NFC on nRF52832 doesn't work if HAL_NFC_FIELD_TIMER_PERIOD is set to maximum value.

[Michal]

NFC examaples in SDK 12.2 and 13.0.0-1.alpha on nRF52832 (board PCA10040) may not work if HAL_NFC_FIELD_TIMER_PERIOD is set to a value higher than 255. HAL_NFC_FIELD_TIMER_PERIOD is defined in sdk_config.h. Documentation says it can be set to the values: 100 .. 10000. Default is 100.

[Michal]

The reason is, hal_nfc_t2t and hal_nfc_t4t use NFC field timer (TIMER4) in 8-bit mode. The solution is to use values 100 .. 255 for HAL_NFC_FIELD_TIMER_PERIOD in sdk_config.h or change NRF_TIMER4->BITMODE to 16-bit in hal_nfc_t2t.c (line 158) and in hal_nfc_t4t.c (line 173)