I have a circuit design that deals with audio. The audio circuitry is controlled with a Propeller. That stuff is working quite well so far.
I have added into the design a header to the board in order to incorporate a Raspberry Pi controller to the mix. I.E., there is bidirectional communication between the Prop and the RPi.
Once I have hooked everything together, the audio signal is seriously affected by digital noise coming from the Raspberry Pi. Quite noticeable buzzing and hissing happens whenever the Raspberry Pi is connected and powered up. I've tried simple things like adding 100uF caps to all power rails (The Audio circuitry is run at +/- 15V and the Raspberry Pi is on a +5V rail) but it hasn't even reduced the level of the noise.
Has anyone had any experience with these types of issues and could give me some steps in the right direction for getting rid of the noise? Let me know if any other info would be helpful, as in schematics, pictures, audio samples and what not.
Thanks a bunch,