11. Detection Algorithms Acceleration Measurement Orientation Detection Tap Detection Shake Detection Freefall/Motion Detection Tumble Detection Auto Sleep Detection Auto Wakeup Detection Standby Mode Transition to Active Mode Interrupt with output available Detect all 6 orientation positions Interrupts during 0g detection and interrupts during a tumbling event Interrupts main processor to wakeup on predetermined motion detection Interrupts main processor to go into sleep mode
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Welcome to the training module on 3-axis Xtrinsic Acceleration Sensors.
This training module will introduce Xtrinsic Sensing technology and MMA8450Q acceleration sensor.
Freescale’s Xtrinsic sensors go far beyond a sensor translating a signal—it’s enabling greater levels of sensing context and intelligence. By increasing levels of modular integration with multiple sensor inputs, logic and other building blocks, Freescale brings greater value and decision making to the overall sensing solution. Multiple sensor inputs are leveraged within the platform to perform multiple application functions. The Xtrinsic sensors feature customizable software that extends sensor use cases through algorithms and analysis to reduce complexity and provide processing assistance.
Micro-electromechanical systems (MEMS) based sensors are manufactured by building very small electrical and mechanical components on a single chip. MEMS-based sensors are crucial components in automotive electronics, health care monitoring equipment, consumer portable and wireless electronics, appliance and industrial applications. MEMS technology provides the advantages, including cost efficiency, low power, miniaturization, high performance, and improved integration. In MEMS technology, different functionalities can be integrated to reduce the component count and lower overall costs. There are two types of integrated microsystems: monolithic integration and system-in-a-package (SiP). Monolithic integration is when the MEMS device and the integrated circuit (IC) are incorporated onto the same piece of silicon. SiP is when the MEMS device and the IC are integrated into the same package.
Accelerometers are designed to detect changes in force resulting from fall, tilt, motion, positioning, shock and vibration. Freescale has created three ranges of accelerometers to detect these changes: low g (less than 20 g), medium g (between 20 g to 100 g) and high g (100 g to 500 g). For consumer electronics that require a fast response time, high sensitivity, low current consumption, low-voltage operation and a standby mode in a small profile package, Freescale’s accelerometers are an ideal solution.
The MMA8450Q accelerometer is an intelligent low power and noise, 3 x 3 x 1 mm capacitive micromachined accelerometer featuring 12 bits of resolution. This accelerometer is packed with many flexible user programmable embedded functions that are available with two configurable interrupt pins. MMA8450Q has user selectable full scales of ±2g/±4g/±8g and it is capable of measuring accelerations with an Output Data Rate (ODR) of 400 Hz, 200 Hz, 100 Hz, 50 Hz, 12.5 Hz, and 1.563 Hz. These output data rates correspond to sample intervals from 2.5 ms to 640 ms
The MMA8450Q accelerometer is designed for next-generation mobile devices, such as smartphones and smartbooks, which require an ideal blend of performance, portability and battery life to satisfy market requirements. Target applications for the MMA8450Q accelerometer include portable consumer devices such as mobile phones and remote controls, as well as smartbooks, eReaders, netbooks, laptop PCs, PMPs and PDAs. Additional applications include activity monitoring for medical applications, dead-reckoning assistance for navigation applications, position detection for fleet tracking and safety shutoff for power tools and small appliances.
The device offers a broad range of embedded and highly configurable functions designed to help designers address specific product requirements, including orientation, tap, double tap, jolt, freefall and shake detection capabilities. Using the FIFO buffer along with the embedded functions can allow the end processor to analyze only the required data, while at the same time helping to protect from the possibility of data loss when multiplexing other sensors on the same I2C bus. Configurable power saving modes and auto-wake/sleep capability help designers achieve optimal current consumption. The extensive configurability for each of the embedded functions that can be tied to the auto-wake/sleep function can enable context-aware products for more power efficiency.
Accelerometers are commonly used in hand held electronics and/or battery operated electronic devices. Consumption of current in the entire system is a critical feature of the product design. The MMA8450Q is designed to optimize energy-efficient performance. When there is a need for low power over high resolution the MMA8450Q is capable of reducing the current consumption of the part at all ODRs resulting in significant overall system power savings. The embedded functions allow the system MCU or processor to go to sleep and wait for an interrupt from the accelerometer. The FIFO has tremendous power savings potential for applications requiring data-logging or when waiting for an event to view the exact data that triggered the event. The MMA8450Q can be used to cycle between different ODRs, which results in overall lower current consumption of the device.
Here is the block diagram of the MMA8450Q accelerometer. The complete device includes a sensing element and an IC interface able to take the information from the sensing element and to provide a signal to the external world through an I2C serial interface. The embedded DSP functions increases the intelligence such as orientation, tap, double tap, jolt, freefall and shake detection. Utilizing the embedded functions in the MMA8450Q, customers can develop more robust applications such as position detection, 3-D gesture detection, pedometry and many other next-generation motion detection functions.
The MMA8450Q can be configured to generate other interrupt signals accordingly to the programmable embedded functions of the device for Motion, Freefall, Transient, Orientation, and Tap. These interrupt sources can be routed to one of two interrupt pins. The detection of “Freefall” involves the monitoring of the X, Y, and Z axes for the condition where the acceleration magnitude is below a user specified threshold for a user definable amount of time. Motion is often used to simply alert the main processor that the device is currently in use. When the acceleration exceeds a set threshold the motion interrupt is asserted. Functions such as tap, flick, shake and step counting are based on the analysis of the change in the acceleration. It is simpler to interpret these functions dependent on dynamic acceleration data when the static component has been removed. The MMA8450Q is able to detect all 6 orientations including portrait/landscape with a large amount of configuration available to provide extreme flexibility to the system designer.
The LFSTBEB8450 provides is an evaluation board for the Freescale MMA8450Q 3-axis high performance, high functionality low-g accelerometer. The LFSTBEB8450 includes an 8-bit MC9S08QE8CWL MCU for data acquisition, and an EEPROM for data storage. For customers already familiar with the Sensor Toolbox Platform, the LFSTBEB8450 is designed to work with the LFSTBBAT9 for power or LFSTBUSB for communication to a PC.
Here is the summary table. The MMA8450Q features low power digital capability, embedded functions, and g-cell / sensing cell.
Thank you for taking the time to view this presentation on “ 3-axis Xtrinsic Acceleration Sensors” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the Freescale site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit element14 e-community to post your questions.