XIAO NRF52 NFC tuning

I am trying to match an an Antenna to an NRF52840. I tried to use the formula described in the “nRF52832 NFC Antenna Tuning nWP-026” White paper from Nordic. I connect the nanovna to a coil 6.8nH and another coil (also 6.8nH) to the nrf52840 XIAO. I measure the resonance at 1.7 MHz. With that I can calculate the internal capacity of the board which is 1.271 nF. In the document it is described as 4pF. How should I proceed?

Hi there,
So the Nrf52840-DK comes with a little NFC antenna (I posted a Pic of it, somewhere on here :face_with_peeking_eye:) and maybe take a look at the schematic and see if the values compute to what you have and compare the component values.
check some threads on here too, some have got it going if I recall. “NFC Antenna” or “nrf52840 NFC” is my .02
GL :slight_smile: PJ

Found it,

and diagram.