shielding the serial cable

[Al Skierkiewicz]

Guys,
Twisted pairs minimize noise only when the receiver takes the signal differentially from both wires. This method makes the signal opposite in polarity (phase) on each wire at the transmitter while the noise is in polarity (phase) on each wire. For short distances on single ended wiring (RS232), twisting has no effect on noise pickup. If you think about it, the induced noise must exceed the trigger threshold in the receiver to be an issue. It is for this reason that RS232 implementations can use relatively high voltage for signaling. (Up to +/- 15 volts.)
The CAN buss is a balanced or differential pair so noise immunity is pretty high on those connections. The receivers are also Schmidt Trigger inputs. Shielding may help if wired as Alan has pointed out above. There is no ground on the robot but the common point for noise picked up by the shield is returned to the Crio chassis and then to the negative lead of the battery.