ROBOTC Software

1. ROBOTC Software Introduction

2. ROBOTC Software • ROBOTC developed specifically for classrooms and competitions • Complete programming solution for VEX Cortex and several other popular robot platforms • Real-time debugger • Similar to industry-standard C programming

3. Industry Standard Coding • ROBOTC programming is a key components of industry standard programming languages

4. Sample Program // sample comments to describe behaviortask main(){startMotor(rightMotor, 63);wait();stopMotor(rightMotor);}

5. Statements and Expressions • Statements are the smallest complete unit of a working program. • Statements primarily consist of expressions, keywords and operators • Expressions may consist of keywords, operators, values, variables, etc. • Example:int length =2*12; // convert feet to inches

6. Comments • Comments are used to make notes in code for the human programmers • Every sample program contains comments pertaining to robot configuration, ROBOTC commands, robot behavior, etc. • // Single line comment – All material after “//” is ignored by the ROBOTC compiler • /* Multi-line comment*/ – All material between the “/*” and “*/” symbols is ignored by the ROBOTC compiler

7. Keywords • Keywords are specific directives that mean something special to the ROBOTC compiler • They are sometimes called reserved words because the compiler “reserves” those words and they can not be used for any other purpose. • Some keywords you will see: #pragma, task,

8. Operators • Similar in behavior to a mathematical function: Examples: 1 + 2 or ADD(1,2) • They commonly take one or more operands and produce a result • Foundational to building expressions and statements

9. Simplified Order of Operations More info: http://en.wikipedia.org/wiki/Order_of_operations *Note: this also depends on pre versus post behavior

10. Variables • A variable is a special form of a label that allows you to reference a value in memory by a name instead of just a location • Variables are “variable” by nature – their contents can usually be changed • Variables can improve the readability and expandability of your programs • To change the value of variable:intdistance = 500; // declare and set

11. Creating a Variable • Declare the variable (stating its type and its name) once at the beginning of task main: • Type of data: • int • float • Name of variable: • Starts with letter • Letters, numbers, and underscores are ok • Not a reserved word

12. Variable Types

13. Assigning a Value to a Variable • The assignment operator is the single equal sign • The right-hand side of the equal sign is evaluated, and then the value is assigned to variable on the left-hand side • This is not the equality from algebra! Declaration Initialization Assignment Assignment

14. Variable Applications • Variables are needed for most programs. Here are some examples: • Example #1: Repeat code 5 times • Example #2: Count user’s button presses • Example #3: Remember if the user EVER pushed a button • Example #4: Remember a maximum value • Example #5: Debug a program by remembering which branch of code has been executed.

15. Global vs. Local Variables • Variables can have either a “global” or a “local” scope. • Global variable • Can be read or changed from any task or function in your code. • Its value can be seen/read globally. • Local variable • Belongs only to the task or function in which it was created • Value can only be read or changed from within that task or function • Value can only be seen/read locally • Generally the type of variable you’ll want to use, local to “main”

16. Functions • Functions • Group together several lines of code • Referenced many times in task main or in other functions • Creating Functions Example: LED on if bumper is pressed, off if released • Function header (name of function) • Function definition (code in the function) • Function call (where function code will run)

17. Function Definition • Function definitions definethe code that belongs to the function

18. Function Call • Function calls • Call and run code from function • Placed in task main or other functions

19. 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

20. 2. The Condition • Condition is an expression that controls 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

21. Boolean Logic • Program decisions are always based on questions • Only two possible answers • yes or no • true or false • Statements that can be only true or false are called Boolean statements • Their true-or-false value is called a truth value.

22. Boolean Logic

23. Writing a condition: Example • While the bump switch is not pressed: • wait until it’s dark, then turn on light; • wait until it’s light, then turn off light

24. Timers • Loop control • Where would the wait statement go if we wanted the loop to repeat for a controlled amount of time? • Nowhere! We need something else. • Solution: Timers • Internal stopwatches (4 available) • Like encoders, timers should be cleared before they are used • Be careful: don’t clear a timer in a timed loop

25. Timers Timer T1 is used as the condition for the while loop, which will run for 30 seconds

26. 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

27. 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

28. Multiple If-Else Statements • Be careful when using two separate if-elsestatements, particularly if both are used to control the same mechanism • One branch of each if-else statement is always run so that you may create a scenario where the two statements ‘fight’ one another

29. 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

30. Program Design • Many basic behaviors generally come together to create a complex behavior. • Troubleshoot basic behaviors as they come together to form a complex behavior.

31. Complex Behaviors • Describe the task or overall goal that your program will accomplish. • A fan will run until someone needs it to stop. A safety device warning light will come on before the fan turns on. Another light will indicate that the fan has stopped. • This may be described as one or more complex behaviors.

32. Simple Behaviors • Break each complex behavior down into simple behaviors. • List the behaviors line by line in the order that each should occur. • Describe actions and what prompts each action to continue.

33. Basic Behaviors • Break each simple behavior down further into basic behaviors. • Think in terms of what each input and output component will be on your device.

34. Program Design • Code and test small behaviors or sets of behaviors individually. • Edit or add comments as you build code.

35. Program Design • Continue programming while testing one behavior at a time. • Temporarily turn sections of code into comments using /* followed by */.