Determinism is the ability to respond in a consistent, predictable time delay. Ethernet, even if it can be a fast network, is not determinism as collision between messages can create unpredictable delay. Of course, if the load on the network is very low or if you use Ethernet switch, it is...
93C46 from MicroChip take a wild to initialise at power up. It is not in the datasheet but you must wait a minimum of 10msec before addressing the 93C46 from MicroChip. It is usually not a big problem to wait 30msec or more at start-up to be sure that all components are all initialised...
Generally, analogue inputs have high impedance and can generally be neglected (if it is not the case, the voltage reading will be inexact). With the high price of the solar energy, you don't want to use too low impedance. If you use too high value resistors, the system will be too sensible to...
Try :
http://www.faqs.org/docs/Linux-HOWTO/Serial-Programming-HOWTO.html
For more help: www.google.com
and search <linux howto serial communication programming>
Hope it will help you.