How to design the most energy efficient wireless sensors with ARM Cortex-M4 Wonder Gecko


rasmusRasmus is a Support & Training manager at Energy Micro, supporting customers with technical articles, seminars, and video materials. He also operates “The Lizard Lounge” forum open to everyone to share engineering ideas and application design tips.

In a series of posts on the Energy Micro blog, I´ll take a closer look at some of the features that are available for ARM Cortex-M microcontroller users. I will also show you some examples how I normally use them, and how they can be helpful when trying to reduce the energy consumption in embedded applications. 

Battery operated wireless sensors are becoming widely used in a variety of areas like home automation and industrial devices. Though these sensors are quite simple, a lot of energy is consumed in transmitting the sensor data wirelessly in a raw form to the central nodes.

With latest energy efficient microcontrollers like the ARM Cortex-M4 based EFM32 Wonder Gecko microcontroller, you can now enable more of this sensor data to be processed locally in your sensor. This helps save overall energy as less data needs to be transferred over the wireless link. The extended DSP(Digital Signal Processing) and FPU(Floating Point Unit) of the ARM Cortex-M4 allow the sensors to complete signal processing tasks much faster than a regular microcontroller. In addition, you can optimize built-in 12 bit ADC/DAC, analog comparators, operational amplifiers, and advanced sensors such as resistive, capacitive, and inductive sensors.

In regular microcontrollers, the MCU needs to wake up regularly, measuring the sensor to decide if the sensor data is interesting and further processing is needed. This approach leads to a lot of wasted energy in activating the CPU in the cases where the sensor does not show any interest. To save energy in these applications, an innovative Low Energy Sensor Interface (LESENSE) allows the Wonder Gecko to autonomously monitor the state of such sensors while the device stays in sub- µA sleep modes. By using the LESENSE, the Cortex-M4 can handle the result in detail only if programmable thresholds are exceeded.

Watch a video describing how the LESENSE works on a touch application:

Download white papers about the LESENSE with capacitive, inductive, and resistive sensors:

Smart Capacitive Touch and Gesture Detection in sub-µA Deep Sleep Mode

Efficient Metal Detection and Inductive Sensor Monitoring in sub-µA Deep Sleep Mode

Fast Wake up on Analog Events and Autonomous Rotational Tracking in sub-µA Deep Sleep Mode

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