> I don't have a way to debug it, or a way to connect it to serial
> custom target board
Shoot the hardware designer. Now. Unless that's you, in which this still applies.
How are you getting the code into it if you don't have a debug pod? I though that was how you programmed these things. Or is this one of the "Flash Emulation" CPUs?
Can you get to any pins that can be reprogrammed/multiplexed as a serial port? You can get 3V Serial out of that and then you wire an off-board RS-232 converter to it. You can even buy 3.3V serial level USB->RS232 pods for this purpose.
OK, so you go back to a previous era and debug by flashing a LED. How's your Morse Code? Or if you can get to any pin you can use it to bit-bang a serial stream using a software UART.
But seriously, you've got a working TCP/IP Ethernet port on that thing, so it should only take a few lines of code to connect your "printf()" statements to a basic Telnet Server. Just serve up a single port, and when connected just dump the "printf" data down it. You can connect to that using putty or "telnet ip port". If that is too hard, dump the print strings into a UDP port. You'll have to write the code to receive the data (or capture it using Wireshark).
I don't know anything about MQX. Except that for any software you want to port to anything you have to have the ability to debug it, and the higher level (source level debug pod with single-step - you know, get at least to the 1990's) the better.
Depending on which country you're in, they should have outlawed "debugging without a debugger" in 1689 or 1791. If you don't agree that it is "Cruel and Unusual", it is at least a waste of time and money that could be better spent.
http://en.wikipedia.org/wiki/Cruel_and_unusual_punishment
Tom