1. ROBOTC for VEX On-Site Professional Development

2. Troubleshooting
Student: My robot won’t stop turning.

3. Troubleshooting
Student: I used the auto straightening code, and it compiles, it isn’t working, it’s just being weird.

4. Troubleshooting
Student: One of my encoders is counting down even though it’s spinning forward.

5. Troubleshooting
Student: My code won’t compile.

6. Radio Control

7. Radio 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

8. Radio 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

9. 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!

10. Radio Control Signals

11. Radio 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

12. Advanced Radio Control
Attach the Arm!
Use the Transmitter buttons to control the arm
The Transmitter buttons send values of -127, 0, or 127
Would direct mapping or indirect mapping be most appropriate for controlling the arm? Why?
More loop control please?
Is remote controlling the robot forever always appropriate?
Question: Where would the wait statement go if we wanted the robot to be remote controlled 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!

13. Advanced Radio Control
Wasting Time?
The time it takes to turn on the VEX and start Radio Control is wasted time.
Could we make the robot wait to start it’s timer until we were ready? Any ideas?
Wait for a Transmitter Button press
The robot won’t start the timer until we say so
The robot also can’t move until we says so
Program Flow Trace
Could this idea also be used to make a “more friendly” start button on a non-radio controlled robot?
Other ideas of how to improve radio control?
Use the buttons to initiate common actions
Turn 90 degrees, move straight forward, ect

14. Advanced Radio Control
Assigning a function to a button press
Auto pickup

15. Radio Control Challenges
TRC4V Videos (recommended)
Watch remaining Control Mapping videos 3-5
Race to the Finish
Remember to Journal
Remember to Pseudocode
Shut off your transmitter when it’s not in use!
Drastically saves the battery life (and your ears)
The transmitter is always transmitting, even if the robot isn’t on

16. Advanced Radio Control Challenges
TRC4V Videos (recommended)
Watch remaining Radio Control Videos (Control Mapping, Timers, Buttons sections)
Minefield Level 1 Challenge
Remember to Pseudocode
Remember to Journal
RoboDunk
First try it
Tele-Operated,
then Autonomously

17. Competition Templates
VEX Competitions have a “Field Management System” in place
Manages when robots are enabled/disabled
Determines whether the robots are in autonomous/tele-operated mode
A Competition Template is available that can be programmed in to work with the Field Management System
Contains autonomous and tele-operated sections
Found in the Sample Programs > Competition folder

18. Troubleshooting
Student: My loop should only be running for 1 minute, but it never stops.

19. Touch Sensors Touch Sensor Check How they work Two Types
Front sensor plugged into A/D 1
Rear Sensor plugged into A/D 4
How they work
Digital sensor - Pressed or Released
Watch out for “bouncing”
Two Types
Limit Switches – on Squarebot 3.0
Bumper Switches
Setting them up
ROBOTC Motors and Sensors Setup window
Using them
The SensorValue[] command

20. Touch Sensors Start Button Fine-tuned arm control
Remember back to how we used the Transmitter button to start the timer portion of the program. How would we implement the same thing with the limit switch?
Fine-tuned arm control
Using the limit switches to tell the robot when it has reached it’s minimum and maximum points

21. Touch Sensor Challenges
Quick-tap Challenge
Incorporating Sensors, Variables, Loops, If Statements, Timers, Boolean Logic, Pseudocoding, and FUN all into one activity
Addition & Subtraction
Everything you just learned, but with another twist

22. The Ultrasonic Rangefinder
Ultrasonic Rangefinder Check
Input wire plugged into A/D Port 5
Output wire plugged into INT Port 1
How they work
Similar to how bats and submarines work
Digital sensor – but returns distance values between 0 & 255
(Can also return values of -1 or -2 if used improperly)
Resolution is in inches (a value of 5 = 5 inches away)
Setting them up
ROBOTC Motors and Sensors Setup window
Using them
Be careful not to use them immediately as your program starts – they take time to initialize and will return negative values
The SensorValue[] command

23. The Ultrasonic Rangefinder
Forward until Near
Move forward until the robot is “near” an object, then stop
Thresholds
Automatic Pick-up
Forward until Near + picking up the mine
Assign to a button

24. Sensor Challenges TRC4V Videos (recommended)
Watch Remaining Sensing Section Videos
Minefield Level 2 Challenge
Remember to Pseudocode
Remember to Journal
The two are not mutually exclusive!
The Speed of Sound
Sonic Scanner Level 2 (Start)

25. Potentiometers Potentiometer Check How they work Setting them up
Sensor plugged into A/D 1
How they work
Analog sensor
Measures rotation of a shaft between 0 and ~265 degrees
Returns values 0 – ~1023
Internal mechanical stop
Setting them up
ROBOTC Motors and Sensors Setup window
Using Analog and Digital Sensors
Using them
The SensorValue[] command

26. Potentiometers Variable Speed Program Arm Control
Use the rotation of the potentiometer to control how fast the robots motors spin
Arm Control
Instead of using the limit switches, use the potentiometer to control how far the arm is allowed to swing up and down

27. Servo Motors Very similar in appearance to the normal 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, ect
Servo motors are programmed exactly the same way as normal motors in ROBOTC, so the programmer must know the hardware and intent

28. Pneumatics

29. Pneumatics Solenoids operate as Digital Outputs
Are plugged into Analog/Digital Ports
Are set to open by setting them to 1
Are set to close by setting them back to 0
Demo in ROBOTC

30. End of Day Challenge Minefield Level 2
Incorporate an autonomous scoring behavior before your tele-operated code begins
One “mine” should always be in the same place, near the goal