[Al Skierkiewicz]

Both of these seem to dominate the answer...
<R50> Connections to the cRIO-FRC Ethernet ports must be compliant with the following parameters:
A. The DAP-1522 radio is connected to the cRIO-FRC Ethernet port 1 (either directly or via a CAT5 Ethernet pigtail).
B. Ethernet-connected COTS devices or custom circuits may connect to either cRIO-FRC Ethernet port; however, these devices may not transmit or receive UDP packets using ports 1100-1200 except for ports 1130 and 1140.

And...
<R62> All outputs from sensors, custom circuits and additional electronics shall connect to only the following:
A. other custom circuits, or
B. additional COTS electronics, or
C. input ports on the Digital Sidecar, or
D. input ports on the Analog Breakout, or
E. the RS-232 DB-9 RS-232 port on the cRIO-FRC, or
F. the Ethernet network connected to either Port 1 or Port 2 of the cRIO-FRC, or
G. the CAN-bus if and only if all Jaguar speed controllers on the CAN-bus are wired in full compliance with Rule <R58> and Rule <R59>, or
H. the sensor inputs on the Jaguar speed controller

Custom circuits and additional electronics are allowed to utilize the Port 2 Ethernet bus and/or the CAN-bus to communicate between devices. Note however, that the ROBOT must be controlled by the cRIO-FRC (see Rule <R49>). Thus, any additional devices on the Ethernet or CAN-bus must not provide command signals that do not originate from the cRIO-FRC It is our intent to incrementally open access to the full control system technologies in a controlled manner that reduces the risk of “unanticipated surprises” as we gain experience with the system.