input negative values

my input is pulse from -0.5 - 0.5 volts .the arduino reads only possitive values . what can i do ?and the output it will a pwm signa; .any idea ??

Are you saying the input can be positive or negative, or, the the signal changes from negative to positive and back?

Are you trying to read a square wave that changes +&- or maybe analogue?

Please fully explain the signal requiring detection.

Weedpharma

My signal changes from negative to positive and back.yes its anagole and square. from -0.5 - o.5 volt.afterwards i want to do pwm and coding negative values

Maybe a LM339 comparator would be a good interface chip to the Arduino.