Tag: Twitter API

A Tellstick Sensor that Twitters

There are tellstick sensors measuring temperature and humidity, not with high precision but still ok if monitoring the house when being away. The sensors might be connected to a Tellstick NET from Telldus which sends all the measurement values up to the cloud (Telldus Live). However it is always a hassle to remember how to login to Telldus Live just to check the temperatures of the sensors.

It would be nice if one could read the temperature from some app already in use – twitter fits very well since it allows short text messages and it is possible to read both from an app and from a PC (no login required).

Telldus has an API to Telldus Live having the address: api.telldus.com. The API is a REST interface possible to access using GET requests and the text answers are in simple JSON format. It is definitely possible to to periodically fetch the temperature value of a sensor. Next step is to push the temperature value up to a twitter account. The twitter REST API was released as early as 2006 and have to be considered mature – see api.twitter.com. By using this API it is possible to automatically twitter status message and it might for example be used by IoT devices.

The Telldus API and the Twitter API use the standard OAuth (Open Authorization) to authorize clients. This standard is used by many companies including Facebook and Google. The standard makes it possible for service vendors to give limited access to certain parts of their API to registered clients. The registered clients might be applications, mobile apps, or back-end systems. OAuth requires you to generate 2 pair of keys, where one pair is authorization of the user or application (consumer key/consumer secret) and the other pair is authorization of the service request (access token/access secret). Once calling one of the REST API:s the public key is put directly in the HTTP authorization header and the secret key is used together with the other parameters to create a hash signature also going into the header.

If searching on pypi (the python package index), there is already a python library ‘tellive‘ for connecting to Telldus Live. The tellive library contains a client class which takes care of the constructing of the ┬áREST url and the HTTP authorization header. However you still have to know a bit of how the REST api:s work to be able to use the correct arguments. Twitter on the other hand has several independent implementations calling the REST api:s. Among them is the python-twitter which seems pythonic and stable.

Now we have everything to put together a script which uses both the libraries ‘tellive-py’ and ‘python-twitter’:

The class ‘OAuthCredentials’ contains the two key pairs (consumer and access). The function ‘get_temperature’ uses the ‘tellive’ library by listing all sensors and find the value of requested sensor. The function ‘send_to_twitter’ uses the ‘python-twitter’ library to post a string containing the temperature to the twitter account belonging to the specified customer keys. Finally decide how often the script will run and make a crontab configuration.

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