Ultrasonic Rangefinder Forward till Near - ROBOTC.net

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Sensing Ultrasonic Rangefinder Forward till Near (cont.) Checkpoint © Carnegie Mellon Robotics Academy / For use with VEX ® Robotics Systems 4b. Select A/D Sensors 1-8 ROBOTC 4c. Set the sensor Name to “sonarSensor” The Ultrasonic Rangefinder is indexed by the number of the Analog/Digital Port it is plugged into, so enter a name for the sensor under Analog/Digital Port in5. 4d. Set the sensor Type to “SONAR” Set the type of the sensor to “SONAR”, another name for the Ultrasonic Rangefinder (because it uses sonar sound waves to measure distance). 4e. Configure the Second Port to “int1” When you select “SONAR” as the sensor Type, a column for the “second port” appears for this sensor. The second port is the other port that the sensor is plugged into, Interrupt 1 (int1). 4f. Click OK Click OK to finish configuring the Ultrasonic Rangefinder. The Ultrasonic Rangefinder is now set up and recognized by the program. It will now provide sensor readings as values through SensorValue[sonarSensor]. The values represent distances to the nearest detectable object (the first echo that the sensor hears), in inches. If an object is 6 inches away, in front of the sensor, SensorValue[sonarSensor] will be 6. Ultrasonic Rangefinder • 4
Sensing Ultrasonic Rangefinder Forward till Near (cont.) Let us first begin by reviewing the way a forward-for-distance Encoder behavior works, and then adapt it to use the Ultrasonic Rangefinder instead. The forward-for-distance command below was taken from the early parts of the Encoder lesson, and moves the robot forward until the Encoder accumulates more than 5000 counts of rotation. It does so by using a while loop to repeat basic movement commands as long as the current count is still below the desired target. while(SensorValue[leftEncoder] < 5000) { motor[port3] = 63; motor[port2] = 63; } In the case of the Ultrasonic Rangefinder moving until the robot is close to an object (such as the “stem” of a mine), we want the robot to move until the detected distance is below the target distance. Rephrased, the robot should keep running as long as the distance to the object is still greater than the desired distance. 5. Add task main and base code. Auto Auto 1 2 3 4 5 const tSensors sonarSensor = (tSensors) in5; task main() { wait1Msec(2000); bMotorReflected[port2] = 1; } 6. Add the basic structure of a move-until behavior. Auto Auto 1 2 3 4 5 6 7 8 9 10 11 const tSensors sonarSensor = (tSensors) in5; task main() { wait1Msec(2000); bMotorReflected[port2] = 1; while() { motor[port3] = 63; motor[port2] = 63; } } © Carnegie Mellon Robotics Academy / For use with VEX ® Robotics Systems 5. Add this code Add task main, an initial delay, and the motor reflection command before proceeding with the rest of the program. 6. Add this code The basic structure of the behavior is a while loop containing movingforward commands. The (condition) will determine how long this loop lasts, and is left blank for now. ROBOTC Ultrasonic Rangefinder • 5
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Ultrasonic Rangefinder Forward till Near - ROBOTC.net

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