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Coding Fundamentals
Lab 4 - Robot Help

Teacher Portal

Launch the Engage Section

ACTS is what the teacher will do and ASKS is how the teacher will facilitate.

  1. As students give answers based on previous Labs, write them on the board. For those who are struggling with answers or were absent for the other Coding Fundamentals Labs, provide some answers like knowing the intended 123 Robot behaviors and planning a project.
  2. Ensure students understand that these bugs are not like insects or something alive. These are mistakes just like they make mistakes each day.
  3. Clear the board from the above answers and write "How to Debug" to help prepare students for the rest of the Engage section.
  1. What steps should we take to create a project with the Coder and 123 Robot?
  2. Even with all of these steps to plan and make a project, sometime things go wrong and errors happen. These are called bugs! Bugs in projects are just like another mistake.
  3. Mistakes are always okay! You can "debug" and fix a project once you find where that bug is. How can we find the bugs in our projects and fix them, so the 123 Robot does what we want it to?


  1. InstructInstruct students that they are going learn how to debug their projects. They will build a project, start the project and observe the behaviors of the 123 Robot, then step through the project to find the bug.
    • Have all students gather around a demonstration area that includes a Coder, a 123 Robot, access to a 123 Field, and a set of Coder cards.
    • Tell students that you want your 123 Robot to drive from the bottom left square on the 123 Field to the middle of square, as shown here.

    123 Robot in Bottom left corner of tile
    Goal of the Project

    • Create this project in your Coder using the matching Coder cards and show students the project in the Coder.

    Coder Robot

    Coder card Project
    • Wake and connect the 123 Robot. Have students describe the steps to for waking and connecting, as students have practiced in previous labs. To wake the 123 Robot, push the wheels along a surface until you hear the startup sound, as shown in the animation below. Turn on sound for this animation. For more information about the 123 Robot, see the Using the VEX 123 Robot VEX Library article.
    Video file
    • Then connect the 123 Robot to the Coder. Have students describe the steps that they have learned to connect the robot in previous labs: press and hold the Start and Stop buttons on the Coder, and the Left and Right buttons on the 123 Robot for at least 5 seconds, until you hear the connected sound, and the indicator lights flash in time, as shown in the animation below. Turn on sound for this animation. For more information about the Coder, see the Using the VEX 123 Coder VEX Library article.
    Video file
    • Have students observe the movement of the 123 Robot. The 123 Robot will drive past the center square.
    • Tell students that they can use the "Step" button on the Coder to move one card at a time through the project. Show students how to select the Step button to use the Step feature on the Coder to execute one card at a time to identify where the bug is in the project. Students should identify that the last Coder card makes the 123 Robot drive too far forward.

    Step button
    Step Feature on the Coder

    • Once you have found the bug, show students how to switch the last Coder card to a "Drive 1" and test the project. The 123 Robot should drive from the bottom right corner of the Field to the center square.
  2. DistributeDistribute distribute a 123 Robot, Coder, 123 Field, and a set of Coder cards for demonstration purposes. Also set out the following Coder cards:
    • One "When start 123"
    • Two "Drive 1"
    • One "Drive 4"
    • One "Turn left"
    • One "Turn right"
  3. FacilitateFacilitate a discussion with students as they observe the movement of the 123 Robot.
    • What Coder card needs to be fixed so the 123 Robot drives to the center square?
    • How does the step feature help us find the mistakes or "bugs" in a project?
  4. OfferOffer students additional practice decoding a project if they are struggling with how to find and fix a bug in a project.
A VEX 123 character

Teacher Troubleshooting

Facilitation Strategies

  • Iteration is a natural part of coding, and this Lab is designed so that students are intentionally put into a situation where they have to fix a problem. Pay particular attention to students who tend to struggle with perfectionist tendencies, or who do not do well with correcting their work in other subjects, and help them see that their success in this experience can be applied to other subject areas as well.
  • Use printables as manipulative to support project planning - See the printable resources available in the VEX Library, and use them with students as they are planning and building their Coder projects. You could use the motion planning sheets for students to draw the path they want their 123 Robot to travel, as well as the fill-in project and motion planning sheets for students to document their Coder cards and the path of the 123 Robot. You can also use the fill-in Coder sheet for students to write or draw their Coder cards to "save" their projects.
  • Use Coder card posters to reinforce learning with the Coder - Highlight specific Coder cards, or refer to cards as you are teaching with the Coder card posters. Students can use these posters to review terminology as they are working with VEX 123. See the Using Coder Cards Posters in the Classroom VEX Library article to access these printable posters and to see more strategies for using them in your learning environment.