Accelerometer

An accelerometer senses gravity and acceleration using microscopic mechanical parts that are integrated on a silicon chip. It can be used to detect orientation, motion, and gestures like tapping.

The LIS3DH is a low-cost model of accelerometer among many others by different manufacturers. It is a digital device that talks to the microcontroller bidirectionally using a protocol named I²C (Inter Integrated Circuit). I²C uses two signal lines, SDA (serial data) and SCL (serial clock), plus a common ground. Additionally, I²C requires two resistors (pull-up resistors) between each of the signal lines and the positive supply voltage (VCC), this is already done on our LIS3DH breakout board. Multiple devices can be connected to the same I²C bus, the microcontroller can identify them by their address.

To avoid having to remember the raw commands that the microcontroller needs to send over I²C to talk to the accelerometer (they are documented in the data sheet of the part), we use a library that encapsulates that knowledge and abstracts away the specifics of the device. Check the documentation at https://learn.adafruit.com/adafruit-lis3dh-triple-axis-accelerometer-breakout and https://circuitpython.readthedocs.io/projects/lis3dh to learn more about its capabilities, such as tap and double-tap detection. Some of them require additional wiring.

Libraries required: https://github.com/adafruit/Adafruit_CircuitPython_LIS3DH and https://github.com/adafruit/Adafruit_CircuitPython_BusDevice

>>> import board
>>> import adafruit_lis3dh
>>> a = adafruit_lis3dh.LIS3DH_I2C(board.I2C(), address=0x1d)
>>> a.acceleration
acceleration(x=-0.0862066, y=0.019157, z=9.73177)
# in m/s^2

>>> import pew
>>> import math
>>> pew.init()
>>> screen = pew.Pix()
>>> while True:
...     x, y, z = a.acceleration
...     screen.box(0)
...     screen.pixel(4 + math.floor(0.3*x), 3 - math.floor(0.3*y), 3)
...     pew.show(screen)
...