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mySmartGrid JSONP Interface

This page specifies the JSONP interface that makes it possible for JavaScript clients from other Web domains to query sensor measurements from mySmartGrid.

Below, we describe how the interface can be used to plot measurements on a chart using the Dygraphs library. You can see the example we are building here.

How to Use

The first step is to load the Dygraphs libraries, as follows.

<script type="text/javascript"
<script type="text/javascript"
<script type="text/javascript" 

Then, you need to declare the following <script> tag in your HTML page.

<script type="text/javascript" 

The response for the HTTP request performed by this <script> tag contains JavaScript functions that return pairs of timestamps and values formatted as JSON arrays, as seen below.

function getDemoData(){
  return [[1375800420,309.0909090924],[1375800480,310.90909091040004],[1375800540,303.75]];

The URL informed in the src attribute of the <script> tag must have the following structure:<sensor id>?<parameters>

You can discover the id of your sensor by visiting the sensors page.

The table below informs which parameters can be informed in the URL.

Parameter Description Possible Values Note
unit The unit in which the measurement results will be shown Watt, kWh, Wh Optional, default: Watt
resolution The resolution of the measurement results. minute, 15min, hour, day, week Optional, default: minute
start First timestamp of the query period. Unix timestamp Required if end is also informed.
end First timestamp of the query period. Unix timestamp Required if start is also informed.
interval An alternative way of representing a standard period of time that ends right now, for example: the past 1 hour (60 min). hour, day, week Required only if start and end are not informed. Default: hour
token The sensor authentication token. Please visit the sensors page Required if your website domain is not authorized to query the sensor measurements. See security considerations below.
data_function The name of the JavaScript function that your code will be able to call in order to get the measurements. A JavaScript function name. Optional, default: get<sensor id>
callback_function The name of the JavaScript function from your code that will be called, passing the measurements array as argument. A JavaScript function name. Optional

Now, the data can be used in your page. Please, create a <div>, where the chart will be placed.

<div id="chartDiv" style="width:400px; height:200px;"></div>

Finally, create the Dygraph object in another <script> tag:

<script type="text/javascript">
  new Dygraph(
    // chart div
    // demo sensor measurements
    // chart format
      fillGraph: true,
      fillAlpha: 0.15,
      xAxisLabelWidth: 100,
      xAxisLabelFormatter: function(ms) { return (new Date(ms * 1000)).toLocaleTimeString(); },
      xValueFormatter: function(ms) { return (new Date(ms * 1000)).toLocaleTimeString(); },
      xTicker: Dygraph.dateTicker,
      xPixelsPerLabel: 100

Click here to see the result in a new page.

Security Considerations

The token grants you access to the sensor. Everyone who knows the token can also query your sensor values, so you must protect it. As you can see above, our API only works via HTTPS. In order to protect the token you should not expose it to others, i.e. by embedding the JavaScript from above in unencrypted HTML pages of your application.

If you do not want to expose the token to the user, please go to the sensors page, edit the sensor, and enter your website domain in the list of domains authorized to query the sensor. After that, mySmartGrid will authorize any query originated from a page loaded from your domain, so that you can omit the token argument from the HTTP request. Click here to see an example.

At the moment, this feature is available only for some users. If you want to use it, please send an email to

jsonpinterface.txt · Last modified: 2013/09/25 15:24 by mysmartgrid