st25dv64kc FTM transfers to android reference app.

[MBrog.2]

Hello. I'm trying to use the st25dv64kc with FTM and energy harvesting and a modified version of the reference ST android application. According to the scope it appears that power is available from the energy harvesting, but there seems to be a pinging sequence occurring from the android side which makes a continued connection to the NFC chip difficult to maintain. Are there any features in the ST android SDK to help with maintaining a connection to the NFC chip or any best practices for maintaining FTM transfers while energy harvesting?

Thanks!

[JL. Lebon · Accepted solution]

Hello, 

From what I understand, you have an oscilloscope connected to the Energy harvesting pin, so you can check the voltage delivered. What is the voltage you observe? Is this voltage constant or is it dropping sometimes?

If voltage is dropping to 0V, there can be several explanations: the phone or the tag is moving, de-aligning the antennas. Or may be your MCU or other devies that are powered by EH are drawing too much peak current. Or maybe the phone is cutting the RF field (this happens mainly on iPhones, not on Android phones usually).
You can check the RF field produced by the phone with a scope, by making a one-loop antenna with a simple wire, connected to your scope and that you place between the tag and the phone. This is a simple way to observe the RF field.

Also, in order to do FTM, you should have a microcontroller connected to the ST25DV, I guess it is also powered by the energy harvesting? What kind of microcontroller do you use? EH can deliver only small power and only Ultra Low Power MCUs can run on it.

Best regards.