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1. General Smart Sensor Hub Overview ?
The Smart Sensor Hub, also known as Sensor hub, is a combination of hardware and software solution based on a low-power MCU and a lightweight RTOS operating system, whose main function is to connect and process data from various sensor devices. Its main function is to connect and process data from various sensor devices. At the beginning, it was mainly designed to solve the problem of power consumption in mobile devices. Now with the increasing business, its function and performance are constantly iterated and updated.
1.1 Physical Sensors ?
In embedded mobile devices, such as smartphones, smart wearable, home medical devices and some other smart hardware devices, the physical sensors used are generally MEMS sensors, i.e., Microelectro Mechanical System (Microelectro Mechanical System) sensors. After decades of development, it has become one of the most important technologies in the world, and also involves the fields of electronics, mechanics, physics and other disciplines. Compared with traditional sensors, MEMS sensors are smaller in size, lighter in weight, lower in cost, lower in power consumption, higher in reliability, easier to integrate and develop, and other advantages. At present, MEMS sensors are mainly accelerometer (Accelerometer), magnetometer (Magnetometer), gyroscope (Gyroscope), light sensor (Ambient light sensor), close to the light (Proximity), barometer (Barometer/pressure). Humidity meter (Humidometer) and so on, according to the type can be divided into environmental sensors, sports sensors, health sensors.
1.1.1 Acceleration sensors ?
Accelerometer (Accelerometer), also known as gravity sensor, is able to sense the acceleration in any direction (gravity acceleration is only the vertical acceleration of the ground surface), accelerometer through the measurement of the component in a certain axial force to get the results, expressed in the form of axial acceleration magnitude and direction (X, Y, Z). The principle is based on the vibrating structure inside the sensor, which measures the acceleration of the object due to the external acceleration that affects the vibration characteristics of the internal structure. There are many uses for accelerometers, almost all of which are related to the movement of smart hardware (such as cell phones) (pedometer, attitude measurement of cell phones, related games, etc.).
1.1.2 Gyroscope sensors ?
With a gyroscope, there is a three-axis gyro inside the sensor. The working principle of the gyroscope is through the measurement of three-dimensional coordinate system within the vertical axis of the gyro rotor and the angle between the device, and then to calculate the angular velocity, so that you can by the angle and angular velocity to discern the object's state of motion in three-dimensional space. The use of gyroscope is also very much, such as digital photo anti-shake, as well as with the accelerometer (some have magnetic sensors or GPS, etc.) to form a fusion sensor to complete more advanced functions (such as inertial navigation).
1.1.3 Magnetometer sensors ?
A magnetometer, also known as a geomagnetometer or magnetic sensor, can be used to test the strength and direction of a magnetic field. The principle of a magnetometer is similar to that of a compass, which measures the angle between the current device and the four directions of southeast, northwest, and north.
1.1.4 Ambient Light Sensor ?
An ambient light sensor senses the intensity of the surrounding light. For example, in mobile applications such as cell phones, laptops, tablets, etc., it can be used to realize automatic adjustment of backlight brightness, etc., based on the brightness of the outside world, thus reducing the power consumption of the product.
1.1.5 Proximity Light Sensor ?
The proximity light sensor is used to detect infrared signals, and it mainly detects signals from an external infrared LED. This LED emits infrared light outwards and when an object approaches the top of the sensor, it enters the infrared emission region and some of the infrared light is emitted back to the sensor. Now there are also laser-based proximity light sensors, such as ToF sensor, etc., which can measure the range of about 2-4 meters.
1.1.6 Barometer Sensor ?
Barometer is mainly a vacuum box type barometric pressure sensor, relying on air pressure to cause deformation of the vacuum box, the upper and lower two capacitive plate distance change, capacitance change to measure the value of atmospheric pressure.
1.1.7 Hygrometer sensor ?
The main principle is the temperature and humidity in the air through a certain detection device, after measuring the temperature and humidity, according to a certain law transformed into an electrical signal or other required forms of information output, so as to detect the temperature value at that time.
1.1.8 Ultraviolet sensor ?
Ultraviolet sensors (UV) are sensors that utilize a photosensitive element to convert ultraviolet signals into electrical signals.
1.1.9 PM2.5 Sensor ?
The PM2.5 laser sensor is a general-purpose fine particle concentration sensor that uses the principle of laser scattering. That is to make the laser irradiation in the air on the suspended particles to produce scattering, at the same time in a particular angle with a detector to receive the scattered light, the photoelectric flow generated by the amplification, get the electrical signal and the corresponding curve of the particles, after a series of algorithms to derive the mass of particles of different sizes in the unit volume. The PM2.5 sensor is mainly used for embedding all kinds of fine particle concentration related instruments and meters, environmental improvement equipment, such as air purifiers.
1.2 Smart sensor hardware framework ?
According to different terminal equipment and business scenario requirements, the current sensor hardware framework can be mainly categorized into three types, MCU built-in type, MCU external type and MCU independent type. The hardware components are mainly low-power MCUs, such as ARM7, ARM9 and cortex M series, and the peripherals are mainly MEMS sensors, such as acceleration, gyroscope and so on.
1.2.1 MCU built-in type ?
Currently there are such hardware solutions mainly in smartphones, running Android or IOS on the SOC and a lightweight RTOS on the MCU. ?
1.2.2 MCU external type ?
Before there was a built-in type of hardware architecture, many smart devices on the market were based on such hardware solutions. Of course, there is still a large market for such a hardware solution.?
1.2.3 MCU-independent ?
This hardware solution is mainly used for various smart hardware devices, such as smart bracelets, sweeping robots and so on.
1.3 Smart Sensor Software Framework ?
This chapter mainly introduces the software part of the smart sensor, which will also be called sensorhub after this. it mainly involves the outline design of the general software program and the functional responsibilities of each module, including the function module, management module, driver module, etc. ?
The generic software components, as shown in the figure above, have two main parts: sensor framework and BSP. By module, it can be divided into the following modules:?
◆ Service Manager: Responsible for managing the registration and configuration of various sensor-related algorithms, such as the management of pedometers.?
◆ Device Manager: Responsible for driver management, power management, and configuration management of physical sensors.
◆ Sensor Service: Algorithms for various applications based on physical sensor data, such as pedometers, indoor navigation, and so on.
◆ Sensor Driver: Mainly refers to the physical sensor driver, some also include axial mapping, static calibration and other functions.
1.4 Sensor Data Types ?
There are two main types of sensor data: physical sensor data and algorithmically derived data based on physical sensor data, which can be referred to as virtual data or software data.
1.5 Generalized business based on smart sensor framework ?
With the arrival of the IoT Internet of Things era, various smart hardware devices increasingly rely on various sensors to realize a variety of intelligent businesses. From the popularity of personal consumer products, to today's smart home, smart city, smart industry, etc. all rely on sensors to realize their intelligence. Sensing, connecting, applying, from the analog world to the digital world, connecting the bridge cornerstone is the sensor.