For wearable technology, the wrist is the most in demand, while other parts of the body are likely to have a lot of demand as well. Even the clothes we wear are becoming part of the next big change; technology is becoming more and more mobile as the concept of wearable technology is embraced by everyone. As an emerging industry, it relies on many technologies, but the most inseparable is the integration of electronic components. Fortunately for developers, embedded electronics is already arguably the most mature area of wearable technology, and as such offers many opportunities for OEMs to influence this emerging trend.
Wearable technology is expected to cover the fields of electronic component manufacturing, biological, biochemical and renewable energy, and is developing in an unprecedented way. It brings immeasurable opportunities for innovation, which will be active in the market for decades, and will be further extended and integrated into all aspects of modern life. We have taken tentative first steps in a process that could permanently change modern life.
Key Features
The simple pocket watch appeared as early as the 16th century, and it did not change much until the First World War. The main change was that it was moved to the wrist for convenience. This can be seen as the first ever example of "wearable technology", and for the next full century, it was basically just a means of timekeeping. Of course, the basic function of a watch has changed dramatically since the advent of integrated electronics, so it's a logical target for the first modern instances of wearables to be retrofitted.
Market analysis magazine IHS Electronics & Media defines this category of devices as being worn for an extended period of time, resulting in a vastly improved user experience, along with advanced circuitry, wireless connectivity and independent processing power. The magazine further defines wearable technology categories: fitness, medical care, industrial, military and entertainment. Broadly speaking, each of these five categories consists of different forms of data acquisition, processing, and display technologies, duplicating local processing power needs.
Of course, on a more technical level, for any device designed to be worn for extended periods of time at various levels of activity, the key attributes would be size and power consumption, both of which are as small as possible. These are requirements that integrated device manufacturers have examined for many years, and are constrained by Moore's Law and the development of manufacturing and packaging technologies. The challenge now is how to integrate advanced semiconductor technology with emerging "smart" solutions in textiles, sensors and energy. Every aspect of wearable technology relies on an optimal mix of point solutions. Fortunately, a variety of microcontrollers are already available in volume, effectively addressing the needs of this emerging industry.
leading solutions
With the introduction of the Cortex-M0+ core by ARM with leading partner Freescale Semiconductor, numerous IDMs (Integrated Device Manufacturers) have adopted this core in their ultra-low-power products. The Cortex-M0+ combines several features with low-power operation to perfectly suit a variety of application needs, and when implemented in the latest space-saving packages, it represents a solution that enables wearable technology.
For example, the Kinetis KL02 is from Freescale Semiconductor and is available in a 20-pin WLCSP (Wafer Level Chip Scale Package) package option, measuring only 2 mm on each side and less than 0.6 mm in height. In addition to being the smallest MCU offered by ARM, the KL02 features nine low-power modes, each with a unique 80-bit identification number.
Unique features help differentiate devices based on general-purpose processor cores, such as the Cortex-M0+. For example, the LPC81XM from NXP Semiconductor has a pin interrupt/pattern match engine (Figure 1) that allows levels on defined I/Os to be fetched using predefined Boolean expressions to generate interrupts. This can be useful for applications that require the processor to spend more cycles in sleep mode, as it saves battery power.
Figure 1: NXP's LPC81 family employs a pattern-matching engine to reduce CPU activity.
The Zero Gecko series, from Silicon Labs, integrates similar features in a peripheral reflex system, but is more complex. The peripherals are able to communicate with each other while the core remains in a low-power sleep mode. Gecko devices also feature Low Power Sensor Interface (LESENSE) technology, which enables the device to control up to sixteen analog sensors without CPU intervention (Figure 2). It operates in 900 nA sleep mode and can interface with capacitive, inductive and resistive sensors. This could be particularly relevant for wearable technologies developed for health monitoring or home care, where sensors will be used to monitor physical conditions over time.
Figure 2: The LESENSE interface in Gecko devices from Silicon Labs enables peripherals to interact with module peripherals without using the CPU.
As an emerging market, the term "typical" cannot be used for any wearable technology, but since it is obviously only active when worn, it is reasonable to expect any device to be inactive most of the time. But since any user expects the device to always be running "instantly" when needed, taking the time to recharge a depleted battery is never acceptable. For this reason, ultra-low-power modes are critical to ensure that the device remains ready at all times, and the Cortex-M0+ cores are designed for this low-power requirement, and IDMs can often use them to achieve overall low-power consumption strategy. Finally, a word on the STM32L0 series from STMicroelectronics, which offers a standby mode that consumes only 0.27 μA when the real-time clock (RTC) is off (the consumption rises to 0.65 μA (at 1.8 V) if the RTC is kept on). The device takes only 60 μS to wake up from standby mode, but only retains the data held in the standby registers.
Although offering only two low-power modes, the Cortex-M0+ based ATSAMD20 series from Atmel also implements an intelligent peripheral approach that minimizes core activity. The event system allows peripherals to send and receive signals (events) directly without waking up the core to execute. It works in both asynchronous and synchronous modes. The event system provides eight configurable channels, and consists of fifty-nine event "generators" and fourteen event "users" (Figure 3).
Figure 3: Atmel Event System technology allows the ATSAMD20 to remain in a low power operating mode.
energy harvesting
An unresolved problem in wearable technology is providing the device with the energy it needs (albeit a small one). Batteries are still the main solution, but batteries are relatively large, so we inevitably require or want to use sustainable sources to power smaller devices. Therefore, the concept of energy harvesting quickly became popular.
Wearable technology is developing rapidly, and it is expected that there will be huge growth potential in the field of innovation. So it is very likely that it will change our lives forever.