I’m confused by the usage of UEXT4 in the drivers for the MP3 shield. Is that pin 4 of the UEXT connector? If that’s correct, how is it connected to the MP3 shield?
My problem here is that I need a UART, and if UEXT4 is used, then I’ve lost the one on the UEXT connector; the one on the Arduino connectors is connected to the UART on the MP3 shield, so I can’t use that either.
There are 3 UARTs on domino and you can add 100 USB serial cables 
Yes, Although I do not quite understand your question this would probably be the way to go.
More details in the brochure.
You can choose for either usb-serial (RS232) or USB-TTL cables.
From reading the brochure I can move COM4 to different pins, that sounds like the way to go.
imken,
I got your question. It seems that there is a copy-paste mistake in the MP3 Shield driver.
This shield should not use UEXT4. I updated the driver for you please download it again.
This is the fix
// _reset = new OutputPort((Cpu.Pin)FEZ_Pin.Digital.UEXT4, true); //Reset pin is not connected in the this shield to any IO
Ahah! That makes sense now…