ADXL345 3-Axis Digital Acceleration Sensor by Bombay Electronics

Introduction The ADXL345 is a small, thin, low power, 3-axis MEMS accelerometer with high resolution (13-bit) measurement at up to +/-16 g. Digital output data is formatted as 16-bit two’s complement and is accessible through either an SPI (3- or 4-wire) or I2C digital interface.
ADXL345 Datasheet Hardware Overview Features
Supply Voltage: 2.0 - 3.6 VDCUltra Low Power: As low as 23 uA in measurement mode, 0.1uA in standby mode at 2.5VSPI or I2C Communication Single Tap / Double Tap Detection Activity / Inactivity Sensing Free-Fall Detection The ADXL345 has special sensing abilities! The single and double tap sensing detects when a single, or two simultaneous, acceleration events occur. Activity and inactivity sensing detect the presence or lack of motion. Free-fall sensing compares the acceleration on all axes with the threshold value to know if the device is falling. All thresholds levels that trigger the activity, free-fall, and single tap/double tap events are user-set levels. These functions can also be mapped to one of two interrupt output pins. An integrated, patent pending 32-level first in, first out (FIFO) buffer can be used to store data to minimize host processor intervention.
The ADXL345 is well suited to measure the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion or shock. Its high resolution (4 mg/LSB) enables measurement of inclination changes less than 1.0°. Furthermore, low power modes enable intelligent motion-based power management with threshold sensing and active acceleration measurement at extremely low power dissipation.
Applications Handsets Medical Instrumentation Gaming and Pointing Devices-industrial Instrumentation Personal Navigation DevicesHard Disk Drive (HDD) protection GND   This pin must be connected to ground VCC   Supply VoltageCS   Chip SelectINT1   Interrupt 1 OutputINT2   Interrupt 2 OutputSDO   Serial Data Output (SPI 4-Wire) / I2C Address Select SDA / SDI / SDIO Serial Data I2C / Serial Data Input (SPI 4-WIRE) / Serial Data Input and Output (SPI 3-Wire)SCL/SCLK  Serial Communications Clock