Read value from knx motion detector

How to I define the item that should read the output of a KNX motion detector?

I’ve tried to use the following item definition, but the logs doesn’t show the value.

Switch Motion_GroundFloor_Living_Stairs "Motion is [%d]" {knx="<0/2/21"}

What is the dpt of 0/2/21?

I’ve configured ETS in such a way that the motion detector sends a binary message to address 0/2/21 when it detects a motion. An off signal is send after the staircase function.

The configuration seems to be correct. Is the connection between openHAB and knx working, i.e. do you have other items in openHAB with knx binding which work as expected?

I am using somethink like that
Switch PM_EG_Wohnen “Motion [MAP(]” {knx="<4/2/0"} is the mapping for ON = active and OFF = inactive