Well I have been struggling to find a solution to my problem. I am trying to get analog output from Arduino and from what I know Arduino doesn't offer D/A converter. But PWM pins are provided as a D/A converter. But the pulses are of course not an analog voltage. So I tried to use a simple RC filter after the PWM signal and the output of the filter is connected to the A/D pin of xbee. According to theory the filter has to make the pulses as smooth as possible with certain value of the ripple. Even though I have decreased the value of the ripple, as soon as I connected the output of the filter to the Xbee, something strange happens!!! The A/D pin of Xbee starts reading multiple values. The voltage fluctuates randomly. Of course the voltage that I want is one of those multiple values, but because of my application, I cannot have multiples output voltages for same input. I really don't know the reason behind this and this is why I can't really solve the problem. I would appreciate any insight on this issue. Thanks.