debugging ST25R3911B loss of sense range

[anotherandrew]

I'm picking up a design from another engineer, and we've noticed the most recent hardware revision of our board has a sense range of approximately half of the previous version. We're using the same antenna and matching network, same layout and components. There is a minor change in the stackup which I'm not discounting, but I'd like to find out if the 3911 has debug facilities that would help me see what it's struggling with.

What facilities does the 3911 have to diagnose read issues? I see that it has some trim pins that it presumably uses to try to maximize the power transfer, does it have any registers I can access to see if it's running out of headroom trying to read the tag? Are there any app notes or diagnostic routines I can read?

[Ulysses HERNIOSUS · Accepted solution]

Hi andrew-st,

for measuring antennas and matching I recommend to study AN4974.

Chip internally you cannot directly diagnose read issues. But by using internal ADC and comparing values against values from the previous board you may get some hints. We are sometimes using it to perform board testing at manufacturing site - see if we still see the same voltage supply, regulated voltage, amplitude and phase on RFI.

However this can only ensure that matching and antenna is the same. Read range could also be influenced by noise on the board, etc.

So for ensuring the receive path we are also falling back to styrofoam brick with a tag on it which needs to be readable in a defined good distance.

Best Regards, Ulysses