VEX and Robot C

1. VEX and Robot C Chris Patterson Frisco ISD CTE Center Presented by

2. The VEX Kit

3. VEX Robotics Platform:Testbed for Learning Programming

4. VEX Motion Subsystem – Motors • 2-wire motor 269 • Two methods to connect to Cortex • Motor ports 1 and 10 • Motor port 2-9 using Motor Controller 29 • 2-wire motor 393

5. VEX Motion Subsystem – Servos • Similar in appearance to the 3-wire motor • Very different in operation • Rotates between 0 and 120 degrees • Motor is set to a “power value” • Servo is set to a “position value” • -127 = 0 degrees, 0 = 60 degrees, 127 = 120 degrees, etc. • Natural Language command • setServo()

6. VEX Sensors Subsystem • Digital Sensors: -Bumper Switch -Limit Switch -Optical Shaft Encoder -Ultrasonic Range Finder • Analog Sensors: -Light Sensor -Potentiometer -Line follower

7. Robot C and Natural Language

8. Step #1

9. Step #2

10. Step #3

11. PLTW Template

12. Natural Language • In short, Natural Language is a form of C based programming that cuts down on coding and makes things a bit simpler. • For Example, • What do you think startMotor(rightMotor, 127); does?

14. Natural Language - Movement

15. Natural Language -Special

16. Natural Language - Until • The program will wait at the “Until” line of code. Once the condition for that sensor is true, the program continues.

17. Natural Language - Until • For example, what might you expect the following to do? untilTouch(bumpSwitch); startMotor(leftMotor, 63);

18. Basic Output Programming

19. Behavior-Based Programming • A behavior is anything your robot does • Turning on a single motoror servo • Three main types of behaviors • Complex behaviors – Robot performs a complex task (automated fan control) • Simple behaviors – Simple task performed by the robot (fan stops when sensor activated) • Basic behaviors – Single commands to the robot (turn on a motor) • Complex behaviors can always be broken down into simple behaviors, which are then broken down into basic behaviors

20. Basic Output Programming EXAMPLE 1 • Let’s turn on the rightMotor for 4 seconds and then off for 4 seconds. Repeat this operation twice.

21. Basic Output Programming – Example 1

22. Basic Output Programming – Example 2 • Turn on a motor and then wait 5 seconds. Set servo to position 127 for 3 seconds and then position 96 for 4 seconds.

23. Basic Output Programming – Example 2

24. Programming with Sensor Feedback

25. Example 3 • A motor turns on once the bump switch is touched and then turns off once the limit switch is touched.

26. EXAMPLE 3

27. EXAMPLE 4 • A motor turns on clockwise at full power when the potentiometer is greater than 3000 and turns counterclockwise at full power when the potentiometer is less than 2000.

28. Example 4

29. Example 5 - What will this program do?

30. While and If-Else Loops

31. While Loops • While loop is a structure within ROBOTC • Allows a section of code to be repeated as long as a certain condition remains true • Three main parts to every while loop • The word “while” • The condition • Commands to be repeated

32. The Condition • Condition controls how long or how many times a while loop repeats • When condition is true, the while loop repeats • When condition is false, the while loop ends and the remainder of the program executes • Condition is checked once every time loop repeats before commands between curly braces are run

33. Revisit Example 1 EXAMPLE 1 • Let’s turn on the rightMotor for 4 seconds and then off for 4 seconds. Repeat this operation twice. • Instead of running it twice, let’s loop it continuously. (running it twice would require a variable, and we aren’t there quite yet)

34. While Loops – Example 1 Revisited

35. While Loops • The while loop has a true condition so it will always run. If the condition is always true, you cannot leave the while loop. • While loops can be based on a sensor condition as well. For example:

36. While Loops – Using a sensor condition

37. While Loops – Using Multiple Conditions

38. While Loop – Timers as Conditions Timer T1 is used as the condition for the while loop, which will run for 30 seconds

39. If Statements • If statement in the program is evaluated by condition contained in parentheses • If condition is true, commands between braces are run • If condition is false, those commands are ignored • Very similar to how a while loop works, but does not repeat the code

40. If-Else Statements • If-else statement is an expansion of if statement • If checks condition and runs appropriate commands when it evaluates to true • Elseallows code to run when condition is false • Either ifor elsebranch is always run once

41. If Statements Example

42. Let’s revisit Example 4 • A motor turns on clockwise at full power when the potentiometer is greater than 3000 and turns counterclockwise at full power when the potentiometer is less than 2000

43. Example 4 – While loop and If-Else Statements

44. This is just the beginning… • You have been given enough tools to go out and EXPLORE on your own time. • Use the lessons in the PLTW curriculums to try out some of the activities and projects.

45. Questions?