accel

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What is accel?

Accel is a simple library written in C that uses accelerometer data to find gestures in realtime. Though it is written with the Pebble in mind, it should work with other embedded devices as well.

API Overview

Return types

All methods in the accel API return a success value or error codes.

Return values are as follows:

• ACCEL_SUCCESS - the method being called is successful.
• ACCEL_PARAM_ERROR - parameters being passed are invalid.
• ACCEL_MALLOC_ERROR - returned when malloc fails
• ACCEL_NO_VALID_GESTURE - when gestures are queried, this value is returned when there are no applicable gestures.
• ACCEL_INTERNAL_ERROR - there is an internal error in the accel library, usually due to consistency issues in parameter attributes. It's best to report these.

Methods

• int accel_generate_state(accel_state **state, int dimensions, int window_size)
  • Generates and sets up a valid accel_state object that tracks input of dimensions dimensions, using a rolling window of size window_size to smooth measurements.
• int accel_destroy_state(accel_state **state)
  • Destroys any accel_state objects passed in, and resets state to point to the NULL value.
• int accel_start_record_gesture(accel_state *state, int *gesture)
  • Starts to record a gesture, saving the gesture id to gesture.
• int accel_end_record_gesture(accel_state *state, int gesture_id)
  • Completes recording the gesture at gesture id gesture_id.
• int accel_process_timer_tick(accel_state *state, int *accel_data)
  • Called whenever a tick happens, this allows accel to update projected most-likely gestures.
• int accel_find_most_likely_gesture(accel_state *state, int *gesture_id, int *distance)
  • Returns the id of the gesture that is most likely to have occurred.

Using accel in Your Project

Getting the accel Source Code

Getting the accel source is easy. Simply clone the github repository as follows:

git clone https://github.com/shalecraig/accel.git

Using accel in Pebble Projects

Simply copy all files from the accel/src directory in accel into the accel/src directory in your pebble app. The pebble build command will find the newly added files, so everything should work smoothly.

cp accel/src/* myproject/src/

A sample of library usage is in the accel/samples directory.

Using accel in Other Projects

The source code is in the accel/src directory. Simply include accel.h and make sure you compile all files. If you needed to make changes, feel free to submit pull requests to the accel repo.

Running tests

After going to the test directory (cd test/), running make run should execute tests successfully.

TODO: As of right now, C tests are compiled by the C++ compiler. We should fix this.

Current Version

The accel version is currently 1.0.0b. This version is defined in accel.h as ACCEL_VERSION_CODE , which is generated using the ACCEL_VERSION_GEN macro.

Attribution

Gesture recognition adapted from:

• Jiayang Liu, Zhen Wang, Lin Zhong, Jehan Wickramasuriya, and Venu Vasudevan, "uWave: Accelerometer-based personalized gesture recognition and its applications," in Proc. IEEE Int. Conf. Pervasive Computing and Communication (PerCom), March 2009.