How do I pass data from a reader to the I2C port?

[DJack.8]

I have a need for short range communication with a very low data rate (4 bytes updated at 2Hz). The application is constrained by size and power. The device is a set of actuators that are to be controlled by a small microcontroller. The 4 bytes contain the data for the actuators.

My idea was to use a ST25DV04K tag connected by I2C to a microcontroller. I would then pass data from the reader to the tag and then on to the microcontroller for it to operate the actuator. I am uncertain as to how the data would be passed to the microcontroller. Can the ST25DV04V pass data from the reader directly to the I2C port? Or, would I need to write data to memory in the tag and have the microcontroller poll/read the memory.

Is there problem with my concept or is there an easier solution?  Is there an app note or example for something similar? The microcontroller side of the device needs to be simple, small, and low power. For example, I could not use a NFC reader device on the microcontroller end. 

Thanks,

Doug

[JL. Lebon · Accepted solution]

​Hello,

The ST25DV04K has a feature called "Fast Transfer Mode" which is designed for data transfet between the RF reader and the I2C master (in both direction). I think is what you ate looking for.

In this mode the reader can write data in the ST25DV's SRAM buffer though RF interface, and then the microcontroller can read this data in SRAM buffer though the I2C interface.  The Fast Transfer Mode provides all signaling and status bytes to help the synchronization of the two interfaces (i.e. the MCU can be waken-up by an interruption when the reader write or read a message in the SRAM)

It is a better solution than using the EEPROM memory to transfer data from reader to MCU since there is no memory cycling issue and the write time is much faster.

The fast transfer mode is explained in the datasheet, and you can also look at the application note AN4910.

There is also code example of Fast Transfer Mode SW and FW implementation provided with the ST25DV discovery kit and in the ST25 android and iOS application source code.

Best regards.

[DJack.8]

Thanks JL,

That tells me what I need to know. I'll purchase the kits and give this a try.

Doug