Power saving has always been an important research direction in the field of microcontrollers. Dozens of low power technologies have been proposed to achieve the goal of reducing their power consumption. However, most of them focus mostly on lowering the consumption rate. It is well known that energy is the integral of power over time. Thus, our view is that both power and time should be carefully considered to achieve better energy efficiency. We reviewed some commonly used low power technologies and proposed our assumptions and strategy for improving energy efficiency. A series of test sets are designed to validate our hypotheses for improving energy efficiency. The experimental results suggest that time has no less impact on energy consumption than power. To support the operation of the processor, some peripheral components consume a constant amount of power regardless of the clock frequency, but the power consumption will be reduced when the processor enters low-power modes. This results in some interesting phenomena that are different from the usual thinking that energy can be saved by increasing processor clock frequency. For STM32F407 and Xtensa LX6 processors, this article also analyzes and calculates the minimum sleep time required for achieving energy saving based on our analytical models. Our energy efficiency strategy has been verified, and in some cases, it can indeed improve energy efficiency. We also proposed some suggestions on hardware design and software development for better energy efficiency.

Energy consumption is a critical evaluation index of embedded systems, and it has impacts on battery-life, thermal design, as well as device security and reliability. Since energy is the time integral of power, power consumption should be considered, along with the impact of “time”; thus, we propose two designs of automatic energy consumption measuring platforms utilizing General Purpose Input/Output (GPIO). Using these designs, we developed software and introduced auxiliary hardware for solutions with better timing and synchronization. A series of test sets were designed to verify our designs’ capabilities and accuracy levels. Both of our designs showed an accuracy similar to that of traditional measuring methods, which can satisfy the needs of different occasions. In addition, our designs provide real-time energy consumption data, as well as unattended automated measurements.

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In this paper, a simplified design of automatic energy consumption measuring platform for embedded systems is proposed. A straightforward device named USB-TTL replaces the intermediate device in the original design and becomes the link between the host computer and the target board. The simplification makes the design of host computer software simpler and the whole platform more reliable. It also eliminates the need to design software for the intermediate device. In general, it has features similar to the original design. A series of test sets are also designed to verify its capabilities and accuracy. Compared to the original design, the simplified one has almost consistent accuracy, is easier to deploy, and requires less wiring and devices.

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