2 Be Mindful / Not Random! (be a thinker not a tinker) There are a lot of variables when it comes to programming [ variables hinder troubleshooting ]If you are not mindful of what you do or don’t do, I cannot systematically help you eliminate variables. [ IDK, I think so = frustration for you ]If we can not limit the variables, I cannot help you solve your problem in a timely mannerIf I cannot solve your problem in a timely manner, I will need to move on to the next group
3 Safety Keep long hair clear of your testbed, especially your gears! No plugging or unplugging of anything with the power on! – Turn-off the Cortex 1st!!You could get shocked andhave to pay for anything youdamage (intentional or not)
4 Check your Cortex - Properly inserted plugs? Parallel to top and bottom edgesWhite wire towards the middle
5 Are you ready to program your testbed? If you followed your packet, your software should be set-up, now check your hardware:Hardware Checklist:properly inserted plugs into the cortex (white wire to the middle as shown on the last slide)two motors with motor controllers plugged into motor ports 2 & 3 (red to red & black to black as shown on the next slide)limit switch & bump switch in digital ports 1 & 2
6 Connecting the MotorsTwo-wire motors can be plugged directly into MOTOR ports 1 & 10 on the Cortex, and 2-9 using the Motor Controller 29 – red to red, black to black
7 FYI - VEX Motors 2 Types (labeled on motor): 2-wire motor 269Newer 2-wire motor 393ReviewAll motors have the same values between127 (full forward) and -127 (full reverse)
8 Practice ExerciseCopy the code on the next slide into your RobotC fileTrainer 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 ROBOTCVerify the Platform Type is set to Cortex Natural Language LilbaryCreate the ProgramConnect the Cortex to the Computer (via USB or VEXnet)Turn on the CortexGo to Robot > Compile and Download ProgramRun the program – Observe the testbedTurn on Motor Port 3 in the program, after Motor Port 2 and before the wait commandCompile and Download the ProgramRun the Program – observe the testbedTalk about the testbed design, how the motors are mirrored images of one another – even though you gave them the same motor power, they turn in opposite direction. This is something common on actual robots, where they mirror one another.In ROBOTC, us the Motors and Sensors Setup to reverse the appropriateOptional – rename the motors in the Motors and Sensors SetupDownload and run the program – observe the motors spinning in the same direction.
10 Running a ProgramChoose Robot, compile and download, and start
11 How it worksThe next series of slides explain what is happening
12 Motor for 5 Seconds PRAGMA – generates from motors & sensors setup Displays configuration changes from the Motors and Sensors SetupDefines the “main task” of the robotAll commands belonging to task main must be in-between these curly braces
13 Motor for 5 SecondsTurns the port2 rightMotor on at half power forward
14 Motor for 5 SecondsCauses the robot to wait here in the program for 5.0 seconds
15 Motor for 5 Seconds End Result: rightMotor spins for 5.0 seconds. Stops the port2 rightMotor.End Result: rightMotor spins for 5.0 seconds.
16 Modify the code from the practice activity so it works for the 1st programing exercise on the next slide.
17 Motor Exercises [1 of 6]Turn the rightMotor on forward at half speed for 5 seconds, then stop.Turn the leftMotor on in reverse at three-fourths speed for 2.5 seconds, then stop.Turn both motors on at full power, and spinning in the same direction, for 7.25 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.Teacher initial ____________
19 Touch Sensors Touch Sensor Check How they work Two Types Plugged into Digital 1 & 2How they workDigital sensor - Pressed or Released1 = pressed0 = releasedTwo TypesLimit SwitchesBumper SwitchesA very brief wait can be inserted after touch sensor related commands to reduce the bouncing effect:( bumpSwitch ) ;
20 Use a combination of the practice code from earlier and the bumpswitch code on the last slide to complete the programing exercise on the next slide
21 Bump Switch Exercise [2 of 6] Exercise: Program the rightMotor to turn on at half power, until the bump switch is pressed. The motor should then stop.
22 Use your limit switch to complete the exercise on the next slide Instead of bumping the bumpSwitch, your are bumping the limitSwitch
23 Limit Switch Exercise [3 of 6] Wait for the limit switch to be touched before the right motor turns on at half power for 5 seconds, then stops.Wait for the limit switch to be touched before both motors turn on at half power, until the sensor is bumped again. Both motors should then move in reverse at half power for 3.5 seconds.Discuss how the limit and bump switch would be used for Grandmas Chair, Toll booth, Sign, Tekrocks Bridge
24 VEX LEDPlugged into DIGITAL Port 12 (with an extension see next slide)Set as “VEX LED”Red, Green, and Yellow colors available
25 VEX LED Connect the LED to the PWM Extension wire. Turn-off the cortex! – no plugging orunplugging of anything with the power on!The outer terminal on the LED should be plugged in on the white wire.The center terminal on the LED shouldbe plugged in on the red wire.The black wire should have nothingconnected.
27 While LoopsA 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.
28 1. The word “while”Every while loop begins with the keyword “while”.
29 2. The ConditionThe 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.
30 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.
32 1. while() Loops do NOT Constantly Check their Conditions while() loops check their conditions before running the body of codeAfter the body of code is run, the while() loop checks the condition againThe condition is NOT checked while the body of code is being run
33 2. while() Loops do NOT Keep Programs Running Forever Exception: Infinite while() loopsexample “while (1 == 1)” or “while (true)”Once the while() loop’s condition is met/false, the robot moves past the while loop in the program and does not revisit itStudents often assume that because there is a while() loop in the code, the program keeps on running
34 3. while() Loops are a Programming Structure, not a Command They do not get a semicolon (;) after the conditionAdding a semicolon will cause the while() loop to constantly check the condition, without running the body of code
35 4. All “until” commands in the NL are actually while() loops All “until” commands are just a while() loop with a wait command, to hold the “Program Flow” at that spot in the code
36 Modify the code on the previous slides to complete the exercise on the next slide
37 While Loop Exercise 1 [4 of 6] Example: Program the greenLED to repeatedly turn on for 2 seconds, then off for 2 seconds, while the limit switch isn’t pressed.So pressing the limit switch will stop the led from flashingTrainer 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.
38 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: TimersCan be thought of as internal stopwatches (4 available)Timers should be “cleared” anytime before they are usedWatch where you clear them!
39 TimersIn the program below, timer T1 is used as the condition for the while loop, which will run for 30 seconds:[bumpSwitch] == 1)
40 While Loop Exercise 2 [5 of 6] Program the greenLED to repeatedly turn on for 0.5 seconds, then off for 0.5 seconds, while less than 5 seconds have elapsed.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.
41 If StatementsWhen 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!
42 If-else statementsThe 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 trueUsing 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.
43 If-else if Exercise 1 [6 of 6] Program the greenLED to turn on if the bumpswitch is pressed, and off if it’s released. Loop Forever..