Extreme Processing Thresholds: Energy Estimation and Measurement

Friday, April 30th, 2010 by Robert Cravotta

 [Editor's Note: This was originally posted on the Embedded Master

Low power operation continues to grow in importance as a product differentiator. One of the most visible examples of the importance of low power operation is chronicled in the success of the Nintendo Gameboy which debuted in 1989. It was not the most technically advanced product of its type. It did not have the best graphics. It did not deliver the fastest performance. It did however deliver the most important thing significantly better than all of the other competing hand-held game devices at the time – it delivered the longest play time on a set of AA batteries. That differentiator enabled the Gameboy to not only outlive every other single competing device, but it has led to a long line of successive devices that enjoy large volumes in sales.

Until recently, developers were left to their own machinations to estimate and measure the energy consumption of their designs. Some silicon vendors over the years have offered device specific spread sheets to help their customers better estimate energy consumption for different operational scenarios. These types of tools require the developer to intimately understand how their system transitions between the various power saving modes. Going beyond spread sheets, in 2008, Tensilica added a graphical user interface to its Xenergy tool that helps hardware and software developers to make trade-offs that yield better energy consumption based on a cycle-accurate simulator. This year may mark an inflection point for energy estimation and measurement tools for developers.

The Energy Micro offering, called the energyAware Profiler, interfaces via USB with the company’s EFM32 Gecko development and starter kits, and it is available now as a download. The Hitex offering, called PowerScale, measures up to four different power domains in the power supply line of each domain. The tool can track current measurements from 200nA to 1A, and it is not limited to a single type of microprocessor. The IAR Systems offering is part of the Embedded WorkBench, and it is currently in beta. It samples the power supply for board because the main component of the system power consumption is the peripherals rather than the microcontroller itself.

Several companies, including Energy Micro, Hitex Development Tools, and IAR Systems, are offering, or have announced products that are planned for production support within this year, that enable developers to match energy consumption with specific lines of code in their software. These tools measure the system power consumption and enable developers to make software and system level trade-offs during the software development process. They can help with identifying when peripherals are not being actively used by the system and are powered on – burning precious energy for no useful work. The interfaces of these tools present the energy data graphically so that it is easier for a developer to spot the points of interest.

These are just three recently announced software development tools offering visibility into the dynamic energy consumption of embedded systems under operating conditions. I believe there will be more such tools announced over the next year or so as low power operation takes on even more of the design mind space. I expect that there will also be good and complementary tutorial and tips and tricks material to help developers make the most of these tools in the years to come. I will highlight these resources and how they are changing the way designers are doing low power design as they become public. If you know of similar resources that I missed, please point them out here or email me at Embedded Insights.


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