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Anthony  
#1 Posted : 04 September 2019 11:31:48(UTC)
Anthony

Rank: Newbie

Groups: Registered
Joined: 08/02/2019(UTC)
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France
Location: Paris

The Internet of Things (IoT) is literally everywhere. At the 2015 Consumer Electronics Show, for example, the floor was filled with a myriad of intelligent and connected devices. In addition to ensuring that we’re always connected, some promised to make our lives easier, while others would help to keep us in shape and keep our pets safe. There’s no doubt that smart products for the IoT are already changing the way we live.

One common theme that has emerged amid IoT wearable products is the ability to take otherwise meaningless data, such as the number of steps we take in a day, and convert them into something meaningful, like the number of calories you burned during the process of taking those steps.
From a hardware system perspective, we can broadly define an IoT wearable product as having the following functions:
- Sensing of environmental or personal conditions
- The ability to collect, process, and communicate measured data
- Minimal power consumption in standby modes

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All of the products above must have some type of sensor interface. This might be a basic accelerometer to sense motion or something more sophisticated like a pulse-oximetry-based heart rate sensor. To implement such sensors in an IoT-based embedded system, developers typically have two options. The first approach is to buy a sensor chip (IC) that provides a digital output value over a serial interface like I2C/UART/SPI. This approach is simple from a design standpoint but may be expensive to implement.

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The second approach is to create a sensor interface, typically called an Analog Front End (AFE). This is an active signal conditioning circuit comprised of op amps, filters, comparators, ADCs, and other components. It can provide a voltage level output indicative of the sensor’s measured value. This approach is slightly more complex, but it is less expensive in terms of BOM cost. It also gives developers the flexibility to tune their sensor design for optimal performance, including minimizing power consumption.

Once the system has measured the sensor values, it then processes this information to make some sense out of it. This could be a conversion of a voltage value into a heartbeat measurement or the translation of changes in digital XY-coordinates into the number of steps taken. These types of calculations often require a microcontroller (MCU) and sometimes need the additional computational power of a digital signal processor (DSP). The processor not only converts sensor data into meaningful information, it can be used to add intelligence to systems, enabling the control of other system functions based on decisions made using the sensor data. Depending upon its complexity, a system like this may require additional digital controller chips or CPLDs for real-time precision control of critical hardware systems like motors, fans, or displays.

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Such systems also require a means to communicate with other nodes or a central device that may be networked, eventually reaching the Internet via a gateway. Given that many IoT products are wearable devices, wireless communication is the preferred means. Bluetooth Low Energy (BLE), also known as Bluetooth SMART, has quickly emerged as the de facto standard for wireless communications in IoT products. This is primarily due to its low-power architecture and also due to its wide proliferation via Bluetooth SMART READY products like cell phones, tablets, and laptops. BLE enables products that can easily send processed sensor information in a recognizable form to apps running on mobile phones. These phones can in turn provide this information to Web services or other devices. Embedded BLE is available in many forms, from single-chip solutions to four-chip solutions. The design complexity increases with the number of chips in your embedded system. There are other considerations, including PCB layout and antenna tuning with a balun, that need to be considered when choosing a particular wireless implementation.

The first generation of wearable products was plagued with many issues. This is typical for any new class of products that is first introduced to the market. The two most critical flaws of these initial wearable products were poor battery life and lackluster usability, and this led to low appeal for wearables for the general consumer. These products required a better look-and-feel and user interfaces that felt natural in the form factors they were used in. Capacitive touch sensing has emerged as a popular way to implement natural user interfaces that can differentiate between touches, taps, gestures, and swipes. User interfaces based on capacitive touch sensing are also more resilient, enabling waterproof products with sophisticated and sleek-looking designs. Another improvement in the next generation of wearables includes the addition of microdisplays, either LED or graphical-based, as a sign of improved appeal to consumers.

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To solve the challenge of power consumption, the next generation of IoT wearable products requires an integrated implementation. Modern ICs are highly integrated, and many are available as SoC that combine the functionality of multiple ICs into a single device offering reduced size, BOM cost, and power consumption. For example, the PSoC 4 BLE from Cypress Semiconductor is an SoC that integrates a power-efficient, 32-bit ARM Cortex-M0 CPU and a Bluetooth SMART radio with an integrated balun in a single chip. The device also features five power modes, including two ultra-low power modes called hibernate and stop mode where the chip consumes only 150 nA and 60 nA, respectively, allowing for minimal battery loss during standby modes.

This high level of efficiency of integrated SoCs is extremely useful for wearable and other IoT products, especially for more passive sensors that acquire data and use the wireless link to send data periodically, enabling the system to operate in a low-power standby mode for the remaining period to preserve battery life. The PSoC 4 BLE also combines programmable analog blocks that allow developers to create custom AFE and interface with any type of analog sensor. Other features include CapSense capacitive touch sensing for creating modern user-interfaces and programmable digital blocks for custom control and communication.

Integrated SoCs offer a single-chip approach to IoT device design. They provide all the required components to create next-gen wearable BLE products with sleek user-interfaces, multiple sensors, and long battery life. They can simplify design by, for example, including a royal-free Bluetooth 4.1 Software Stack. Their small form factor – the PSoC 4 BLE is only 3.5×3.9mm – is also much smaller than implementations that require multiple chips and external components.

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