[Jizvonius]

What would you be attempting to do with this robot?

If you use a computer (laptop or desktop) for the processing and control, I would hope that it would be relatively calculation/memory intensive. (ie. autonomous nav using image processing) Otherwise the system will be very overpowered in the processing/memory department.

The only low level programming that would really have to be done is to output the control signal's for your actuators. This would reqired motor drivers which can use anything from a pwm signal to a binary number to pass values to control your actuators. As far as I know, computers do not put out pwm signals by themselves so if you were to go that route, external circuitry would be required in addition to the motor drivers. If your motor drivers were to use a pin based x-bit (x is variable) signal, they would be able to take sets of pin values from your serial port to control the motors. Either option is viable and actually just changes the clocks for your motor controllers to either a central one or separate ones.

All more complex calculations could actually use a higher level software package such as MATLab, which if I remember correctly has a serial output function of its own.

(and yes motor power supplies etc. need to be isolated from the comp which is generaly the case with good, high current motor drivers anyway)

Disclaimer: any errors in this post may be attributed to me being an ME major and not fully understanding the intricacies of magic smoke.