obd

obd is a ruby gem that lets you communicate with a car's OBD-II port via an adapter that supports the ELM327 command set. A great choice is the STN1110-based OBD-II UART board from sparkfun (and cable).

Usage

Simply install the gem:

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gem install obd

And you're ready to roll:

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require 'obd'

obd = OBD.connect "/dev/tty.obd"

We can send hex commands and get a response:

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obd.send("01 0C")
#=> "41 0C 26 0D"

But, that's not very useful. Fortunately, the obd gem will translate the result for us, as well as make it available with a simpler syntax:

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obd[:engine_rpm]
#=> "2435.25rpm"

You can also turn off that pesky “Check Engine” light:

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obd.send("4")
#=> "OK"

Grab the source code on github.