CIR buffer zeros for "Tag Final" message in TWR

Hi All,

I am using TREK1000 (DW1000) to record CIR. I modified the TWR application in the TREK1000 and I can record good CIR for TAG POLLING message and ANCHOR REPONSE message. However, the CIR of the TAG FINAL message contains all zeros. I will appreciate very very much for any help/suggestion. (I’m quite new to UWB too)