Static, disconnects and troubleshooting

"The robot disconnected" is a symptom, not a diagnosis. It can mean the battery came loose, the voltage sagged, static zapped the electronics, the Wi-Fi was swamped, or the code crashed. Teams that fix disconnects quickly are not luckier — they check causes in a fixed order and change one thing at a time.

Static electricity (ESD)

FIRST's guide to managing electrostatic discharge explains how it happens on an FTC field. As wheels — especially wheels that slide across the foam tiles, like mecanum rollers — rub along the floor, charge separates: the robot charges one way and the tiles the other. The voltage can reach tens of kilovolts. When the charged robot touches something, or the charge jumps a gap of more than about 10 mm (3/8"), it discharges in a sudden spike of current.

That spike can:

• reset or disrupt the control system,
• cause Wi-Fi disconnects,
• reset the IMU, so heading suddenly jumps, and
• damage electronics.

How to protect your robot

These are the mitigations from FIRST's ESD guide and REV's troubleshooting pages:

The resistive grounding strap

Normally the robot's frame must be electrically isolated from all wiring — the frame may never carry current (rule R605 in 2026–27). The one exception is an approved resistive grounding strap, which connects the electronics' ground to the frame through a resistor. REV describes its strap's 470Ω resistor as minimising high-energy discharges between the electronics and the frame: charge bleeds off gradually instead of arcing.

The 2026–27 manual lists the AndyMark (am-4648a), REV (REV-31-1269) and Swyft (SR-Ground-01) straps as approved. The strap must plug into a spare XT30 port on a fully off-the-shelf device (for example a hub's spare XT30), and its other end must bolt directly to the frame. Nothing on the robot may be designed to ground the frame to the field.

FIRST also gives a test to confirm the frame is isolated: with the battery unplugged, use a multimeter to check for more than 120Ω between the main switch's input terminals (red with the switch on, and black) and any metal point on the robot. Some cameras, LEDs and sensors have metal or conductive cases — those must be isolated from the frame too.

When the IMU resets

REV and FIRST received reports of Control Hub IMUs resetting after static discharges during the 2023–24 season. REV's advice: keep the Control Hub operating system up to date (OS 1.1.4 added a fix that reduces these resets), use the ESD steps above, make sure the battery connection is secure and the battery charged, and give drivers a button that re-initialises the IMU — ideally with the robot squared up to the tile seams.

What actually causes disconnects

Sort the cause into one of four buckets:

Bucket	Typical signs	First checks
Power	Happens when mechanisms run or the robot is hit; voltage dips on the Driver Station	Battery charge, XT30 connections, switch, brownout symptoms
Static	Happens on the competition field more than at home; after contact with the field or another robot	ESD mitigations, grounding strap, USB 3.0 port
Wi-Fi	Ping is high or erratic; happens at school or crowded venues; no voltage change	Channel and band, Control Hub placement, other devices on the network
Software	The OpMode stops with an error message; the robot stays connected but does nothing	The error text, the Robot Controller log

Wi-Fi checklist

• Use 5 GHz if your Driver Station supports it. REV recommends the 5 GHz band for dual-band Driver Stations.
• Pick a quieter channel. REV suggests using a Wi-Fi analyser to find a channel with less overlap. At events, staff may assign you a band or channel, and you must use it.
• Place the Control Hub well. FIRST's wiring guide says to mount it where large metal parts, the battery and motors do not block or interfere with the radio, and where other robots cannot hit it.
• Keep everything else off the robot's network. During matches, only the Driver Station may be connected — disconnect programming laptops.
• Keep software matching and current. FIRST recommends that the Robot Controller and Driver Station app versions match.

Read the Control Hub's status LED

The RGB LED near the RS485 ports is REV's "check engine light". With current software:

LED	Meaning
Solid green	Powered and communicating normally
Solid blue	Powered, battery above 7V, waiting for communication
Blinking blue	Keep-alive timed out — communication was lost; clears when it resumes
Blinking orange	Battery below 7V — charge the battery

The troubleshooting order

REV's general advice is to isolate the issue: many faults produce the same symptom, so eliminate possible causes one at a time. Use this order, cheapest and most likely first:

Pull the logs

The Robot Controller log records what the robot was doing, with timestamps, including errors and disconnects. REV lists several ways to get it:

• Robot Controller Console: connect to the Control Hub's Wi-Fi, open the console in a browser, go to the Manage page, and press Download Logs.
• REV Hardware Client (Windows): its Log Viewer filters and searches log files, and it can send diagnostics to REV support.
• USB file browsing: plug the Control Hub into a computer by USB-C and open its internal storage; the logs are text files at the top level. On a Mac you need the Android File Transfer app.

Note the match time when something goes wrong, then look at the log around that timestamp.

Check yourself

A teammate wants to reduce static by bolting a plain wire from the battery's negative lead to the robot frame. Is that OK?

• AYes — grounding is grounding
• BNo — only an approved resistive grounding strap, plugged into a spare XT30 port on an off-the-shelf device, is allowed
• CYes, as long as the wire is 18 AWG
• DOnly if the frame is painted

Check yourself

Your lift motor stopped responding before a match. Which check should come first?

• ARewrite the lift code
• BChange the Wi-Fi channel
• CCheck the battery and the lift motor's power cable and port
• DReplace the Control Hub

Check yourself

Mid-practice the robot stops, and the Control Hub's LED is blinking orange. What does it mean?

• AThe battery voltage is below 7V
• BThe Wi-Fi channel is congested
• CA firmware update is running
• DEverything is fine

Next

A robot that stays connected still has to be allowed on the field. The last lesson walks through electrical inspection.

Sources and further reading

• FTC Docs: Managing ESD — how robots charge, symptoms and mitigations
• FIRST Robot Best Practices — frame isolation test, software versions
• FIRST Robot Wiring Guide — ESD wiring tips, Control Hub placement
• REV: General Troubleshooting — ESD mitigation, grounding strap, isolating the issue
• REV: Control Hub Troubleshooting — Wi-Fi, brownouts, XT30 pins
• REV: Status LED blink codes
• REV: IMU — protecting the IMU from ESD
• REV: Accessing log files
• REV Resistive Grounding Strap (REV-31-1269)
• FTC Competition Manual — rules R605 and R704