Need tag custom reply ATQA /SAK, Is this operation supported？
Yes, it does support this operation. I checked with experts regarding this and here is a brief explanation on how to change it. The solution depends on the for the frame you needs to customize:
ATQA - use nfc_t4t_parameter_set() function to set the desired NFCID1 (UID); as of Bit Frame SDD, we don't provide an API to modify it, so you will need to set it directly in the nrfx_nfct.c driver source code: line 158 in function nrfx_nfct_hw_init_setup(): modify nrf_nfct_sensres_bit_frame_sdd_set(NRF_NFCT_SENSRES_BIT_FRAME_SDD_00100); You can change to a desired bit frame SDD value. Changing other bits in ATQA doesn't make sense - we shouldn't declare the Type 1 Tag support.
SAK - depends on which tag library is used:
Type 2 Tag: set the desired SAK value using: nrfx_nfct_parameter_set(), call it before nfc_t4t_emulation_start()
Type 4 Tag: use nfc_t4t_parameter_set with NFC_T4T_PARAM_SELRES parameter, call it before nfc_t4t_emulation_start()
