ADXL345 Three Axis Acceleration Sensor
The ADXL345 Three Axis Acceleration Sensor is a thin, low power Micro Electro Mechanical System (MEMS) accelerometer module with both I2C and SPI interfaces used for tuning input shaper on your 3D printer.
Documentation on wiring your ADXL345 to the Raspberry Pi can be found here
The Datasheet for the ADXL345 can be found here
Klipper has built-in support for ADXL345 accelerometer, which can be used to measure resonance frequencies of the printer for different axes, and auto-tune input shapers to compensate for resonances. Note that using ADXL345 requires some soldering and crimping. ADXL345 can be connected to a Raspberry Pi directly, or to an SPI interface of an MCU board (it needs to be reasonably fast).
When sourcing ADXL345, be aware that there is a variety of different PCB board designs and different clones of them. Make sure that the board supports SPI mode (small number of boards appear to be hard-configured for I2C by pulling SDO to GND), and, if it is going to be connected to a 5V printer MCU, that it has a voltage regulator and a level shifter.