and other sheet metal is also often done outside, for the same reason.

Contracts in this area are essentially always on a time and materials basis. The upfront estimate of total cost is not guaranteed. Fixed price contracts are exceedingly rare, because they represent an enormous risk to the engineering firm if the design time goes over estimates. In most cases this will work out fine: the engineering firm will want to get the design done quickly in order to move on to the next customer. However if business slows, watch out for unjustified padding of billable hours.

Design Verification Test Eye pattern

Not every unit coming out of the factory will be identical. Each component in the design has a tolerance, an allowed deviation which is still considered within specification. Every system coming off the line will contain parts slightly above spec or below, and it is important to insure that the complete system will still function reliably even if it contains components at the extreme ends of the tolerance. Though the hardware design takes these tolerances into account, in the real world it is difficult to anticipate every possible interaction of components and PCBs.

This is where DVT, for Design Verification test, comes in. During DVT the hardware engineers measure the system to ensure it not only does what it is supposed to do, but does so with sufficient margin to handle variances in its components. DVT is time-consuming work, and changes are often made in the production system based on what is found in the prototypes.

Compliance Underwriters Laboratories

The ubiquitous Underwriters Laboratories logo is likely the most widely known example of a compliance certification, but it is not the only one. There are a huge number of standards for product safety or performance, some recognized around the globe and others specific to each geographic market.

Some industries place much more stringent requirements on their products than others. For example, the NEBS Level 3 guidelines for the telecommunications market specifies that there be no noxious chemicals released if the equipment catches fire.


One of the aims of this blog is to provide insight into fields of software development which don't get as much exposure as Ruby on Rails or web frameworks. I've tried to provide an overview of some of the gritty details of building products. Its really quite exciting when the first prototype of a new system comes back from the factory, and you try to boot the software for the first time. When it doesn't boot, reality hits.

I'd like to thank John Walsh for much feedback and good suggestions of topics to cover in this posting.