Having issues with the ST25R3916

[CBerr.2]

ST25R3916 is having issues, pointing to a layout issue but hoping for some insight also on the schematic (both attached).

Have broken our board out and running the ST25R dev kit via SPI with our STM32 no problem pointing to issues with the ST25R.

Pursuing layout issues "grounding/current loops" causing a potential brown out of the ST25. Any thoughts on schematic or layout would be great.

[CBerr.2]

Looks like our issue is related to running the IO off 3v3 and the VDD_TX/VDD off 5v0.

Is there any particular start up sequence for that use case?

[Ulysses HERNIOSUS · Accepted solution]

Hi,

there are no special start up procedures required for your mentioned use case.

Before diving into details of schematic and layout let us first clarify what exactly you see...

• What makes you think that there is a brown-out / voltage drop? Did you observe it on any lines?
• During which operating condition do you observe this? What is SW doing in this case?
• What do you refer as ST25R dev kit? ST25R3916-DISCO or X-NUCLEO-NFC06A1?
• Please go in small steps to verify your board. Proposed steps are (similar to selftest feature of newer RFAL)

1. Verify the voltages with a scope
   1. Verify register read - e.g. IC Identity register
   2. Verify register write - e.g. write and read back the bitrate register
   3. Verify operation of oscillator/crystal - on setting 'en' bit the INT line should go high and software should handle the INT in its ISR, also osc_ok bit should be set.
   4. Turn on the field by setting 'tx_en' bit.
   5. Verify again the voltages using a scope.

Regards, Ulysses