Serial sensor change state after data has been read

Hello, I am trying to figure out how to change my state back to an untriggered state after my motion sensor has been triggered.
I am currently using the serial sensor platform configuration to read the data arriving to my usb port (my device is a bbc microbit with motion sensor) it works and changes the state to show the data (e.g motion has been triggered) but it will stay at that state forever and I have no way to tell if motion has been triggered again.
I want to do something like, change state to no motion detected after 30 seconds, to stop my state always displaying motion detected.

Currently code I am using is :

#configuration.yaml
sensor:
  - platform: serial
    serial_port: /dev/serial/by-id/usb-ARM_BBC_micro:bit_CMSIS-DAP_9901000051864e45003d1008000000240000000097969901-if01
    baudrate: 115200

I then just then impliment Glance card configuration from lovelace and it shows the data on the frontend.
I think I need to use an automation trigger but I’m unsure how to implement a state change after a certain amount of time.
Sorry if this is a stupid question, I am completely new with home assistant and unsure how to do the task.
Any help would be greatly appreciated, thanks for your time.

Add a value template to your sensor to look for the unique string that identifies motion. At the moment it’s just registering movement when anything is received on the port.

What is the serial output of the microbit when there is motion, and when there is no motion?