External I/O (Smartstream, etc.).

[webmasterpdx]

I wasn't planning on doing any measurement. I just wanted a way to communicate from a program on the prime to an external device. Then I can do anything I want.

However, your talk about probes, etc... Most of the analog measurement I've worked with in the past involved the use of ADC's and fixed connections (like monitoring some parameter (voltage or current usually). There is a standard 4mA interface that you can attach things like thermometers and other measurement "probes" that are usually fine as long as you follow the specs.
I've used the ADC's in the microcontrollers and they worked fine.

However, you need to calibrate your boards during your manufacturing process usually.

Sure, if you are desiging some kind of generic datalogger that takes multiple probes for measuring multiple parameters, then trying to be all things to all parameters will be difficult.
It's usually better to dedicate certain pins to certain parameters and to mux the ADC and use dedicated lines for certain "probes".