The Coder and Coder cards offer a screen-free method for coding the 123 Robot. This article will give you an overview of using the Coder.

Installing the batteries in the Coder


Use a small screwdriver to open the battery door on the back of the Coder, and install 2 AAA batteries. The batteries should last approximately 6 months before needing to be changed.

Note: VEX 123 Classroom Bundles include a screwdriver for opening and closing the battery door.

Turning on the Coder

To turn on the Coder, press the Start button. The indicator light at the top of the Coder will glow green to show that it is on.

Connecting the Coder and the 123 Robot

To connect, or pair, the Coder with the 123 Robot, both the Coder and 123 Robot should be turned on. Push the 123 Robot along a surface to “wake” it, and press the Start button on the Coder to turn it on. Listen to the following animation to hear the 123 Robot "wake."


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.

The indicator lights will show yellow on the top of the Coder and the 123 Robot. Release the buttons to begin the pairing process. The process is complete when the 123 Robot makes the connected sound and pulses white, and the indicator light on the top of the Coder flashes green. Listen to the following animation to hear the connection sound.

The Coder will remember and automatically reconnect to the last 123 Robot used. When the Coder finds the previously connected 123 Robot, it will automatically reconnect and the 123 Robot will make the connected sound. Listen to the following animation to hear the connection sound.

To connect the Coder to a different 123 Robot, repeat the connection process again with a different 123 Robot.

Note: When connected to the Coder, the 123 Robot will not time out, but will stay on until the Coder is turned off, or the 123 Robot itself is turned off.

Using the Coder


The VEX 123 Coder can be used to create projects to bring your 123 Robot to life with code. The Coder cards are used to build projects with the Coder.


A project must always begin with the When Start 123 Coder card in the uppermost slot, marked with a white arrow.

Insert Coder cards from the right hand side, by sliding them into a Coder slot under the protective cover.

The protective cover can also be removed by sliding it to the right. When replacing the cover on the coder, the protective cover must be inserted into the grooves on the top and bottom of the Coder before being snapping into place. Listen to the following animation to hear the protective cover snap into place.

To continue to build a project with the Coder, slide additional Coder cards into the numbered slots. The Coder will read the project from top to bottom. For more information about what each Coder card does, see the Coder card Reference Guide.

To change a project, remove or reorder the Coder cards by sliding them out of the slot and reinserting them in the desired location.

Note: You should only change Coder cards in a project when the 123 Robot has stopped running the project. Do not manipulate Coder cards while a project is in progress.

For more information about Coding with the Coder and Coder cards, view the Coder and Coder Cards section in the VEX Library.

Starting your Coder project


With the 123 Robot and Coder connected, press the Start button to start your project on the 123 Robot.

When you press the Start button, the indicator lights to the left of each Coder card slot will flash in sequence, as the Coder reads each Coder card in the project.

If any Coder card slot does not show green, see the Troubleshooting the Coder VEX Library Article for more information.

You will hear the 123 Robot play the start sound when it begins the project. As each Coder card is read, the indicator light beside that Coder card will show green. When the project is completed, the 123 Robot will play the completed sound. Listen to the following animation to hear the start and completion sounds.

To start your project again, or change your project and start a different one, remove or replace the Coder cards as needed, and press Start again.

Stopping a Coder project while it is running


Press the Stop button to cause the 123 Robot to stop a project at any time.

When the Stop button is pressed, the indicator light on the top of the Coder will show red. The 123 Robot will stop its action, and the indicator lights beside the Coder card slots will turn off.

Using the Step button on the Coder


Stepping allows you to individually step through a Coder project. Normally, when a Coder project is running, it moves on from one card to the next as soon as that action is completed. Using the Step feature, you can start a project, but in a special mode where you control the flow. When using the Step button, the 123 Robot will pause after each Coder card, until the Step button is pressed again.

Stepping can be useful to make the connection between the behaviors of the 123 Robot and the individual Coder cards, and troubleshooting or debugging a project. To learn more about stepping through a project with the Coder see the VEX Library article.

Turning off the Coder

To turn off the Coder, press and hold the Stop button until the indicator light at the top of the Coder turns off.

Turning off the Coder will also turn off the connected 123 Robot. Turning off the connected 123 Robot will also turn off the Coder.

For more information, help, and tips, check out the many resources at VEX Professional Development Plus

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