user-defined functions in Arduino sketches living with the lab © 2012 David Hall

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example sketch without user-defined functions #include Servo myservo1; Servo myservo2; int whisker1=0; void setup() { pinMode(7,INPUT); myservo1.attach(2); myservo2.attach(3); } void loop() { whisker1=digitalRead(7); if (whisker1==HIGH) { myservo1.writeMicroseconds(1300); myservo2.writeMicroseconds(1700); delay(2000); } else { myservo1.writeMicroseconds(1700); myservo2.writeMicroseconds(1300); } when whisker 1 is pressed, back up for 2 seconds else go forward digital pins 2 and 3 will be used to control the servos take input from the whiskers on pin 7 read the state of the whisker on pin 7 (HIGH = pressed and LOW = not pressed) name your servos run this program – you may need to change whisker and servo pin numbers 3 living with the lab

move “forward” and “backward” commands into functions Make these changes. Note that in this case, it may not make sense to use functions. But, if your have a complex program like you will need for the “navigating the engineering disciplines” challenge, structuring your program in this way could simplify and shorten your sketch. #include Servo myservo1; Servo myservo2; int whisker1=0; void setup() { pinMode(7,INPUT); myservo1.attach(2); myservo2.attach(3); } void loop() { whisker1=digitalRead(7); if (whisker1==HIGH) { myservo1.writeMicroseconds(1300); myservo2.writeMicroseconds(1700); delay(2000); } else { myservo1.writeMicroseconds(1700); myservo2.writeMicroseconds(1300); } SAME UPPER PART OF SKETCH void loop() { whisker1=digitalRead(7); if (whisker1==HIGH) { backward(); delay(2000); } else { forward(); } void backward() { myservo1.writeMicroseconds(1300); myservo2.writeMicroseconds(1700); } void forward() { myservo1.writeMicroseconds(1700); myservo2.writeMicroseconds(1300); } call “backward” function call “forward” function “void” means the function doesn’t return anything when it is completed (no numbers are sent back to the loop) 4 living with the lab

more about functions 5 living with the lab

in-class programming challenge Modify the program shown earlier to allow your robot to roam as follows: robot goes forward by default robot backs up and turns right when left whisker is pressed robot backs up and goes left when right whisker is pressed Please use functions for forward, backward, left and right movements. You may test your robot on the floor to see if it works. 6 living with the lab