FRC Troubleshooting Guide

Symptoms

• Total system failure

Likely cause

Trunk break near start, termination missing, swapped H/L.

Fix

Check connection at Rio/PDH and termination.

Symptoms

• DS connected, but says "No Robot Code"

Likely cause

Code crash, bad deploy, wrong team number/mDNS, or RIO 2.0 bug.

Fix

Check specific "No Code" troubleshooting. If on Rio 2.0, try a reboot (known issue).

Resources

Symptoms

• Everything is acting haunted

Likely cause

Flaky CAN bus affects all devices.

Fix

Check termination (should be 120Ω), wiring integrity, device IDs, and firmware matching.

Resources

Symptoms

• DS is not connected to RoboRIO

Likely cause

Network path failure.

Fix

Follow the USB -> Ethernet -> Radio troubleshooting flow. Verify DS indicators.

Resources

Symptoms

• Robot "dies" under load
• DS shows 12V fault count increasing

Likely cause

Weirdness usually starts with power. Brownouts, battery issues, or loose main leads.

Fix

Check DS logs for brownout markers. Check DS "12V Fault Count". Inspect battery and main breaker connections.

Resources

Symptoms

• Devices vanish
• Red LEDs on components

Likely cause

Loose wiring, missing termination, swapped H/L.

Fix

Verify 120Ω termination at ENDS. Tug-test every junction. Build up bus one device at a time.

Resources

Symptoms

• USB works, Ethernet fails

Likely cause

Network adapter settings or bad cable.

Fix

Validate USB works first. Use RIO webdashboard to verify Ethernet IP. Check adapter settings.

Resources

Symptoms

• CANivore devices missing

Likely cause

Termination config or bus wiring.

Fix

Confirm CANivore termination matches physical wiring (software config).

Resources

Symptoms

• Robot Init... Crash

Likely cause

Exception on enable, Sensor Null/NaN, Thread Starvation.

Fix

Check DS Console/Logs. Guard against nulls. Reduce spam logging.

Symptoms

• Format fail

Likely cause

Firewall, Admin, Safe Mode.

Fix

Boot to Safe Mode and retry as Admin.

Symptoms

• RIO not showing in list

Likely cause

Firewall, AV, or network confusion.

Fix

Run as Admin. Disable Firewall/AV. Ensure only one RIO on network. Try USB.

Resources

Symptoms

• Connection drops when cable moves

Likely cause

Bad RJ45 ends, strained ports, cheap dongles, loose power barrel.

Fix

Swap cables/dongles. Strain-relief EVERYTHING. Zip-tie ethernet at Radio and Rio.

Symptoms

• Spinning in circles

Likely cause

Breaker popped, loose lead, or missing CAN node.

Fix

Check breakers, wiring, and CAN chain for that side.

Symptoms

• Rio CAN ok, Canivore dead

Likely cause

USB issue, Termination, Wrong Bus.

Fix

Check USB, Config, and Bus selection.

Symptoms

• Radio LED status ok, but no ping

Likely cause

Radio config or IP mismatch.

Fix

Re-run radio config utility. Follow model-specific instructions (OM5P vs VH-109).

Resources

Symptoms

• Can ping radio, not rio

Likely cause

Ethernet cable Radio->RIO, or IP mismatch.

Fix

Check cable. key "rio powered but not networking".

Symptoms

• Won't boot normally
• Bricked

Likely cause

Bad image or corruption.

Fix

Boot to Safe Mode (Hold Reset 5s until light stays on). Re-image from Safe Mode.

Resources

Symptoms

• Robot momentarily dies when accelerating
• Weird stuttering

Likely cause

Weak battery, high internal resistance, loose Main Breaker/SB50/Lugs, or mechanical binding.

Fix

Confirm with DS logs (look for brownout markers). Recrimp/replace suspect lugs. Check SB50 tightness/strain relief. Swap battery.

Resources

Symptoms

• Specific LED blink pattern

Likely cause

Misconfigured sensor type or bad cable.

Fix

Reseat/Replace encoder cable. Verify Sensor Type in REV Client.

Symptoms

• Commands sent, nothing happens

Likely cause

Missing 12V (USB only?), Wrong Motor Type (Brushless/Brushed).

Fix

Verify 12V power (not just USB). Check Motor Type config. Read Status LED.

Resources

Symptoms

• DS says "Voltage Brownout"
• RoboRIO power LED turns amber
• Outputs disable

Likely cause

RoboRIO enters brownout protection mode to survive voltage sag.

Fix

Reduce current spikes (ramping, limits). Fix mechanical binding/gearing. Improve wiring (thicker/shorter).

Resources

Symptoms

• Controls feel "floaty"
• Packet loss bars in DS

Likely cause

WiFi interference, wrong band, radio config, laptop power saving, bad ethernet dongle.

Fix

Check DS Log Viewer packet loss. Use wired connection to diagnose. Disable WiFi power saving. Avoid hotspots.

Resources

Symptoms

• Works in Tuner, not in Code

Likely cause

ID mismatch, Wrong Bus (RIO vs CANivore), or Lib version.

Fix

Match ID in code to Tuner. Align library version with firmware.

Symptoms

• Code deploy success, but DS says No Code

Likely cause

Known RoboRIO 2.0 edge case where program doesn't notify DS correctly.

Fix

Reboot the RoboRIO. This is the recommended workaround.

Resources

Symptoms

• Can't find RoboRIO name
• Wrong target IP

Likely cause

Team Number incorrect in DS software.

Fix

Ensure Team Number is set correctly in Driver Station. Use DS to list detected RIOs.

Resources

Symptoms

• Firmware could not be retrieved
• Device blinking red

Likely cause

Wrong ID in code or old firmware.

Fix

Use Phoenix Tuner / REV Hardware Client to verify IDs and update firmware.

Resources

Symptoms

• Fine in air, fails on ground

Likely cause

Real load reveals current draw issues not seen in free-spin.

Fix

Review DS logs after hard driving. Catch failing motors/batteries early.

Resources

Symptoms

• Power LED blinking
• Won't configure

Likely cause

Corrupt/Missing firmware or failure state.

Fix

Reload correct FRC firmware build via config tool.

Resources

Symptoms

• Ethernet perfect, WiFi laggy

Likely cause

RF path issues or interference.

Fix

Verify Band/Channel. Reduce interference (2.4GHz is crowded). Move antenna away from metal.

Symptoms

• Weird channel readings
• Sticky faults on PDH

Likely cause

Mis-seated breakers, latched faults, or firmware quirks.

Fix

Reseat breakers/fuses. Clear sticky faults via REV Hardware Client. Check channel LED status.

Resources

Symptoms

• Robot drives to Narnia

Likely cause

Units, Feedforward, Gyro Sign, Wheel Diameter.

Fix

Check troubleshooting section for tracking. Verify Kinematics/Units.

Resources

Symptoms

• Inverted driving

Likely cause

Motor inversion or Polarity.

Fix

Invert motor direction or swap polarity. Check encoder phase.

Symptoms

• Preventing future failure

Likely cause

N/A

Fix

Review DS logs EVERY MATCH. Look for voltage sag, current spikes, and packet loss.

Resources

Symptoms

• Loose wires

Likely cause

Vibration and fatigue.

Fix

Strain relief battery leads/SB50. Tug-test CAN and power. Label IDs.

Resources

Symptoms

• USB connected, no motor output

Likely cause

Safety feature. USB is config only.

Fix

Must have 12V main power to drive motor.