1. ROBOTC for VEX On-Site Professional Development

2. Lab Procedures Logging onto computers VEX Robots/chargers Headsets
Log in with: teachers / teachers1
VEX Robots/chargers
Make sure during breaks, lunches and end of day to charge your robot
Headsets
Each workstation has two headsets to allow both partners to watch the videos at the same time
Teacher folders and journals

3. ROBOTC this Week There are several versions of ROBOTC on your desktops
This class we will use ROBOTC 3.0 Beta as much as possible

4. Discussion What is a robot? What can you teach with a robot?
Journaling

5. VEX 0.5 PIC System Overview

6. VEX 0.5 PIC Testbed Features: VEX PIC 2 Motors Servo Motor
Ultrasonic Rangefinder
Potentiometer
Ambient Light Sensor
Line Tracking Sensor
Limit Switch
Bumper Switch
RF Receiver
LED

7. VEX 0.5 PIC Overview
Coordinates the flow of information and power on the robot
All electronic components interface with the microcontroller
8 Motor Ports
16 Analog/Digital Ports for Sensors
Rx1 and Rx2 Ports for Radio Control

8. ROBOTC Overview

9. Background Information
ROBOTC is developed specifically with teachers, classrooms, and competitions in mind
Complete programming solution for the VEX PIC, VEX Cortex, and several other popular robot platforms
Approved for VEX Robotics, BEST, TSA and RoboFest Competitions!
Only programming language for the VEX PIC and VEX Cortex with a real-time debugger
You’ll learn more about this feature later on
Very similar to industry-standard C programming
Students get real-world programming experience
Trainer Notes: The next few slides are meant to highlight features in ROBOTC that will help trainees succeed as they program and answer their own questions.

10. Industry Standard Coding
Students that learn ROBOTC Programming are also learning key components of Industry Standard Programming Languages...

11. Industry Standard IDE
Students programming in the ROBOTC IDE are also learning how to use features in Industry Standard IDE’s...

12. Visual Studio IDE and Code

13. ROBOTC IDE and Code

14. ROBOTC Features

15. Platform Type
Trainer Notes: The next few slides are meant to highlight features in ROBOTC that will help trainees succeed as they program and answer their own questions. When beginning to work with ROBOTC, one of the first things users should check is that their Platform Type matches up with the microcontroller their using. Doing so will enable menu options and ROBOTC commands specifically for that microcontroller.
Allows you to toggle ROBOTC’s programming mode between the VEX PIC and VEX Cortex, will enable features and commands for the system

16. ROBOTC Start Page
Trainer Note: PLTW build of ROBOTC now has a special page dedicated to PLTW schools!
Displays the latest ROBOTC news, version of ROBOTC, and ROBOTC Resources

17. Sample Programs
Trainer Notes: One of the easiest ways to begin programming is to start with existing code, try it out, and then modify it. Mention that all of the ROBOTC sample programs have “comments” that tell how the robot should be configured, and how it will behave when the program runs.
Over 75 Included ROBOTC Sample programs, organized by robot behavior

18. 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 – everything after “//” is ignored by the ROBOTC compiler
/* Multi-line comment*/ - everything between the “/*” and “*/” symbols is ignored by the ROBOTC compiler

19. ROBOTC Help
In-depth explanations about the ROBOTC interface, commands, debugger, etc

20. Function Library Lists the available functions, with a description.
List of available functions will expand or shrink depending on the “Menu Level”

21. Menu Level
Customizes the ROBOTC interface and Function Library based on the user’s experience level

22. Motors and Sensor Setup
One central place to configure and name all of the motors and sensors attached to your Cortex

23. Teaching ROBOTC for IFI VEX Robots

25. Teaching ROBOTC for IFI VEX Robots (TRC4V)
40 tutorial videos
275 pages of printable guides aligned to the videos
50 pages of supplementary “helper guides”
35 programming challenges
Freely available at

