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This is an npm module that creates Rx.JS streams of readings from the LSM303 I2C 3D compass and accelerometer module. Information on the LSM303DLHC can be found here and it is available for purchase at Adafruit.

var i2c = require("i2c-bus");
var Lsm303Driver = require("lsm303-rx").Lsm303Driver;

var options = {
    // looking at the source code, the synchronous and
    // asynchronous open functions are identical
    i2c: i2c.openSync(1)
};

lsm303 = new Lsm303Driver(options);

console.log('Reading 10 headings...');
lsm303.streamHeadings(500) // sample every 500 ms
    .take(10)
    .subscribe(
        function (heading) {
            console.log('Next: ' + heading);
        },
        function (err) {
            console.log('Error: ' + err);
        },
        function () {
            console.log('Completed');
        }
    );

Note that you need to open the i2c-bus and pass it in to the module.

• i2c (required): The object used to communicate to the PWM/servo driver.
• magOffset: Offset to be applied to the magnometer readings.
• magMin: Expected minimum values for the compass module. This is used with magMax to calculate an offset (by averaging the values). This will be ignored if magOffset is given.
• magMax: Expected maximum values for the compass module. This is used with magMin to calculate an offset (by averaging the values). This will be ignored if magOffset is given.
• debug: If truthy, debugging to the console will be enabled.

• streamHeadings(interval, forwardVector): Produces a stream of headings in degrees from North. This uses the compass and accelerometer to allow it to compensate for tilting.
  • interval: (optional) the polling interval in milliseconds for the sensor stream. The default value is 100 ms.
  • forwardVector (optional) the normalized vector that represents "forward" on the module. The default is the value for the Adafruit breakout board, which is { x: 1, y: 0, z: 0 }.
• streamAccelerometer(interval): Produces a stream of 3D accelerometer data.
  • interval: (optional) the polling interval in milliseconds for the sensor stream. The default value is 100 ms.
• streamMagnometer(interval, rawData): Produces a stream of 3D magnometer data.
  • interval: (optional) the polling interval in milliseconds for the sensor stream. The default value is 100 ms.
  • rawData: (optional) if truthy, then the raw magnometer data is returned instead of the values in Gauss. The default value is false.

This project uses the debug library for debugging. This allows you to enable debugging using environment variables or in code before constructing the Lsm303Driver object. The name of the debugging stream produced by the library is lsm303.See the debug library documentation for more information.

This project is written in TypeScript. The library can be used by plain JavaScript as shown above, and the typing information is also included with the library so that anyone wishing to use Typescript will gain the benefits of the type information.

This module was based on Pololu's Arduino library for the LSM303 module with some ideas borrowed from the lsm303 NPM module.