NFC Tag (ST25DV04KC) GPO Reset

[Sumukha1]

We’re facing an issue with the ST25DV04KC tag. The tag is powered through energy harvesting. The GPO register unexpectedly resets to 00 whenever there’s a brief drop or interruption in the RF field or Communication. The GPO is configured to generate an interrupt when the tag enters an RF field, this interrupt is what signals the host device (via I²C) to initiate communication. When the GPO register resets, no interrupt is generated, so the host device can’t detect the RF field and communication never starts.
As far as we know, the GPO register is a static register and should retain its configuration. Even after locking the configuration registers, the reset still occurs.
Could you confirm if this is expected behavior, or if there’s a known workaround to maintain GPO configuration across short RF power losses or Communication drops?

[JL. Lebon]

Hello, 

As you have understood, the GPO is a static configuration byte. It is stored into an EEPROM. If it is written to a certain value, this value is retained across power off/on cycles. RF field interruptions do not change its value.

Can you explain in more detail how you program this register and how you read it to see it is changed to 00?

Best regards.