The FreakLabs FL-ADXL345-DEV accelerometer board is a rapid prototyping sensor board designed to quickly evaluate and test applications that require an accelerometer. The board uses an ADXL345 3-axis accelerometer with a high sensitivity and +/-16g maximum measurement capability. The board also contains a FreakLabs universal serial peripheral connector so that it can be seamlessly integrated into any FreakLabs MCU development board.
The ADXL345 was chosen because of some very nice features. One of the main features is a digital interface using either I2C or SPI bus. Previous versions of the Analog Devices 3-axis accelerometer MEMS sensors had three separate analog outputs and required three ADC channels. The ADC channels are now integrated on-board the chip and the measurements for each axis can be directly read from the chosen bus.
Integrating the measurement circuitry on-board also allowed the ADXL345 to incorporate other interesting features such as two separate interrupt lines, tap and double-tap detection, activity/inactivity detection, free-fall detection, smart power management, and FIFO-buffered measurements.
I've written an open source driver for the ADXL345 which can be configured to use either the I2C or SPI bus to access the device. I've also included an open source package that integrates the driver into the FreakUSB protocol stack for the Chibi boards as an example of how the ADXL345 driver is used.
As always, schematics, layout, and BOM (bill of materials) can be found in the user guide. Enjoy :)
FL-ADXL345-DEV-v1.1 User Guide
FreakLabs ADXL345 Driver Source Code
FreakUSB + ADXL345 Demo Source Code