The Open Movement application programming interface (API) provides an interface to communicate with AX3 longitudinal movement data loggers. The devices feature a state of the art MEMS 3-axis accelerometer, flash-based on-board memory, a real time quartz clock, temperature sensor and light sensor.

The API is part of Open Movement, and is licensed under on Open Source license: the BSD 2-clause license, by Newcastle University.

The AX3 device uses a standard USB connector and enumerates on PC when connected. The device is a "composite USB device" consisting of a communications device class (CDC) and a mass storage device (MSD).
The CDC interface presents a virtual serial port for device query and configuration – the configuration software sends simple text configuration commands over this channel. The MSD interface presents a general purpose disk drive and file system, which includes the dataset file.

The API presents a consistent view of all connected devices, with set of operations for each.
This provides a common foundation for higher-level interactions, such as the Graphical User Interface.

Design Goals

The API has been designed to:

be a simple, plain C interface.
be cross-platform (targeting Windows, Mac OS, Linux).
be statically or dynamically linked to C or C++ code.
be used directly from C++, or a simple object-oriented wrapper class.
be readily used from other languages, e.g. a .NET wrapper class through p/invoke; JNI for Java.
be thread-safe, in that it anticipates being called from multiple threads, and internally handles the required mutual exclusion.
handle errors via user-checked return values (it is expected that wrapper libraries can choose raise exceptions as suitable for a language).

Requirements

The API is platform-agnostic, but parts of the implementation require some platform-specific functionality. The API currently works on Windows (XP, Vista, 7, 8, 10), Mac OS X, Linux.

The core API is written in plain C, and is easily wrapped by C++ (i.e. by an object-oriented class), or, as it can be built as a DLL with undecorated exports, other languages such as .NET (through p/invoke of the DLL). Wrappers also exist for Java and Node.js.

See also: Getting Started with the API