Accel to angle

This library provides functionality to convert accelerometer data into pitch and roll angles. You can use the calculated data further to check for the motion detection of the device.

Overview 

This library processes raw accelerometer data and computes rotation values based on the input. Using an accelerometer instead of a gyroscope decreases the power consumption and cost.

The library supports multiple axes and you can configure it to work with different accelerometer sensors. You can use it simultaneously or independently for rotation calculation and threshold-based motion detection.

Implementation 

The library is divided into the following two parts:

The core library that handles the conversion of accelerometer data to rotation data.
The motion detection module that uses the rotation data to determine if motion has occurred based on thresholds.

You can use both parts independently or together, depending on the application requirements.

The library also supports optional filtering of the accelerometer data before conversion. You can use the already implemented filter or create your own custom filter that is compatible with the library API.

Configuration 

To enable the library, set the CONFIG_ACCEL_TO_ANGLE Kconfig option to y in the project configuration file prj.conf.

Usage 

To use the library, perform the following steps:

(Optional) If you want to use filtering in the data conversion pipeline, you must define the filter instance. Ensure that the filter structure is always available during library usage. The contents of it must never be accessed or used directly by the application. You have the following two options to define a filter:
- Use one of the already implemented filters that are delivered together with the library. Currently, the library only supports the exponential moving average (EMA) filter. You can allocate the EMA filter instance with the help of the ACCEL_TO_ANGLE_FILTER_EMA_DEFINE macro that is available in the include/accel_to_angle/filter/ema.h header.
- Use a custom filter that is compatible with the library API. For an example on how to develop a custom filter, see the Accel to angle EMA filter.
Define and initialize the library context structure by calling the ACCEL_TO_ANGLE_CTX_DEFINE macro. The context structure must never be accessed or used directly by the application. If you want to use optional filtering step, pass the filter instance to the ACCEL_TO_ANGLE_CTX_DEFINE macro. Otherwise, you can use the NULL value.
(Optional) Reconfigure the filter with the accel_to_angle_filter_set() function to change a filter.
Fetch accelerometer data from the sensor and populate the sensor values array.
Call the accel_to_angle_calc() function to convert accelerometer data to rotation data.
Use the calculated rotation data in your application.
(Optional) Call the accel_to_angle_diff_check() function to check if the change in rotation exceeds thresholds for motion detection.
(Optional) Use the accel_to_angle_state_clean() function to reset the accumulated state of the motion difference and filter state (if used).