(Connection events) LLID empty PDU, can I answer with a valid data? How?

Hello, there is a way of send on every connection events an answer with valid data?
I have a project with CC2541 with a latency 4 on a interval connection by 500ms... so, I have a valid communication every 2,5s.
My question: how can I get the LLID and detect a empty PDU to insert in a answer of a connection events my data?

Best regards!