VEX Field Control User Manual


The V5 Competition Field Controller is a standard V5 brain running a modified version of VEXOS that limits its capability to running special programs created by VEX. Some features such as the built in driver control and user program download have been disabled.

The four robots involved in a VRC match are connected to the field control system using smart cables plugged into one of the smart ports on the primary controller. The second available controller smart port is still able to be connected to a partner controller. The autonomous and driver control phases of a match can be directly controlled using the touch screen of the field controller, alternatively the system can be under host control using serial communication through the USB port of the brain.

The V5 field controller is intended to be a replacement for the legacy VEXnet Field Controller, it uses a similar USB connection to either the Tournament Manager PC or Raspberry Pi, but the RJ45 cables have been replaced by VEX smart cables connected to the controller smart port rather than the legacy competition port. It’s recommended that the competition port be disabled by using an RJ45 plug so a smart cable is not accidentally plugged in, potentially causing damage.

System Overview


The field control V5 brain (FC brain) is connected to alliance controllers using smart cables. Blue alliance controllers are connected to any one of the smart ports in the blue labeled groups, that is, one controller connected to a port in the group 6-10 and the other to a port in the group 11-15.


Red alliance teams are connected in a similar way to the two red groups.

The FC brain, although able to be used stand alone in a similar way to a competition switch, will usually be connected to the Tournament Manager match control system (TM). The FC brain is connected to TM using a USB cable to either a Raspberry Pi or to the host PC running the TM server. Connection to a Raspberry Pi is the preferred way of operating the system as the Pi can then be used to drive a display at the field with team and match status.


When the field control program is first executed on the FC brain it will show a splash screen similar to this.


The program has a few user configurable settings, they can only be accessed while the splash screen is being displayed, touch the “settings” on screen button to switch to the settings screen.


1. Radio channel controlled by field activation.

Value Description

The FC brain will handle competition channel selection in the same way as the legacy VEXnet field control system, that is, as soon as a student controller is plugged into the FC brain it will jump to a competition channel that it will automatically select.


The student’s robot will initially stay on a pit radio channel, when TM activates the field, the student robot will jump to a competition channel. This mode minimizes the number of robots actively using competition channels which is important at large events with many fields, however, students may not understand why they briefly lose connection when the field is activated before a match.

2. Radio mode used for skills app.

Value Description

The student’s robot must be set to use the VEXnet radio mode.


The student’s robot must be set to use Bluetooth radio mode

NOTE: This setting only applies to the Robot Skills app. The VRC match app will only require VEXnet.

3. Smartport power.

Value Description

The field control brain will provide power to the student’s controller via the smart port. WARNING: This can cause the field controller brain’s power adapter to overload and power down. It is recommended to use a V5 battery that is connected to a charger when this setting is enabled.


The field control brain will NOT provide power to the student’s controller via the smart port.

To exit the settings screen, press the “done” button. Settings are saved inside the FC brain and will not be lost if the FC program is updated or loaded into a different program slot.

Home screen:


The home screen is shown after the splash screen or settings screen exits. This would be the screen generally displayed during a competition; it shows an overview of team status and also the current match timer when a match is being run. Any errors or warnings shown on this screen are also reported to TM. The TM field queue display is the preferred way to check team status, however, this screen can be used to help diagnose team problems.

Team status is shown in the rectangle next to their connected port, the physical smart port used is shown by the small green rectangle. The outline will be green when a connected team has met all requirements for starting the match.


  1. Robot is connected via radio link to controller.
  2. Robot has met the required firmware version.
  3. A user program is running.

If there is an error, perhaps the team forgot to start their program or their battery is very low, the outline will be shown in orange. TM will show a descriptive error on the field queue display, but the FC brain can also be used to see more detailed information if needed. To see detailed information touch the rectangle with team status and the display will switch to this screen.

Team status is good


Team has an error


Errors are shown in orange, in this case, the team is running old firmware (VEXOS) in their V5 Robot Brain and has also not started their user program. To dismiss the team details touch anywhere on the screen.

Team status:


Status Shows Good
Team number : 8888Z
Robot Battery : 99%
User program : 3 (Slot 3 is running; 0 would be no program running)
Radio channel : 81/5 this is for use by VEX engineering at the VEX World Championship.

See Appendix A for more explanation of the detailed team status page.

Use with Tournament Manager.

When TM is not connected the home screen will have the “auton” and “driver” buttons enabled and the clock display in the upper left corner will generally be gray indicating it has not been set. Using the “Auton” or “Driver” on screen buttons allows the standard 0:15 and 1:45 duration match phases to be manually run (VexU times not supported as yet).

When TM is connected, indication will be shown on the home screen and the buttons will be disabled.


The clock is now shown in green indicating that it has been set. TM connected is shown.

The match number may be set but if the field is inactive it will be in gray, once the field becomes active it will be shown in green.


When robots are disabled the background of the home screen will be black, during the autonomous period when robots are enabled it will be blue and display remaining time.


During the driver control period the background will be green and show remaining time.


The remaining time and robot enable/disable signals are sent from TM to the FC brain. This allows accurate synchronization and duration of autonomous and driver control periods to be under TM control and not determined locally by the FC brain.

Tournament Manager Displays

Tournament Manager will show team status on both the Match control display and also on the field queue display for each configured field. Team status is shown in several colors; before starting a match look for all teams showing “Ready” in green with the field active also in green. Warnings will be shown in yellow; a match can be started when warnings are present but teams should be reminded that robot operation may be impaired depending on what the warning is, for example.


