xbp24c don't hear anything from AT86RF233

Hello,

I’m using an xbp24C to listen to an AT86RF233 ( http://www.microchip.com/wwwproducts/en/AT86RF233 ) but I don’t succeed.
I tried with a CC2531 ( http://www.ti.com/tool/CC2531EMK ) in place of the xbp24C and it works “out of the box”. Here’s a screenshot of some packets. https://img42.com/auwZZ

Using xctu, I set panId to 0xFFFF and scan channels to 1 ( I know these parameters are correct, I can see them in CC2531 GUI ).

What else should I do or look out?

Regards
Julien