Digital Twin of the LED Light. Referencing in UE5

Referencing allows for communication between blueprints, the sender and the receiver.


To enable communication between two Blueprints in Unreal Engine — for example, a sender (like a serial communication Blueprint) and a receiver (such as a Spotlight Blueprint) — I followed the steps below:

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1. I saved both Blueprints in the same directory to ensure that one could easily reference the other.
2. I placed both Blueprints in the World View by dragging the sender and receiver Blueprints into the level so they existed as instances in the world.
3. Next, I created a reference variable in the Sender Blueprint (the one responsible for sending data).
   In the Variables panel, I clicked the + icon to create a new variable and changed its type to the class of my Receiver Blueprint (for example, BP_Spotlight).
   I named this variable ReceiverRef to keep it meaningful.
4. After that, I made the variable editable.
   With the variable selected, I went to the Details panel and checked Instance Editable (the small eye icon appeared next to the variable name).
   This allowed me to assign a reference to the variable directly from the Level Editor.
5. In the level, I selected the Sender Blueprint instance and, in the Details panel, found my editable variable under the Default section.
   I then used the dropdown menu to assign the Receiver Blueprint instance (for example, the Spotlight Blueprint) that I had placed in the world.
6. Finally, inside the Sender Blueprint, I dragged the ReceiverRef variable into the Event Graph and used it to call functions, set variables, and trigger events in the Receiver Blueprint.
   

Resources:

Potentiometer hookup: How to Use a Potentiometer with Arduino analogRead (Lesson #7)
Serial Communciation arudino: Arduino to Unreal Engine Serial Communication


Summary:

So basically, I have creates 2 blueprints. The first one handles serial port communication. 1^st the serial communication plugin that I outsourced from GitHub, but then I’ve modified it. I created a custom event that reads data coming from the Arduino as strings, converts those strings into floats, and then maps the range of values (from 0–255 on the Arduino side) to a new range of 0–100,000 in Unreal Engine. This mapped value represents the light intensity inside Unreal.

Using that data, I update the light’s intensity in real time, making the digital twin of a red LED in Unreal Engine. I managed to get the two blueprints communicating with each other by referencing the red light blueprint inside the serial communication blueprint.

Next steps:

Now, I’m going to be working on a new blueprint for the character animation. I will be working with Unreal state machine and transition state that will be initialised with Arduino data. I want to use the Arduino data again to control this transition — for example, switching from idle to walking when the input value crosses a threshold.

Let’s say if the Arduino’s light intensity value is greater than 100, I want the character to transition from idle to walking. In other words, the character’s animation changes dynamically based on the real-time Arduino input, reflecting user interaction and sensor data in the scene. This will be a real-time interaction of predefined animation states.