I'm developing a custom board with nRF52832. We developed a flexible circuit for NFC antenna, and tuned following the indications on this post on the Nordic blog. Actually, I changed some capacitors to maximize the NFC pins voltage.
Firmware is based on the NFC example "record_url" on SDK11.0.0, library "nfc_t2t_lib_gcc.a", so very simple. We are using S332 0.9.2 (ANT + BLE), and FreeRTOS.
When the smartphone goes near the antenna, the voltage on NFC pins is over 3Vpkpk, but communication is very difficult. I can see the amplitude modulation, seems ok.
Could it be something related to hardware, like Q of antenna (when I developed a RFID reader for Mifare tags, Q was critical for good communication)?
What can I check via firmware? Some registers value? Should I re-init NFC after the smartphone has gone?
Thanks a lot!
Andrea