26. Student-Paced Instruction
Everyone learns different things at different paces
Everyone MUST move at a different pace
Going too fast results in failure and frustration
Going too slow results in loss of attention (i.e. future failure)
TRC4V can be used as a teaching aid
One instructor can’t teach at 20 different paces simultaneously
One instructor plus 20 computers can

27. System Configuration

28. Downloading Firmware What is Firmware?
Step 1: Download Master Firmware
Step 2: Download ROBOTC Firmware
Step 3: Power-cycle the VEX

29. ROBOTC “Natural Language”

30. ROBOTC Natural Language
Goal is to lower the barrier of entry into syntax-based programming by simplifying the code and using more “natural” command names
Lines of code for common robot behaviors are consolidated into single commands
forward();
lineTrackforTime();
stop();
untilBump();

31. ROBOTC Natural Language
The Natural Language is an additional Platform Type in ROBOTC:

32. ROBOT Motion
Commands that cause the entire robot to perform a behavior

33. Setup
Allows you to specify what type of robot configuration you have from pre-specified models (RECBOT, Swervebot)

34. Movement
Commands that allow you to control individual motors / servos

35. Special
Commands that control the more unique VEX Hardware – LED’s and Flashlights

36. Until
Commands that allow you to create behaviors where the robot acts “until” a certain event
Button Press
Encoder Count Reached

37. Wait
Commands that wait for an elapsed amount of time in seconds or milliseconds

38. Sample Programs

39. Moving Forward and Backward

40. Basic Programming: Motor and Wait Commands

41. VEX Motors
3 Main Types:
Original 3-wire motor
Newer 2-wire motor 269
Newer 2-wire motor 393
All motors are programmed the same way in ROBOTC
Accept values between 127 (full forward) and -127 (full reverse)

42. Motor 2 for 5 Seconds
Displays configuration changes from the Motors and Sensors Setup
Defines the “main task” of the robot
All commands belonging to task main must be in-between these curly braces

43. Motor 2 for 5 Seconds
Turns the port2 rightMotor on at half power forward

44. Motor 2 for 5 Seconds
Causes the robot to wait here in the program for 5.0 seconds

45. Motor 2 for 5 Seconds End Result: rightMotor spins for 5.0 seconds.
Trainer Notes: Draw attention to which lines have semicolons at the end, and which don’t. This will be important when we hit while loops and if statements. In general, single commands or statements get semicolons. Things that change the flow or structure of a program do not get semicolons.
Stops the port2 rightMotor.
End Result: rightMotor spins for 5.0 seconds.

46. Quick ROBOTC Exercise
Create this program yourself and download it to the Robot
Using the Program Debug Window
Trainer Notes: This slide is meant to be a class activity, for trainees to actually get some guided experience with the ROBOTC interface, ROBOTC Commands, Cortex system, ect. The steps should be:
Open ROBOTC
Verify the Platform Type is set to Cortex Natural Language Library
Create the Program
Connect the Cortex to the Computer (via USB or VEXnet)
Turn on the Cortex
Go to Robot > Compile and Download Program
Run the program – Observe the testbed
Turn on leftMotor in the program, after rightMotor and before the wait command (left motor should also be turned off after the wait command).
Compile and Download the Program
Run the Program – observe the testbed
Reverse the motor powers for both motors
Download and run the program – observe the motors spinning in the other direction.

47. Renaming and Reversing
Robot > Motors and Sensors Setup
Optional with Motors (not Sensors)
Giving Motors custom names
Reversing motor polarity
Trainer Notes: Recbot needs to have Port 2 reversed, but Swervebot needs Port 3 reversed. No Reversal needed with Testbed.

