VEX2 Sensors Overview

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Main >> CORTEX >> Sensors Overview

For ROBOTC CORTEX Sensor functions, check out the CORTEX Sensor Functions page!

The VEX 2.0 Cortex is equipped with 20 sensor ports. There are 8 Analog Sensor Ports and 12 Digital Sensor Ports. Note that unlike the VEX - PIC microcontroller, all Analog sensors must be in Analog ports, while all Digital sensors must be in Digital ports.

There are a variety of functions and variables used for configuring these ports and accessing their values.

Configuring sensors can be complicated. ROBOTC has a built-in wizard that can be used to configure the VEX 2.0 Cortex sensors. The wizard contains a number of PC windows that allow you to set the following fields for the sensor:

  • The variable name that you want to assign to the sensor. Using a name like “leftBumper” makes for a more readable program than 'dgtl3'!
  • The port that the sensor is connected to.
  • The type of sensor – touch, quadrature encoder, sonar, line follower, etc.

Analog Sensors

There are 5 main types of Analog Sensors for the VEX CORTEX:


The Reflection sensor, also known as the Line Follower, returns values ranging between 0 and 4095. 0 is the lightest reading and 4095 is the darkest.

#pragma config(Sensor, in1,    lineFollower,   sensorLineFollower)
//*!!Code automatically generated by 'ROBOTC' configuration wizard               !!*//
task main
  wait1Msec(2000);                // wait 2 seconds before exectuing following code
  bMotorReflected[port2] = true;  // reflects direction of motor on port 2
  while(true)                     // infinite loop:
    if(SensorValue(lineFollower) < 950) // if the lineFollower sensor reads a value less than 950:
      // turn left:
      motor[port2] = 50;  // motor on port 2 is run at power level 50
      motor[port3] = 0;   // motor on port 3 is stopped at power level 0
    else  // lineFollower sensor reads a value greater than or equal to 950:
      motor[port2] = 0;   // motor on port 2 is stopped at power level 0
      motor[port3] = 50;  // motor on port 3 is run at power level 50

File:Vex reflection.png


Line Follower



#pragma config(Sensor, S1,     touchSensor,         sensorTouch)
//*!!Code automatically generated by 'ROBOTC' configuration wizard               !!*//
task main()
  while(SensorValue(touchSensor) == 0)  // while the Touch Sensor is inactive (hasn't been pressed):
    // DO NOTHING (wait for press)
  while(SensorValue(touchSensor) == 1)  // while the Touch Sensor is active (pressed):
    // DO NOTHING (wait for release)
                                        // otherwise (the touch sensor has been activated [pressed] ):
  motor[motorB] = 75;                   /* run motors B and C forwards */
  motor[motorC] = 75;                   /* with a power level of 75    */
  wait1Msec(1000);                      // wait 1000 milliseconds (1 second) before moving to further code