Failed to write command, err_code = 33281；Failed while calling TWI tx 1

[yoyou]

HI,

i using 52840DK SDK17.2 s140 10056 test NFC pairing.

ble_central\experimental\ble_nfc_pairing_reference_c 10056 s140
ble_peripheral\experimental\ble_nfc_pairing_reference 10056 s140

the peripheral NFC tag can be found by android phone.
but central ble_nfc_pairing_reference_c， i got error like as follow pic:

Failed while calling TWI tx 1, err_code = 33281

Failed to write command, err_code = 33281
my question is，how to solve the error? 
thanks for help.

[Kenneth]

Hello,

Error code 33281 is 0x8001, and looking at sdk_errors.h I can find:
NRF_ERROR_DRV_TWI_ERR_ANACK

This is due to NACK received after sending the address:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/twim.html#register.ERRORSRC 

Basically this means that the slave did not respond to the serial address, either caused by no pull-ups on the TWI pins or that the address is wrong. 

I suggest to run the twi_scanner example project to find the address of the sensor:
https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/twi_scanner_example.html 

Kenneth

[yoyou]

thank you very much,

i run the twi_scanner example project ,No device was found.

and ble_nfc_pairing_reference config as follows right，freedom from error log.

Two NFC antennas are close together，the peripheral NFC tag can be found by android phone.but twi_scanner can't.

[Kenneth]

I think the next step now is get a logic analyzer so you can observe the twi pins (clk and data), I think we are missing something here (wrong pins, missing pull-ups etc).

Kenneth

[yoyou]

thaks for your help