I would like to drive a small audio amp chip which has a simple digital volume control (or more excatly...a digital attenuator). Essentially, the spec says (http://www.nxp.com/acrobat_download/...DA8551_T_2.pdf) that to turn the volume up, the chip needs a positive pulse & to turn the volume down it needs a negative pulse...this thing is, it only uses one pin to control the volume...therefore I need find away, of having two pins on a PIC, combine into one, & with the quiescent mid point @2.5V.

When the PIC sends a positive pulse, the quiescent 2.5V goes to 5V & when the PIC sends a negative pulse, the 2.5V goes to 0V

Any ideas or schematics to hand?

Many thanks,
Hank.