48. Naming Rules
The Motors and Sensor Setup window allows you to give your motors and sensors custom names. The names, however:
Should be descriptive of the sensor or motor they refer to (rightMotor, frontBumper, ect.)
Must be all one word made up of letters, numbers, and underscores
Must contain no special characters (&, $, /, ect.)
Cannot already be a ROBOTC reserved word (task, motor, true)

49. Quick ROBOTC Exercise Make Changes to the Program Turn on leftMotor
Download and watch result
Reverse both motors
Trainer Notes: This slide is meant to be a class activity, for trainees to actually get some guided experience with the ROBOTC interface, ROBOTC Commands, Cortex system, ect. The steps should be:
Open ROBOTC
Verify the Platform Type is set to Cortex Natural Language Library
Create the Program
Connect the Cortex to the Computer (via USB or VEXnet)
Turn on the Cortex
Go to Robot > Compile and Download Program
Run the program – Observe the testbed
Turn on leftMotor in the program, after rightMotor and before the wait command (left motor should also be turned off after the wait command).
Compile and Download the Program
Run the Program – observe the testbed
Reverse the motor powers for both motors
Download and run the program – observe the motors spinning in the other direction.

50. Motor Exercises
Turn the rightMotor on forward at full speed for 6 seconds, then stop.
Turn the leftMotor on in reverse at three-fourths speed for 2.5 seconds, then stop.
Turn both motors on at half power for 3 seconds, stop for two seconds, reverse at half power for 3 seconds, then stop.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

52. Servo Motors Very similar in appearance to the normal 3-wire motor
Very different in operation
Rotates between 0 and ~120 degrees
Where the motor is set to a “power value” the servo is set to a “position value”
-127 = 0 degrees, 0 = 60 degrees, 127 = 120 degrees, etc
Servo motors can be programmed exactly the same way as normal motors in ROBOTC, so the programmer must know the hardware and intent
setServo() Natural Language command

53. Servo Exercises
Example: Program the servo to go to position for 2 seconds, position 0 for 2 seconds, and position 127 for 2 seconds.
Individual: Program the servo to go to position for 2 seconds, position -63 for 3 seconds, position 0 for 2 seconds, position 63 for 3 seconds, and position 127 for 2 seconds.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

54. VEX LED Plugged into A/D Port 16 Set as “VEX LED” 1 ON and 0 is OFF
Either ON or OFF
1 ON and 0 is OFF
Red, Green, and Yellow colors available
turnLEDOff(), turnLEDOn NL commands

55. Program Planning
Trainer Notes: The following slides detail program planning. At this point the Program Planning doc can be distributed or referenced during the training. All group exercises should follow the program planning steps to get in the habit of following it.

56. Behavior Based Programming
A behavior is anything your robot does:
turning on a single motor, moving forward, tracking a line, navigating a maze
Three main types of behaviors:
basic behaviors – single commands to the robot (turn on a motor)
simple behaviors – simple task performed by the robot (move forward, track a line)
and complex behaviors – robot performs a complex task (solve the maze)
Complex behaviors can always be broken down into simple behaviors, which are then broken down into basic behaviors
Trainer notes: Supplementary printouts found in the Fundamentals > Introduction to Programming section can be printed and handed outs.

57. The Labyrinth Challenge
Trainer Notes: Introduce the Labyrinth challenge as a possible programming challenge. Additional challenge description / schematic can be found in the VEX Cortex Video Trainer > Movement > Challenge Description Section. This can be printed and handed out, if desired. The Labyrinth was chosen for this example because it allows for a very simple, visual representation of the topics. Things like the PLTW Material Sorter could also be discussed, as that would resonate well with the PLTW network.

58. The Labyrinth Challenge
Trainer notes: this is the path the robot will have to take to complete the labyrinth, broken down from a complex behavior, into simple behaviors

59. Programming Discussion
The Challenge: The Labyrinth
The Solution: ???
The Programmer’s (your) Role
Understanding Program Flow and Behavior Based Programming
Plan out the robot’s path / actions - Pseudocoding
Translate the Pseudocode into real code
The Robot’s role
To carry out your instructions!
The Solution: Programmer and Robot working together, fulfilling their roles
True for all robotic challenges!

