Thanks to symmetric multiprocessing and higher frequencies, the computing power of wearables keeps increasing. Ever-increasing processor speed results in a rise in the number of features and subsequent memory requirements and bandwidth of the wearables. This is accompanied by reduced power consumption thanks to more energy-efficient batteries. We took a closer look at the key components.
Microcontroller - the heart of a wearable device
A microcontroller is a single-chip computer system.
The most important electronic component in wearable devices is the microcontroller unit (MCU). It integrates all key peripherals that are managed and controlled by the MCU. This includes sensors that record the outside world for the chip. To enable an accurate vital parameter analysis, data is collected via an accelerometer, motion sensor, gyroscope, optical sensor, and bioelectronic sensor. Yet it’s not just sensors that are connected to the MCU, but also vibration motors, screens and many other components. The ARM (Advanced RISC Machine) processor architecture is the most widely used MCU in the world. The ARM Cortex-M processor family offers different performance and cost options for every application. The Cortex-MO is the smallest, low power and most affordable MCU available, while the Cortex-M7 offers the highest performance and is also the most expensive processor.
More stamina through energy saving
Lithium-ion batteries are used in almost all portable devices today. These include mobile phones, laptops and smartwatches.
Most wearables use rechargeable lithium-ion batteries with a voltage of about 3.7 V. However, lower voltage is usually required to handle the power supply of wearables. Tiny step-down (buck) converters are needed to regulate down from 3.7 volts to the lower voltage. A standby mode often comes standard with wearables. It decreases the power consumption. This doesn’t just deactivate needed peripherals like a screen, for example. Standby mode also prompts the MCU to go into power save mode.
Sooner or later, the battery will drain, despite being in power-saving mode. That’s why lithium-ion batteries must be charged regularly to facilitate the continued use of the wearable device.
The battery can be charged via a universal serial bus (USB) cable. Users only need a cable, a standard wall socket plug and a power outlet. Like mobile phones, wearables also permit wireless charging but require a charging interface. Inductive coupling is one of the most commonly used methods in the industry. A transmitter coil induces a voltage wirelessly in the receiver coil that’s embedded in the wearable device.
Wearables can communicate with mobile phones, computers and clouds to exchange data. There are several ways to connect to the wearable.
USB, Bluetooth (v3 or v4.x) and WiFi 802.11 a / b / g / n / ac are among the different communication protocols for wearables. Despite the fact that USB continues to be essential for charging the wearable systems, it is losing importance as it pertains to data exchange. Wireless solutions are increasingly important due to the mobile nature of wearables. Bluetooth 4.1 and Bluetooth 3.0 modules, in particular, are used to handle the communication between smartphone and wearable device because of their low power consumption at the microampere level. WiFi can be used if power consumption is not an issue. This allows the wearable device to connect directly to the Internet and the IoT.
Non-volatile memory is a prerequisite to handle the large data volumes of wearables. It is essential to retain the data even in case of power loss. Otherwise, wearables would need to be loaded with new software every time power is lost to the memory. That's why the MCU features built-in flash memory. Today's flash memory is based on either NAND flash memory or NOR flash memory technology. Since they are expensive and require a large amount of space compared to discrete flash memories, secure digital (SD) cards are not being used.
What does the future hold for this technology?
We can expect to see important developments in all the above-mentioned areas in the future. Ever smaller electronic components will make MCUs faster and more energy-efficient. Wearables can last longer thanks to new types of batteries. Memory size for wearable devices will increase at the same price. New Bluetooth and WiFi developments will lead to even more energy-efficient communication solutions. It will be interesting to watch the trends that will shape the future of wearable technology.
Lectures during COMPAMED 2018
Learn more about wearables in these lectures at COMPAMED 2018 & MEDICA 2018: