Brain User Interface

Overview#

The VEX Brain is the central computer of your robot. It has a touchscreen display on the front that shows menus, sensor readings, motor status, and program output. Learning to use the Brain screen well will save you a lot of debugging time.

Why does this matter?

The Brain screen is your window into what your robot is actually doing. When something goes wrong, the Brain screen is usually the fastest place to start looking for the cause.

The Home Screen#

When the Brain powers on, it shows the home screen with:

• Battery level — top right corner. Always check this before running. Low battery causes motors to behave inconsistently and sensors to give bad readings.
• Selected program — the name of the last program loaded.
• Smart port indicators — small colored squares showing which ports have connected devices.

A green port indicator means the device is connected and working correctly.
A yellow or red indicator means the device has a problem — check the cable.

The Dashboard#

Press Dashboard on the home screen to see live readings for every connected device. This is the most useful screen for debugging.

What you will see#

• Each motor: current speed (RPM), current draw (Amps), position (degrees), temperature
• Each sensor: current reading in the appropriate unit (mm for distance, degrees for inertial, etc.)
• Battery: exact voltage and charge percentage

Use the dashboard to:

• Verify a sensor is plugged in and giving reasonable values before writing any code
• Check that all motors are connected to the correct ports
• Watch motor current draw during a mechanism test — if current spikes too high, the mechanism is binding

The Devices Screen (Port Configuration)#

Press Devices on the home screen to see all 12 smart ports (V5) or 12 smart ports (IQ).

For each port, you can see:

• What device is connected
• Device firmware version
• Any fault status

Use this screen to:

• Confirm a device is recognized before troubleshooting in code
• Identify a bad cable (port shows “No Device” when you expect a motor)
• Update device firmware

Running Programs#

To run a program on the Brain:

1. From the home screen, select the program name.
2. Press the Play button (triangle).
3. To stop, press the X button or tap the Brain screen.

You can also download and run programs directly from VEXcode — click the Download button to send the program to the Brain, and the Run button to start it immediately.

Using the Brain Screen in Your Programs#

You can print custom text and values to the Brain screen from your code. This is extremely useful for debugging — print sensor values, motor states, and variable values so you can see what is happening in real time.

VEX IQ Python#

# Clear the screen first
brain.screen.clear_screen()

# Print text at the current cursor position
brain.screen.print("Hello World!")

# Move to the next line
brain.screen.next_row()

# Print a variable value
brain.screen.print("Speed: ", left_motor.velocity(PERCENT))

# Move the cursor to a specific row and column
brain.screen.set_cursor(3, 1)
brain.screen.print("Heading: ", inertial.heading())

VEX V5 C++#

// Clear the screen
Brain.Screen.clearScreen();

// Print at current position
Brain.Screen.print("Hello World!");

// Move cursor to row 2, column 1
Brain.Screen.setCursor(2, 1);
Brain.Screen.print("Speed: %d", LeftMotor.velocity(percent));

// Print on row 3
Brain.Screen.setCursor(3, 1);
Brain.Screen.print("Heading: %.1f", InertialSensor.heading());

What to Print During Autonomous#

Print these values to make debugging much faster:

• Current motor encoder positions
• Inertial sensor heading
• Distance sensor reading
• Which step of the autonomous routine is currently running

# VEX IQ Python — useful autonomous debug display
def update_screen():
    brain.screen.clear_screen()
    brain.screen.set_cursor(1, 1)
    brain.screen.print("Step: ", current_step)
    brain.screen.set_cursor(2, 1)
    brain.screen.print("Heading: ", inertial.heading())
    brain.screen.set_cursor(3, 1)
    brain.screen.print("L enc: ", left_motor.position(DEGREES))
    brain.screen.set_cursor(4, 1)
    brain.screen.print("R enc: ", right_motor.position(DEGREES))

Firmware Updates#

VEX releases firmware updates for the Brain, motors, and sensors. Keeping firmware up to date is important — updates fix bugs and sometimes improve performance.

To update firmware:

1. Connect the Brain to your laptop with a USB cable.
2. Open VEXcode.
3. VEXcode will prompt you to update if a new version is available.
4. Follow the on-screen instructions. Do not unplug the cable during an update.

Common Brain Screen Error Messages#

Related Topics#

• Hardware: The Brain
• Hardware: VEX Controller
• Resources: Troubleshooting Guide