60. Pseudocode
Pseudocode is a shorthand notation for programming which uses
informal programming structures (if touch1 is pressed…)
verbal descriptions of code (move forward, stop)
Emphasis is placed on expressing the behavior or outcome of each portion of code rather than on correct syntax (it should be reasonable, though).
Your lines of Pseudocode should also be listed in the same order as they will appear in the ROBOTC Program

61. Pseudocode
Sample Pseudocode:

62. Pseudocode Additional Details:
Pseudocode is used to outline a program before translating it into proper syntax.
Helps in the initial planning of a program, by creating the logical framework and sequence of the code.
An additional benefit is that it can be translated into different programming languages and is therefore somewhat universal.

63. Putting it all Together
Effective Program Planning is essential to writing correct code. Carrying out that plan is equally important!
Once you have your plan, don’t try to implement it all at once!
Systematically add sections of code, testing at every step!

65. ROBOTC Rules/Syntax What does every program have to have?
task main()
Set of "Curly Braces“ {}
In what order does ROBOTC run a program?
Sequentially – Top to Bottom
What is whitespace?
Space in a program to make it easier for a human to read.
Simple Robot Commands (statements) always end with a…?
Semicolon ;

66. ROBOTC Rules/Syntax Paired Punctuation Control Structures Comments
Some functions have "square brackets“ [] , other have "parenthesis“ ()
How do I keep them straight?
Memorization
Functions Library
Control Structures
Just like task main, they have a set of curly braces defining their beginning and end. {}
Example?
Comments
//Necessary Evil
Get into the habit now, or you won't do it ever
Your students learn their habits from you…

67. ROBOTC Rules/Syntax Syntax is the cause of 80% of programming errors…
Most important thing to do when troubleshooting: Check Syntax
Missing Semicolons
Incorrect Braces on Structures
Misspelled words
Improper ‘case’ – motor vs. MoToR
ROBOTC is friendly about most of these errors... but can’t catch everything.

69. Basic Programming: Until Commands
Trainer notes: Hardware available to participants will vary some. In general, the LED is interchangeable with the Flashlight, ec.t

70. The Problem with Wait States
Motor Speed is affected by battery power
If the battery is fully charged, the motors move quickly
If the battery is running low, the motors move slowly
Consequently, the robot will not move consistently as the battery power drains
Anyone experience these effects?
Wouldn’t it be better if we could control how much the robot moves, regardless of how long it took to complete?

71. Sensor Information: Touch Sensors

72. Touch Sensors Touch Sensor Check How they work Two Types Using them
Plugged into A/D 14 & 15
How they work
Digital sensor - Pressed or Released
1 = pressed
0 = released
Two Types
Limit Switches
Bumper Switches
Using them
The SensorValue[] command
untilTouch, untilRelease, untilBump NL commands

73. Touch Sensors Other Properties Limitations
Limit Switch arm can be bent to create a more ideal “hit area”
Both sensors spring back to “open” position
Limitations
Watch out for “bouncing”. As the sensor is pressed or released, it may bounce between 0 and 1 very briefly and quickly.
A very brief wait can be inserted as part of the untilBump() command, or after the untilTouch() and untilRelease() commands to reduce the bouncing effect:

74. Bumper Switch Exercise
Example: Wait for the bumper switch to be “bumped” before the right motor turns on at half power for 5 seconds, then stops.
Individual: Wait for the bumper switch to be “bumped” before both motors turn on at half power, and stay on until the sensor is bumped again. Both motors should then move in reverse at half power for 3.5 seconds.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

76. Sensor Information: Potentiometer

77. Potentiometers Potentiometer Check How they work A/D Port 3
Analog sensor
Measures rotation of a shaft between 0 and ~265 degrees
PIC returns values 0 - ~1023
Cortex returns values 0 - ~4095
Using them
The SensorValue[] command
untilPotentiometerGreaterThan, untilPotentiometerLessThan NL commands

78. Potentiometers Other Properties Limitations
Internal mechanical stops prevent the potentiometer from turning a full revolution.
Limitations
Caution: Excess torque against the internal mechanical stops (can be caused by hand or by a VEX motor) will cause them to wear away. The potentiometer will continue to function, but will have a “dead zone” where the mechanical stops were, where no new values are sent.
Switching the direction the potentiometer is facing will also switch the direction it “counts”. For example: counter-clockwise turns will count 0 to 1023on one side; on the other counter-clockwise turns will count 1023– 0.

