Share pins for audio input + UART

[jrs45]

I'm designing an audio amp (w/DSP) with a few input pins (stereo balanced) and thought it would be handy to use a couple of these pins for UART I/O as well, mostly for factory testing, maybe for customer use.  I don't want to add another socket or anything.

Is there a clean way to do this?

The audio goes through a standard RF filter/TVS/DC block into a codec (320AIC3204).  The UART would go through an RC filter + protection diodes for microcontroller pin protection, then to the microcontroller. 

In software, I can set the microcontroller pins to input of course, but I have to worry about the loading effects of this RC network and protection diodes or imposing noise on the audio signal.  Maybe it will be OK?

I'd rather avoid adding a switch for this. 

Is there a "standard" way of doing this sort of thing?