NXP MMA8451 3-axis Accelerometer Service plug-in for express-modular-server

This is a plug-in for express-modular-server. It provides a service which samples the NXP MMA8451 3-axis accelerator through the Linux event device for the specified amount of time.

If a string option is presented upon initialization, it is the base endpoint to serve accelerometer samples from. If this option is not present, a base endpoint of /accelerometer/ is used.

Install

npm install service-mma8451

The device you are running on must have kernel support for the mma8451. This code has been tested on a Technologic Systems TS-7680 with accelerometer option, compiling and installing support for boards shipped without it can be found here.

Usage

The following example loads the mma8451 module with the default endpoint:

var server = require("express-modular-server")({
     http:true
   })
    // other API calls here
    .API("mma8451")
    .start()

In this example, an endpoint of /acc is used to serve accelerometer samples:

var server = require("express-modular-server")({
     http:true
   })
    // other API calls here
    .API("mma8451","/acc/")
    .start()

To acquire accelerometer samples from the endpoint, pass the number of milliseconds after the trailing slash. The data is returned a text/plain which each line containing comma separated values of time (as number of milliseconds sinch the Epoch), x, y, and z-axis values as reported by the chip according to the current scale.

Example (sample accelerometer for 1 second):

wget http://192.168.1.100/accelerometer/1000

To Do

Allow for an object to be passed to options. Allow for a key in the object to specify the scale to use and the polling period.

Don't hardcode the event device file.

Copyright

Written by Michael Schmidt.

License

GPL 3.0