NFC antenna interface on the nRF52840 DK

The nRF52840 DK supports a Near Field Communication (NFC) tag.

NFC-A listen mode operation is supported on the nRF52840 System on Chip (SoC). The NFC antenna input is available on connector J5 on the nRF52840 DK.

Figure 1. NFC antenna connector

NFC antenna connector on the nRF52840 DK

NFC uses two pins, L24 (NFC1) and J24 (NFC2), to connect the antenna. These pins are shared with GPIOs (P0.09 and P0.10) and the PROTECT field in the NFCPINS register in UICR defines the usage of these pins and their protection level against abnormal voltages. The content of the NFCPINS register is reloaded at every reset.

Note: The NFC pins are enabled by default.

NFC can be disabled and GPIOs enabled by defining the CONFIG_NFCT_PINS_AS_GPIOS variable in the project settings. The way of doing this depends on the Integrated Development Environment (IDE)/toolchain in use:

When using SEGGER Embedded Studio, select Project > Edit Options > Code > Preprocessor > Preprocessor Definitions and add the CONFIG_NFCT_PINS_AS_GPIOS variable.
When using Keil, go to Project > Options for Target > C/C++ > Preprocessor Symbols > Define and add the CONFIG_NFCT_PINS_AS_GPIOS variable.

Pins L24 and J24 are by default configured to use the NFC antenna, but if they are needed as normal GPIOs, R44 and R46 must be NC and R43 and R45 must be shorted by 0R.

Figure 2. NFC input