nfc uart poller is not working

[weizhen]

I am working on the nfc uart examples. first I found the poller example is not support for 10056 board. I make the change for that. code can build and flashed, but then I received the error code 

<error> app: ERROR 33281 [NRF_ERROR_DRV_TWI_ERR_ANACK] at ../../../main.c:300

PC at: 0x000045BB

<error> app: End of error report

it happened on adafruit_pn532_init

Do you know what's wrong with the example? and how to fix that?

[Karl Ylvisaker]

Hello,

Could you specify exactly which example you have modified to work with the nRF52840 DK?
The NRF_ERROR_DRV_TWI_ERR_ANACK error means that the TWI slave has not acknowledged the TWI transfer. This could be a result of an erronus connection between the two devices, or if there is anything preventing the TWI slave from receiving/acknowledging the transfer.

Please note that the nRF52840 DK does not have a PN532 on board, and so you would have to connect this module externally.
Could you detail how this connection is made? Preferably with a connection diagram where you note which pins are connected to which pin on the opposing device.

Best regards,
Karl