[nuttle]

You can also use an incremental encoder with an index to detect a fixed zero position. However, the last I knew, these did not work well when using the built-in position control of the Jaguars, if you try to use the index pin on the Jaguar's encoder input. You'll have to have a procedure for making sure the index is picked up before you can rely on this reference. For instance, it might be possible to have the students who set the robot on the field manually twist each swerve unit so it passes the index, after the robot is powered up but before it is enabled (obviously). Another option is to have the swerve units rotate for a time right after things are enabled, in order to ensure the index has been 'seen'.

Let us know if you find a absolute optical encoder that isn't expensive, the magnetic ones seem to be more manageable in this way.