Hi there,
Yea , those are cool, two way comms. But the Seeed Xiao Nrf52840 only act as a (NFC TAG) you get a reader near it, and it spits out , a www, or Ascii string, or WIFI credz, Which was the main purpose along with wwwās NO receive data possible. (it canāt read a TAG) 
The antenna allows it to answer.
HTH
GL 
PJ
we need a wow icon to click onā¦ cause sometimes a post just doesnt rise to the level of loveā¦
Since this topic is still recent, for those interested:
I managed to replicate Arduino Code on the Wiki using the āSeeed nRF52 mbed-enabled Boards Libraryā as stated and both antennas described in there (NFC Usage for both versions | Seeed Studio Wiki)
Hi there,
Looks Good , Start a new topic. It will be better.
the caps seem to make a fair bit of difference for the distance you get. Even the small antenna goes good with the right valuesā¦
GL PJ