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Make sure you have the hardware required, your engineering notebook, and VEXcode V5 ready.

Materials Required:
Quantity Materials Needed
1

VEX V5 Classroom Starter Kit (with up-to-date firmware)
1

VEXcode V5 (latest version, Windows, macOS)
1

Engineering Notebook
1

StopOrDrive project from the previous Play page

The brain's screen can have more than one button.

This activity will let you program the robot to drive forward and turn left or right depending on which side of the brain's screen is pressed.

The three additional types of commands that you will need during this activity are the following:

  • drivetrain.turn(RIGHT)
  • number < 50
  • brain.screen.x_position()

You can use the Help information inside of VEXcode V5 to learn about the instructions.

Image showing the workspace in VEXcode V5 with help notes open for set drive velocity commands

Step 1: Let's start by reviewing the StopOrDrive project.

Let's start by reviewing the StopOrDrive project.

The StopOrDrive project had the Clawbot stop if the screen was pressed, or else it had it drive forward.
The entire screen was one big button, but in this next project, we want half the screen to be one button and the other half to be the other.

Image shows the code in VEXcode V5 where the main() function initializes the robot configuration and enters an infinite loop. The loop checks if the Brain's screen is pressed. If it is pressed and the xPosition is less than 240, the robot turns left and waits until the screen is no longer pressed before continuing. If the xPosition is not less than 240, the robot turns right and similarly waits until the screen is no longer pressed. If the screen is not pressed, the robot drives forward.

In order to split the screen into two buttons, we need to understand more about the layout of the screen.

A grid layout with a blue header labeled 'Row-Column' and the numbers 0:11. The grid is composed of 12 rows and 48 columns, with the first row and column labeled as 'Row 1' and 'Column 1,' respectively. The 12th row is labeled 'Row 12,' and the 48th column is labeled 'Column 48.' The grid dimensions are marked as 480 pixels wide and 240 pixels tall.

  • Notice that the columns increase in number from left to right. The number of columns is 48 and the screen is 480 pixels wide.
  • Write down in your engineering notebook that the x-value on the screen is equal to the number of pixels measured from left to right.
  • What is the x-value of the center of the screen? For this activity, you can focus on the x-axis alone because you only need a left and right button.

Step 2: Programming for two buttons.

  • Save StopOrDrive as the LeftOrRight project.

Image showing the project name in VEXcode V5 changed to LeftOrRight

  • Build the project below. It will have the Clawbot turn left or right when the screen is pressed, depending on the side it is pressed on.

Python code using VEXcode V5. The code begins by importing the VEX library, then starts an infinite loop that checks if the robot's screen is pressed. If the screen is pressed, it checks the x-position of the press. If the press is on the left side (x-position less than 240), the robot turns left and waits while the screen remains pressed. If the press is on the right side, the robot turns right and similarly waits while the screen remains pressed. If the screen is not pressed, the robot drives forward. The loop includes a 5-millisecond wait between each iteration

  • Let's review what this project does.

    It keeps checking if the screen is pressed. If the screen isn't pressed it drives forward, but if it is, it checks where the screen is pressed.

    If the press was on the left side (less than 240), it turns left. Otherwise, it turns right. We don't need another condition for when the x-value is greater than 240 because if it isn't less than 240 (turn left), it must be greater (turn right). We only have two buttons to worry about.

    The while and wait Control commands after each turn have the project wait until the screen is no longer being pressed before continuing.

Annotated Python code using VEXcode V5. The code starts with library imports and the main project code. It enters an infinite loop (while True:) that continually checks if the robot's screen is being pressed. If pressed, the code determines whether the press is on the left side (x_position < 240) or the right side. If on the left, the robot turns left and waits until the screen is no longer pressed. If on the right, the robot turns right and similarly waits. If the screen is not pressed, the robot drives forward. Annotations clarify each step in the code

  • Now that the project is done, download and run it to test how it works.Image of the Toolbar in VEXcode V5 with a red box around the download icon
  • Take notes in your engineering notebook about how the buttons control the movements of the Clawbot.

Step 3: Adjust the project for a better User Experience.

When pressing the screen's buttons from behind the Clawbot as it drove forward, you pressed on the right side of the screen to turn left and on the left side of the screen to turn right. That is not a good User Experience. A User Experience is how well a user can interact with a User Interface to control a computer system. There is more information about User Interfaces in the Apply section of this lab.

In this case, we need to improve the User Interface in order to improve the User Experience.

  • Review the LeftOrRight project and revise it so that when the user presses the buttons from behind the Clawbot, the robot turns right when the user presses the left side of the screen. Or else, the Clawbot turns left.

Image of the left or right project in VEXcode V5 Python

  • Plan, test, and iterate on this project and document in your engineering notebook so that the project makes the Clawbot turn toward the side of the screen that the user is pressing from behind the Clawbot.

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