NT3H2111 FD Pin

[dt_t]

Hi Team

1) I set FDOn= 00b and FDOff= 00b in NC register of the session bytes of NT3H2111 to catch the RF present or not event. However, I can observe some bouncing signal on FD pin, as attached, when I put a phone near to the NFC antenna. Would you help how to solve the bouncing signal on FD pin? Any register settings in the NT3H2111 can help to solve this problem?

2) If the NT3H2111 set to use pass-through,

( i) Will the FD pin go low if a phone put near to the NT3H2111 to read the tag data? 

( ii) Will the FD pin go low if a phone put near to the NT3H2111 to write data to the NT3H2111? 

3) Is there another way except using the pass-through method to acknowledge the microcontroller to read the tag data if a phone put near to write data to the NT3H2111?

Thanks

dt

[nxf58474]

Hi dt.t,

Hope you are doing well. Are you using a Pull-Up Resistor? Please see the Figure 12 of the Data Sheet.

Regarding your second question, please see this Application Note, in section 4.1 and 4.2, is the explanation of a Data Transfer from NFC to I2C and from I2C to NFC respectively. The Communication scheme would be really helpful.

The Field Detection Pin can be configured to react in the following ways:

So, if you need your MCU knows when your phone writes to the tag, it is necessary to use the Pass-Through Mode.

Hope this helps. If you have any question please let me know.

Best Regards,

Ricardo Zamora

[dt_t]

Hi Ricardo

Response to your question, I put a 12k pull-up resistor on FD pin. Is it appropriate?

Is the bouncing signal related to the improper matching of the NFC antenna?

Can I put a capacitor on FD pin to the GND to improve the bouncing signal problem? If yes, what values would you advise?

Thanks

dt

[MrMax]

I think the signal is bouncing because the phone is in the near proximity, this is natural and the signal will be stable once you have enough field strength.

You have to debounce the signal in your end with software, as you should do with all noisy signals, such as switches and buttons.

[dt_t]

Hi Ricardo

I have a question about pass-through.

Conditions: PTHRU_ON_OFF= 1b, FD_ON= 11b, FD_OFF=11b, TRANSFER_DIR= 1b( NFC->I2C)

Does SRAM_I2C_READY set to 1 if NFC try to write data( not longer than 30 bytes) to NT3H2111?

How does microcontroller know the data in SRAM is ready when NFC finish to write the data( not longer than 30 bytes) to the tag?

Best Regards

dt

[nxf58474]

Hi dt.t,

Yes, that resistor is good. A capacitor should not be necessary.

There are two commands: the WRITE command (4 bytes), and the FAST_WRITE command (the 64 bytes of the SRAM). Please refer to the section 4.1 of the Application Note.

The ways the MCU can know the data is ready to be read are:

• The host polls/reads bit SRAM_I2C_READY from NS_REG to know if data is ready in SRAM
• A trigger on the FD pin indicates to the host that data is ready to be read from SRAM.

Best Regards,

Ricardo