Making Embedded Systems

Chapter 10. Reducing Power Consumption

Whether you are building a device that fits in your pocket or trying to save the world by reducing your company’s carbon footprint, decreasing a system’s power consumption can take an order of magnitude more time than implementing the product features. Choosing all the right hardware components is a huge part of making a system power-efficient. But because the processor is likely to be one of the largest consumers of power in the system, software can play a big role in saving electricity.

The pressures to decrease power usage and cost are what lead us to select processors that don’t have enough resources to comfortably perform the product features. Since you are a relatively expensive resource, using your time to save on cost of the processor is sensible only if you are building enough units to amortize your time.

Tip

How expensive are you? Take your annual salary and divide by a thousand. That is about what each hour of your time costs your company, counting salary, benefits, office space, and all the little things that add up. So if you are making an example salary of $1,000 per year, each hour is worth about $1. If you can buy a $3.50 tool to tool to save four hours, it is usually worth it. Of course, there is a difference between capital outlay (cash) and sunk cost (your salary), so although this is a good rule of thumb, your boss might not let you buy the scooter to get from your desk to the break room, even after you describe the cost benefit ...