Robot Code Drops Communication or Won't Enable

Symptom: On the field, the robot shows red comms, or it's connected but won't enable, or the drivers' controls do nothing.

Root cause: Communication and enable problems are a chain — laptop -> radio -> roboRIO -> code -> controllers. The Driver Station's status panel mirrors that chain, so debug it top-to-bottom and you'll localize the break fast.

Diagnostic workflow (read the DS indicators in order):

1. Communications red. The roboRIO isn't reachable. At an event, the most common culprits are a Wi-Fi adapter that's still enabled (it fights the field network — disable it), a bad ethernet tether in the pit, or a radio that didn't get configured/powered. Don't use USB RJ-45 extenders; they damage ports and flake out.
2. Communications green, Robot Code red. The roboRIO is up but your program crashed or never started. Open the Console/RioLog and read the stack trace. An uncaught exception in robotInit or a constructor (e.g., a CAN device ID that doesn't exist) takes the whole program down.
3. Code green, Joysticks red/empty. The DS doesn't see your controllers, or they're on the wrong ports. The robot will connect but do nothing. Re-seat USB, and confirm port assignments match your code (new CommandXboxController(0)).
4. Everything green but won't enable. During a match this is the field's job — you're only enabled during AUTO and TELEOP. In the pit, confirm you're not stuck in a disabled mode.

The fix, mapped to the failure:

• Comms: disable Wi-Fi, verify the radio is powered and configured, replace the tether, check the ethernet goes into the correct roboRIO port.
• Code: fix the exception the RioLog names; never deploy code you haven't seen enable on a bench.
• Joysticks: re-seat and re-order USB; lock the port order in the DS USB tab so a re-plug doesn't shuffle them.

Prevent it: Set up the operator laptop per WPILib best practices — high-performance power plan, sleep set to Never, the laptop's firewall configured so it doesn't block DS traffic, updates paused over the event, and the FRC Driver Station kept in focus. Power on and log in before the preceding match ends so you're never scrambling at the field. The fastest comms fix is the one you did in the pit an hour earlier.