Cannot calibrate antenna on ST25R3911B

[IMolt.1]

I'm trying to issue the CALIBRATE_ANTENNA (0xd8) command on my st25r3911b nucleo expansion board, but it seems to hang.

Other commands (eg. MEASURE_CAPACITANCE and CALIBRATECAPACTIVE_SENSOR) work just fine and generate interrupts, but issuing CALIBRATE_ANTENNA literally just does nothing as far as I can see.

What am I missing ?