79. Potentiometer Exercise
Example: Turn on the LED until the potentiometer value is greater than 512. Then the LED should turn off, and the leftMotor should turn on for 3.5 seconds.
Individual: Turn on the LED until the potentiometer value is greater than 512. Then the LED should turn off, and the leftMotor should turn on until the potentiometer is less than 512.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

80. Sensor Information: Shaft Encoders

81. Quadrature Shaft Encoders
How they work
Digital counting sensor
As the inner shaft spins, the encoder “counts”
Capabilities and Resolution
360 “counts” per revolution of the inner shaft
Counts Up and down
Allows you to control the distance a robot moves, by monitoring how much the wheels spin.
Using them
The SensorValue[] command
untilEncoderCounts, untilRotations, moveStraightforTime, moveStraightforRotations NL commands

82. Shaft Encoders Other Properties
Switching which wire is in the A/D port vs. the INTERRUPT port will reverse the polarity of the encoder (whether it counts up or down for CW turns).
There is an older single-wire version of the encoder, which only counts 90 degrees per revolution of the encoder.
The Natural Language commands automatically clear the encoder for you. Otherwise, clearing the encoders before using them to track rotations is recommended for consistency.

83. Shaft Encoder Exercise
Example: Turn on both motors forward until the encoder has counted 480 degrees.
Individual: Turn on both motors forward until the encoder has counted 480 degrees. Then turn on both motors in reverse until another 3.5 rotations of the encoder have passed.

85. Sensor Information Ultrasonic Rangefinder

86. Ultrasonic Rangefinder
Ultrasonic Rangefinder Check
Output wire plugged into INTERRUPT Port 1 (Input is always first)
Input wire plugged into A/D Port 10
How they work
Similar to how bats and submarines work
Digital sensor – but returns distance values between 0 & 255 inches
(Can also return values of -1 or -2 if used improperly)
Cortex resolution can be in inches, cm, or even mm
Using them
The untilNear and untilFar NL commands

87. Ultrasonic Rangefinder
Other Properties
The Ultrasonic Rangefinder is able to detect objects in a “cone” field of view. As objects get further away, the sensor is able to detect them further away from the center of the sensor.
The sensor bases distance calculations off of sound waves, which means that some objects may not be detectable: soft objects that absorb sound, sharp objects that deflect sound, etc.
Do not use the ultrasonic sensor as the very first command in your code. Until the first sound echo returns to the sensor, it will have a value of -1. A simple delay at the beginning of your program solves this.

88. Ultrasonic Exercise
Example: Turn on both motors until an object is within 10 inches of the sensor, then turn the motors off, and turn the LED on for 6.25 seconds.
Individual: Wait until an object is detected within 15 inches to turn the motors on. Then wait for the object to move more than 20 inches away before turning the motors off.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

90. Sensor Information Line Tracker

91. Line Tracking “Active” Light Sensor Set of 3 Analog Sensors
Sends out a IR beam, and measure how much is reflected back
VEX Cortex returns values between 0 and 4095
VEX PIC returns values between 0 to 1023
Using them
The SensorValue[] command
untilDark, untilLight, lineTrackforDistance, lineTrackforTime NL commands

92. Line Tracking Other Properties
The Line Tracker should be kept between ¼ and 1/8 of an inch of what it’s measuring for the best results.
Constant, consistent lighting is also very important for achieving repeatable robot behavior.
In order to use the Line Tracking sensor(s) you must first calculate a threshold that allows it to distinguish light from dark.

