MySQL "Before insert" trigger stops insertion process

[Hamsavardhini Deventhiran]

Intro:-
I have one sensors which is writing its processed data into an MySQL database.

Since the scanning process is every 40seconds, my data grows huge.

So I decided to prevent my sensor to write some unwanted data using triggers.

Issue:-
But the thing is, If any such row satisfies violates the condition, mysql trigger throws exception and prevent my sensor from writing data.

From the time I executed my the trigger till I deleted it, there is no data written by sensor. As soon as I dropped my trigger, data started to flow in.

My Expectation:-
I want to write a logic to an mysql table which should not allow insertion of a record, lets say if a column value is "A" and insertion process should continue.