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?