93. Thresholds Overview
A Threshold is a value (usually halfway between) two extremes
Light and dark (Light sensors)
Near and Far (Ultrasonic)
Thresholds allow your robot to make decisions via Boolean Comparisons
Line Following Kits come with 3 sensors
To use all three, you must choose a Threshold that will work with all 3 sensors, or 3 separate Thresholds
The Testbed has only one sensor
You only need to calculate the Threshold for that sensor

94. Threshold Calculation
Calculate an appropriate Threshold with the aid of the Sensor Debug Window
In ROBOTC, create a program that configures your Line Following sensor.
Trainer Notes: The following slides detail the process for determining a threshold.

95. Threshold Calculation
2. Download the Program to the Robot 3. Open the Sensor Debug Window

96. Threshold Calculation
4. Verify that the Program Debug Window’s Refresh Rate does not display “Continuous” and press the Start button. *Press the “Continuous” button if it does.
Trainer Notes: Seeing “Continuous” means that the Sensor debug window will not be seeing continuous updates from the sensors.

97. Threshold Calculation
5. Place a light colored object (or no object) above the line tracking sensor.
6. Record the value for the sensor displayed in the Sensors Debug Window. Only record the value for Analog Port 1 “in1”.
*values displayed will vary from your values

98. Threshold Calculation
7. Place a dark object above the line tracking sensor (or completely block it).
8. Record the value for the sensor displayed in the Sensors Debug Window.
*values displayed will vary from your values

99. Threshold Calculation
9. Add the two values and divide by two. The result is the threshold for that sensor. Light reading + Dark Reading 2
= Threshold
10. Use the threshold(s) in your program

100. Line Tracker Exercise
Example: Move the servo to position 127 until a light object is detected, then have the servo move to position -127.
Individual: Move the servo to position 127 until a dark object is detected, then have the servo move to position -127.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

101. Sensor Information Ambient Light Sensor

102. Ambient Light Sensor “Passive” Light Sensor
Measures the amount of ambient light in its environment
Cortex returns values between 0 and 4095
PIC returns values between 0 and 1023
Range is 0 – 6 feet from the sensor
Using them
The SensorValue[] command
untilDark, untilLight, NL commands

103. Light Sensor Exercise
Example: Program the LED to turn on for 5 seconds when the room lights go out
Individual: Program the LED to turn on when the lights go out, and back off when the lights turn back on.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

104. Decision Making: while loops and Boolean Logic

105. While Loops
A while loop is a structure within ROBOTC which allows a section of code to be repeated as long as a certain condition remains true.
There are three main parts to every while loop.

106. 1. The word “while”
Every while loop begins with the keyword “while”.

107. 2. The Condition
The condition controls how long or how many times a while loop repeats. While the condition is true, the while loop repeats; when the condition is false, the while loop ends and the robot moves on in the program.
The condition is checked every time the loop repeats, before the commands between the curly braces are run.

108. 3. Commands to be Repeated
Commands placed between the curly braces will repeat while the (condition) is true when the program checks at the beginning of each pass through the loop.

109. Boolean Logic
Decisions robots make must always based on questions which have only two possible answers: yes or no, true or false. Statements that can be only true or false are called Boolean statements, and their true-or-false value is called a truth value.

110. Boolean Logic

112. While Loop Exercise 1
Example: Using the Ambient Light Sensor, program the LED to turn on when the lights in the room go out (or the sensor is blocked), and turn back off when the lights are turned back on, forever.
Individual: Expand the previous program to loop only while the limit switch isn’t pressed.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

113. Timers More loop control please? Solution: Timers
Question: Where would the wait statement go if we wanted the loop to repeat for a controlled amount of time?
Answer: Nowhere! We need something else.
Solution: Timers
Can be thought of as internal stopwatches (4 available)
Like encoders, timers should be “cleared” anytime before they are used
Watch where you clear them!

