Accel 13 Click features an ultra-low power triaxial accelerometer sensor with embedded intelligence, labeled as the IIS2DLPC. This Click board™ allows linear motion and gravitational force measurements in ranges of ±2 g, ±4 g, ±8, and ±16 g in three perpendicular axes. This smart sensor allows the Accel 13 Click to detect many different events, including tap, double tap, step counting, activity recognition (walk, run, stand still), activity change (any type of acceleration pattern change), orientation, and more. It features an onboard data processing, offering the acceleration data directly, over the standard I2C or SPI interface.
Accel 13 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.
With the total height of 0.7mm, the IIS2DLPC is well suited for using it in handheld or other space limited devices. Its powerful event detection engine is equipped with a set of features suitable for a wearable device, including free-fall, wakeup, highly configurable single/double-tap recognition, activity/inactivity, stationary/motion detection, portrait/landscape detection, and 6D/4D orientation. The sensor can use any of its two interrupt pins to report a detected event. Accel 13 Click can be used for a rapid development and testing of various applications based on step counting, fitness applications, profile switching and display ON/OFF applications, angle measurement applications, and similar applications.
Accel 13 Click is based on the IIS2DLPC, a high-performance ultra-low-power 3-axis accelerometer for industrial applications, from STMicroelectronics. This sensor has many features perfectly suited for wearables, handheld, and IoT applications, offering a good balance between the performance and the power consumption. One of its key features is its extremely low power consumption, which makes it perfectly suited for such applications. There are several power modes which the IIS2DLPC device can use. While in Low Power mode, the device consumes the least power, but the access to some features is restricted. More information can be found within the IIS2DLPC datasheet.
The IIS2DLPC sensor can measure acceleration within ranges of ±2 g, ±4 g, ±8, and ±16 g. It can output the measurement data using the Output Data Rate (ODR) from 1.6Hz (Low Power mode), up to 1600Hz (Performance mode). A high-precision analog front end facilitates highly sensitive MEMS, featuring a 14-bit A/D Converter. It allows very high accuracy of the output, even during very low amplitude changes. This makes the sensor particularly sensitive and accurate with movements that generate relatively low acceleration signals. However, using a highly sensitive MEMS makes the IIS2DLPC prone to damage caused by extremely high g-forces (10,000 g for less than 200 µs).
Acceleration data is available in 14-bit format from both the data registers and the internal FIFO buffe, which can can memorize 32 slots of X, Y and Z data. The FIFO buffer can be used for more complex calculations or timed readings, reducing the traffic on the communication interface. The interrupt engine facilitates the FIFO buffer, triggering an interrupt for two FIFO events: watermark event, and FIFO buffer full event. FIFO buffer allows optimization within the firmware that runs on the host MCU.
Besides the acceleration MEMS and complementary analog front-end circuit, the IIS2DLPC sensor also has an integrated temperature sensor. It is updated up to 25 times per second, and sampled to an 12-bit value (complement of 2’s format).
Interrupts can be triggered for many different events. Some basic events include the data-ready interrupt event and aforementioned FIFO events, while so-called feature engines can trigger an interrupt for any of the detected motion/movement events, including step detection/counter, activity recognition, tilt on wrist, tap/double tap, any/no motion, and error event interrupt. The extensive interrupt engine can use two programmable interrupt pins. Both of these pins can be assigned with any interrupt source and can be either LOW or HIGH on interrupt, depending on settings in appropriate registers. These two pins are routed to PWM and INT pin of the mikroBUS™, and are labeled as IT1 and IT2, respectively.
Accel 13 Click offers two communication interfaces. It can be used with either I2C or SPI. The onboard SMD jumpers labeled as COMM SEL allow switching between the two interfaces. Note that all the jumpers have to be positioned either I2C or to SPI position. When I2C interface is selected, an additional SMD jumper labeled as ADDR SEL becomes available, determining the least significant bit of the IIS2DLPC I2C address. The Click board™ should be interfaced only with MCUs that use logic levels of 3.3V.
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