i have successfully analogRead a Eurorack synthesizer that outputs a 0-5V. But when i have to deal with negative values i cannot read them.
So the question is how to analogRead (and in the future) analogWrite negative values -5 to 0 Volts with Arduino? I have read about Op-Amps, or voltage dividers but i was confused more..
Negative voltages will damage the Arduino pins, don't expose them to that. You need to shift the voltage from -5.0V...+5.0V to 0.0V...5.0V, or whatever your input voltage is. You must become un-confused about voltage dividers and op-amps to do this.
The question for me is, why do you want to do this? Arduino's analog inputs are not fast enough to capture audio frequencies except with a very poor quality. So what is your project?
PaulRB explained about inputs but not about outputs. Because analogWrite(...) on most Arduinos results in a 0 to 5 volt PWM signal, using this is going to be challenging unless you are willing to do something similar to putting a DAC on the SPI or I2C bus. Of course, you could choose to use one of the Arduinos that have a true DAC output but you would still have to convert from 0 to 5 volts -to- -5 to 0 volts.