114. Timers
In the program below, timer T1 is used as the condition for the while loop, which will run for 30 seconds:

115. While Loop Exercise 2
Example: Program the greenLED to repeatedly turn on for 2 seconds, then off for 2 seconds, while less than 20 seconds have elapsed.
Individual: Program the servo to go to position 127 for 3 seconds, then position for 3 seconds, while less than 30 seconds have elapsted.
Trainer Notes: Recommend that trainees name their finished programs by the title of the slide, including the number and whether it was a group or individual activity. This will help them refer back to the code later.

116. Decision Making: if, if-else, and Boolean Logic

117. If Statements
When your robot reaches an if Statement in the program, it evaluates the condition contained between the parenthesis.
If the condition is true, any commands between the braces are run.
If the condition is false, those same commands are ignored.
Very similar to how a while loop works, but does not repeat the code!

118. If-else statements
The if-else Statement is an expansion of the basic if Statement.
The “if” section still checks the condition and runs the appropriate commands when it evaluates to true
Using the “else” allows for specific code to be run only when the condition is false.
Either the “if” or the “else” branch is always run; no more, no less.

119. If-else Exercise 1
Example: Program the LED to turn on if the bumperSwitch is pressed, and off if it’s released. Loop Forever.
Individual: Convert the previous program to use an if-else.

120. Multiple If-else Statements
Be careful when using two separate if-else statements, particularly when they are used to control the same mechanism.
One branch of each if-else statement is always run, so you may create a scenario where the two sets of “fight” eachother.

121. Multiple If-else Statements
In this example, if one of the touch sensors is pressed, the rightMotor will be turned on in one if-else statement, and immediately turned off in the other.

122. Multiple If-else Statements
This can be corrected by embedding the second if-else within the else branch of the first, so that it only runs if the first condition is false.

123. If-else Shorthand
An embedded if-else can also be represented as an else if:

124. Closing Thoughts Downloading Firmware ROBOTC Natural Language
Behavior Based Programming
Pseudocode and Program Flow
Basic Motor Commands and Wait States
Until Statements with VEX Sensors
Decision Making

125. Remote Control

126. Remote Control
An out-of-box VEX Microcontroller comes with basic built-in Radio Control functionality
The Radio Control Transmitter can be configured to allow some customization of that built-in functionality
Still very limited customizability and usefulness!
The ROBOTC firmware enables full customization of how the Radio Control Transmitter signals controls the VEX
By default ROBOTC turns off reception from the transmitter to save battery life during autonomous programming
One line of code turns it back on

127. Remote Control
One Transmitter continuously sends out 6 separate values over 6 separate channels
Values range from -127 to 127
Doesn’t something else have values that range from -127 to 127?
The “crystal” number must match on the transmitter and receiver
The crystal is what controls the frequency of the transmission
One transmitter can control multiple robots, so be careful in your classrooms
13 different crystals/frequencies are available

128. Radio Control Reset
Since the Radio Control Transmitter can be configured, there’s the possibility that it’s configured inappropriately for our purposes.
Watch the Radio Control Setup and Values and Axes (Part 1) Videos in TRC4V, found in Radio Control > Control Mapping
Be sure to follow along with the Radio Control Setup Video!

129. Radio Control Signals

130. Remote Control Exercise 1
Example: Implement Basic Remote Control with a while loop.
Individual: Expand the previous program to only run for 30 seconds.

131. Remote Control Direct Value Mapping Program Flow Tracing
Values from the transmitter are directly used to control the motors (1:1 ratio)
Program Flow Tracing
Radio Control with Wait States
Radio Control with a Loop (real-time control)
Indirect Value Mapping
Values from the transmitter are modified before being used to control motors
Can make the robot easier to control
Appropriate in situations that require more “delicate” movements
Notice: the robot reads the right side of the equal sign first

132. Remote Control Exercise 2
Example: Add button control to the basic remote control program so that the servo moves to position 127 when the top Ch5 button is pressed.
Individual: Expand the previous program so that the servo spins to -127 when the bottom button is pressed.