TimeFilter combined from Date and Time

I have a DB and there is no DATETIME datatype only a DATE and TIME as separate column.

Now I tried to combine those two with the mysql TIMESTAMP function like:

TIMESTAMP(opDate, opTime)

resulting in this querry which does not work:

SELECT
TIMESTAMP(opDate, opTime) AS “time”,
Temperature,
Humidity,
WindDirection,
WindVelocity
FROM daten
WHERE
time BETWEEN __timeFrom(TIMESTAMP(opDate, opTime)) and __timeTo(TIMESTAMP(opDate, opTime))
ORDER BY TIMESTAMP(opDate, opTime)

any hint or idea how to fix it?

Andy