I_OSC raised unexpectedly during Wake Up mode

LltWc · ‎2025-01-24

I've been implementing Wake Up mode with inductive wakeup on the ST25R3916 with custom firmware. It's all functioning as expected, except for the oscillator interrupt.

As seen in the logs below, when I switch to Wake Up mode, I mask every IRQ except I_WAM and I_WPH. Just to be safe, I added a readout. The Wake Up timer is configured to take a measurement every 100ms. But every 100ms, it sends an I_OSC interrupt when it switches to Ready to take amplitude and phase measurements. Why would this occur? Is there something beyond just M_OSC being set that I need to do?

Brian TIDAL · ‎2025-01-24

Hi,

as explained in §4.2.5 Wake-up mode of the ST25R3916 datasheet, the reader field is activated for an extremely short time to allow phase or amplitude measurements during wake-up mode. Thus, the oscillator is enabled during this short time and I_osc is triggered when the oscillator is stable.

This is a normal behavior.

Rgds

BT

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