Hi; I want to connect magnetic encoder AS5145 to Arduino Uno 3. I want to know which pins go where in Uno 3. Please read the datasheet attached and help me,

 

The answer to that question is not simple. The device you're attempting to explore offers several data streams: serial, pwm or 'proportional duty cycle', and analog. Further, this device presents some mechanical problems for mounting it in optimum position of the exciting magnet while being able to rotate that magnet in response to the mechanical stimulus to be monitored.

Suggest you look at a pre-packaged version of this device offered by US Digital

http://usdigital.com/products/ma3

These are very reasonably priced in low quantity, mechanically robust and already set up to provide one of two data streams . . . either PWM or analog. I'll suggest that you begin with an analog output version and use any of the analog-input pins to your target micro-controller.

I've worked with the bare chips. The $time$ and tools necessary to apply them to a task is significant. I would not recommend them to the neophyte experimenter.