NTP5312 Event Detection pin staying ON (low) Hello all, I'm struggling with NTP5312 event detection configuration. I have configured it to be in NDEF message TLV length mode (6). When I write a NDEF message from my phone, the pin goes low, I can generate an interrupt in my MCU and read it. But the pin stays low, even after the NFC field (phone) is removed. But according to AN11203, the pin behavior should be: • ED=ON: when Block 1 byte 1 i.e. NDEF length byte is non-zero during write command. • either: – ED=OFF when Block 1 byte 1 i.e. NDEF length byte is zero during write command – NFC Field is OFF. I tried to clear the pin by writing 1 to the lowest bit of 0x10AB but that did not have any effect. Only power cycle restores its state. How do I clear ED pin to prepare for the next NFC write event? Re: NTP5312 Event Detection pin staying ON (low) I'm not continuously transferring data; my use case is configuring the device by transferring configuration data over NFC - for example, as NDEF message containing a JSON object. I also have SRAM mirroring enabled to avoid writing to EEPROM. The first time after the power cycle works - I catch the interrupt and read the message. But I can't reset the ED pin state. I tried writing back zeroes over I2C bus - but it had no effect, ED pin stays low. The idea is: 1. NFC write occurs, ED pin goes low 2. MCU catches the interrupt, reads NDEF message and processes it. 3. MCU somehow resets ED pin back to HIGH to prepare for the next write (these writes are occasional, whenever there's a need to update the configuration). I'm stuck at step 3. The ED mode is NdefTlvLength, I tried writing 01h to ED_INTR_ CLEAR_REG and tried filling the SRAM with zeroes, erasing the message. Both failed, ED pin stays LOW. How else could I make NTP5312 release its ED pin? Re: NTP5312 Event Detection pin staying ON (low) Hi @azarubkin
Hope you are doing well.
I apologize for the confusion this may cause; with this configuration, ED pin state will change depending solely on ZERO/NON-ZERO Length byte.
Could you please provide a few more details on what you are trying to achieve? If you are constantly transferring data, is the NTAG 5 - Bidirectional data exchange approach useful for you?
Regards, Eduardo. Re: NTP5312 Event Detection pin staying ON (low) Hi,
In this configuration, ED pin should be released by writing 00h to Block 1 Byte 1.
Regards, Eduardo. Re: NTP5312 Event Detection pin staying ON (low) That is what I thought, but it didn't work for me. I tried writing an empty NDEF message with zero length, or zeroing out the whole 256 bytes of SRAM, but the ED pin stays high. I tried doing this from I2C side - should it work, or did you mean writing from NFC side? Re: NTP5312 Event Detection pin staying ON (low) Hi,
I tried using OM2NTP5332, configuring ED pin for NDEF TLV length, and then alternate Block 1 Byte 1 between 00h and e.g. 10h by using NTAG 5 Cockpit (I2C):
Screenshot 2026-03-11 172653.png
When this byte is 00h, ED pin is OFF; when this byte is different than 00h (10h in this example). ED pin is ON.
Regards, Eduardo. Re: NTP5312 Event Detection pin staying ON (low) Hi @azarubkin and @EduardoZamora , I am facing the same issue with the NTP5312. First, I configure register 0x103D with the values 0x79 0x00 0x01 0x00 (enable NFC field detection). When I read back the register, it correctly returns 0x79 0x00 0x01 0x00. My other register configurations are: 0x1037: [0]: 0x09; [1]: 0x00; [2]: 0xFF; [3]: 0x00 (other configurations are set with passwords) The ED pin is connected to a GPIO configured as an input, and I have an external pull-up resistor connected to the ED line. Others registers configurations: 0x1037: [0]: 0x09; [1]: 0x00; [2]: 0xff; [3]: 0x00 (others configs with passwords) I have the ED pin connected to GPIO pin configured as input. I also have a pull-up resistor connected to ED pin. The first time an NFC field is detected, the ED pin goes from HIGH to LOW and the interrupt is correctly generated. However, when I then try to read register 0x10AB, I get 0xFF 0xFF 0xFF 0xFF. Furthermore, when I attempt to write 0x01 0x00 0x00 0x00 to 0x10AB to clear the interrupt, I get a write error. Any insights on why these registers are returning 0xFF or failing to write? Could you try to replicate this setup on your end to confirm if you get the same error when accessing register 0x10AB? Regards, GS Re: NTP5312 Event Detection pin staying ON (low) Thank you. I decided to use a workaround: I switched ED mode to WriteSynchBlock, the synch block number is 2 (1 may work too, I'm not sure). That way I get an interrupt when NDEF message is written and the pin is released by explicit ED clear command. I've read the user manual for NTAG 5 Cockpit, and it mentions that the hardware used to build the reference setup is the assembly of [LPC11U37H LPCXpresso board] acting as USB-I2C bridge I'm not sure if we have LPC11U37H LPCXpresso board. Would it be possible to use a different USB-I2C hardware? Re: NTP5312 Event Detection pin staying ON (low) Hi @EduardoZamora , Can you help me with my issue? Thanks! Regards, GS
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