ADXL345_WE

Arduino Library for the ADXL345 and the ADXL343 accelerometer.

I have tried to create a library for the ADXL345 which is easy to use for people who don't want to deal with all the registers. Therefore I have added lots example sketches which will enable you to deal even with the more complex features such as the FIFO modes. Howerever I still recommend to have a look into the data sheet to get a deeper understanding.

You can use both I2C and SPI. If you want to find out how to use SPI, look at the ADXL345_SPI_basic_data.ino.

ADXL343 vs. ADXL345

The ADXL343 has the same registers and settings like the ADXL345. The data sheets of both devices differ only marginally, e.g. the sensitivity of the ADXL345 has defined min./max. values, whereas the ADXL343 has only typical values. All example sketches run on both devices without any changes. However, with version 3.0.2 I have introduced a new ADXL343_WE class and defines like "ADXL343_RANGE_8G" because users might feel better using the correct name.

The ADXL343 modules that I have seen so far have two QWIIC connectors, which are convenient to use if your MCU board also has a QWIIC connector (e.g. Arduino UNO R4).

Important Note on Release 3.0.0

In versions < 3.0.0, there were several functions that returned a structure of type "xyzFloat". To be exact not the structure was returned but a pointer to this structure. Since the structures were created in the functions, the memory space where they were stored could have been overwritten. I have now changed this, but unfortunately, former sketches are not compatible anymore. However the change you need to apply is small. Example:

Version < 3.0.0:

xyzFloat g = getGValues();

Versions >= 3.0.0:

 xyzFloat g;
 myAcc.getGValues(&g);

General Information

A detailed tutorial is available:

https://wolles-elektronikkiste.de/adxl345-teil-1 (German)

https://wolles-elektronikkiste.de/en/adxl345-the-universal-accelerometer-part-1 (English)

If you are not so much experienced with the ADXL345, I recommend to work through the examples in the following order:

1. ADXL345_basic_data
2. ADXL345_SPI_basic_data
3. ADXL345_calibration
4. ADXL345_angles_orientation
5. ADXL345_pitch_roll_corrected_angles
6. ADXL345_sleep
7. ADXL345_free_fall_interrupt
8. ADXL345_data_ready_interrupt
9. ADXL345_activity_inactivity_interrupt
10. ADXL345_auto_sleep.ino
11. ADXL345_single_tap
12. ADXL345_double_tap
13. ADXL345_fifo_fifo
14. ADXL345_fifo_stream
15. ADXL345_fifo_trigger
16. ADXL345_SPI_two_devices_one_interface
17. ADXL345_SPI_two_devices_two_interfaces

To develop this library I have worked with a ADXL345 module. It should also work with the bare ADXL345 IC. For the module I have noticed that the power consumption is much higher than mentioned in the data sheet. I think the issue is the voltage converter on the module. You can reduce the power consumption by choosing 3.3 volts instead of 5 volts. At least this worked with my module.

If you like my library please give it a star. If you don't like it I would be happy to get feedback. And if you find bugs I will try to eliminate them as quickly as possible.

If SPI does not work

My library has implemented SPI 4-Wire. Some modules have SDO connected GND via an 0 ohm resistor. With this resistor only SPI 3-Wire would work. Your options are:

1. Remove the 0 ohm resistor connected to SDO (R4 on my module)
2. Replace the 0 ohm resistor connected to SDO by an internal or external pull-down resistor of 4.7 kohm or 10 kohm
3. Find another library which supports SPI 3-Wire

Another SPI issue might occur when using ESP8266 boards like the WEMOS D1 mini or NodeMCU. The standard CS Pin (e.g. D8/GPIO15 on a WEMOS D1 mini or NodeMCU) might not work since the CS Pin on most ADXL345 modules has a pull-up resistor. And if D8 is high at reset, the ESP8266 will not boot. In that case choose a different ESP8266 pin as CS!