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ADXL355 on Raspberry Pi

Python 3 library to connect ADXL355 PMDZ accelerometer on Raspberry Pi.

Using SPI protocol, the library connects to device to read, write and obtain data from ADXL355.

Usage

To test this library on Python console:

$ python3 -i lib/adxl355.py

Then

adxl355 = ADXL355()
axes = adxl355.get_axes()
print(axes)

Settings

All the device values are stored as constants on lib/adxl355.py file. The most important are:

  • SPI_BUS: SPI bus where the accelerometer is connected
  • SPI_DEVICE: SPI id of the accelerometer

If everything is connected as the 'Wiring' section says, both device values should be 0.

Methods

  • constructor(measure_range): Initializes an ADXL355 object. A measure range can be specified as follows: 0x01 for 2G (default), 0x02 for 4G and 0x03 for 8G
  • write_data(address, value): Writes value to address
  • read_data(address): Reads ADXL355's address
  • read_multiple_data(address_list): Reads multiples addresses from ADXL355
  • get_axes(): Obtains current values for X, Y,Z

How does it work?

Requirements

  • Raspberry Pi
    • Tested on Raspberry Pi Zero W
    • Raspbian Stretch Lite installed
  • ADXL355 PMDZ

Enable SPI interface

In order to use SPI on Raspberry Pi, the interface must be enabled. On the raspberry console:

$ raspi-config

On the menu, select Interfacing Options/SPI, and then enable interface.

Wiring ADXL355 to Raspberry Pi

ADXL355 Pin Numer ADXL Pin description GPIO Pin
1 Chip Select 24
2 Master Out Slave In (MOSI) 19
3 Master In Slave Out (MISO) 21
4 Serial Clock (SCLK) 23
5 Digital Ground 25
6 Digital Power 17
7 Interrupt 1 Not Connected
8 Not Connected Not Connected
9 Interrupt 2 Not Connected
10 Data Ready Not Connected
11 Digital Ground 09
12 Digital Power 01

Install SPI Python library

To install spidev, on Raspberry Pi console:

$ sudo apt-get install python3-pip
$ pip3 install spidev

Test device

Two examples are included on this repo.

Example 1: Obtain current values of axes

To run this example (on Raspberry Pi console):

$ cd examples/
$ python3 current_axes_values.py

The output should be something like this:

{'x': 495873, 'y': 422842, 'z': 67185}

Example 2: Obtain current values of axes each 0.1 secs.

To run this example (on Raspberry Pi console):

$ cd examples/
$ python3 current_values_loop.py

The output should be something like this:

{'x': 487683, 'y': 705456, 'z': 330437}
{'x': 495886, 'y': 799674, 'z': 199731}
{'x': 438536, 'y': 881595, 'z': 462199}
{'x': 614660, 'y': 541619, 'z': 919630}
{'x': 647432, 'y': 857012, 'z': 396566}
{'x': 405775, 'y': 222158, 'z': 66401}
{'x': 495884, 'y': 197575, 'z': 787212}
{'x': 422147, 'y': 807862, 'z': 3152}
...