Here one team has forgotten to, or chosen not to run a user program on the robot; all other teams are ready. Team 1234A should be alerted to that fact and if they have chosen to do this the match can start.

This screen shows some of the possible errors that may be displayed.


  • Team 8888Z is ready.
  • Team 1234A has incorrect firmware running on the V5 brain, match control requires VEXOS 1.1.1 or later.
  • Team 99999V has not connected the controller to the FC brain.
  • Team 44 has a fault on the legacy completion port or perhaps a competition switch still connected.

Neither team 99999V or team 44 will be enabled when the match starts.

If TM has become disconnected from an FC brain, the following error screen is displayed.


If the setting on the FC brain, “Radio channel controlled by field enable” is enabled, the following screen will be displayed before a match is set to be “on field”


Teams are shown as “waiting for field activation” if status is good but they have not been switched to the competition radio channel, warnings and errors will still be displayed. If “Radio controlled by field activation” is disabled, a similar screen would show except that teams would be displayed as “Ready” even though the field was in “field standby” mode. As soon as that match was set “on field” then field standby would change to become green and display field active. The active field is the one that will be started when the operator selects “Start Match”.

As soon as a match is started, the field queue display will switch and show remaining match time.

Error Logging

The FC system will log certain data in both the FC brain and the student robot log.

For the student robot, the V5 brain internal timer is updated to match the realtime clock supplied by Tournament Manager. This allows existing log entries; for example, match start, stop and radio connection events to have time of day time stamps. TM also sends event and match information that is recorded into the log. Field control event entries are shown in yellow.


“--> 17:38:53” = This log is showing that the clock time is being set.
“VRC-21-1234” = This log is showing ?????
“Q-0001” = This log is showing that qualification match 1 has been activated.

The FC brain will also log entries using the TM supplied clock. In addition to the above it will also record certain errors that may have occurred during a match; these currently include cable disconnect and radio disconnect errors. When a match ends, if the field is still active, the FC brain may show a warning in this way.


This indicates that either cable or radio disconnect errors occurred while the robots were enabled during the match. If you look at the detailed team status, it will show more information. This example shows the red alliance team #2 had a cable disconnect error, indicated by the red port indicator. Opening the detailed team status would show the number of total errors.


This information is recorded in the FC brain log in this way (VEXOS 1.1.2b3 or later required)


FC log entries are shown in yellow. In this example, red alliance team #2 (R2) had two cable errors, blue alliance team #1 (B1) had two radio disconnect errors.

We realize that it’s not practical to monitor the FC brain for these errors at most competitions unless dedicated field tech staff are available. The primary use of logging is to allow post analysis if there are any unusual situations; for example, perhaps all four robots failed to move during a period of the match. If the log shows all four had radio disconnect errors then that can be factored in when considering possible match replays. Conversely, if a student robot does not move during a match but neither FC or student brain show any log errors and that match phases were correctly started, then the problem is most likely not the fault of the field control system and the students’ robot/code may need to be investigated for possible issues.

Skills App

A variation of the FC program can be used when running skills matches. This version focuses on checking and displaying status for a single (or two for VexU) robot and allows the one minute skills run to be started from the FC brain screen as an alternative to using TM.


The splash screen will show the current radio mode, BLE or VEXnet, that was selected on the settings screen.

When no team controller is connected, a large exclamation mark is shown,


When a team is connected and there is an error or warning, a description is shown. In this example, the robot radio connection has not been established.


When the status is good, a green circle with a check mark is shown.


The skills run can now be started from either the FC brain screen, the TM match control windows or a TM connected tablet. When started from the FC brain screen, a message is sent to TM requesting that the skills run be started, this allows all normal match time displays to run correctly.

The FC screen will show remaining time for the skills run when the robot is enabled.


Appendix A

Description of fields for the detailed team status screen.

This is subject to change. The screen shown is the screen used during the VEX 2022 World Championships but may be simplified for final release of the FC application late summer 2022.


Team 1234A The team number that is reported by the robot
Vexos 1.1.1 The current version of VEXOS installed in the team robot brain
Radio Version 1.0.0b49 The robot radio version (this is currently disabled and will not change)
Radio 81/6 Comp The current radio channel, time slot and mode (Pit or Competition)
Radio Status 003D For use by VEX engineering at this time
System Status 1090 For use by VEX engineering at this time
Program Drive Current user program, 0 not running, slot_1 etc. or Drive
Brain Status 21 For use by VEX engineering at this time, match control mode in brain
Field Status C9 For use by VEX engineering at this time, match control mode in controller
Battery 100% The robot battery capacity
Connection Good Status of radio connection between controller and robot
Ctrl version 1.0.0b75 The version of firmware in the team controller
Ctrl radio 1.0.0b48 The version of firmware in the team controller radio
Ctrl Battery 100% The controller battery level percentage
Signal 95 The radio signal quality percentage
RSSI -54 The radio signal strength in dBm
Radio drops 0 The number of times that radio connection was lost during match play
Match timer 102499 Internal match timer in ms, may be removed, development use
Display 103 Internal match timer that would be displayed on home screen
Cable errors 0 Cable errors 0 The number of times that controller connection was lost during match play; this indicates how many times the smart cable was disconnected from FC

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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