ST25R3911B NFC reader without Crystal

[Creemers]

Hi, we are using an ST25R3911B NFC reader. Is it possible to drive this chip without a crystal, and use a generated clock source instead (coming from an MCU)?

We found the following article on your forum: https://community.st.com/t5/st25-nfc-rfid-tags-and-readers/is-it-possible-to-use-a-clock-oscillator-instead-of-quartz/td-p/301081, but for some reason we are not getting it to work. The input clock we use looks OK when using a oscilloscope. We configured the tana_7, as well as the OSC bit, but is seems not to give an analog field (but we are able to communicate to the reader over SPI).

If this is possible, what is the moment that these registers need to be configured?

[Ulysses HERNIOSUS · Accepted solution]

Hi Creemers,

Register access is independent of oscillator. To my knowledge no special sequence is required. Please also set 'en' bit and observe 'osc_ok' bit. Furthermore you should be able to observe the 3.4MHz on pin MCU_CLK(depending on 'out_cl' settings).

BR Ulysses