Hi @jbn60 ,
Thanks for your interest in the NXP MIMXRT product, I would like to provide service for you.
I am the RT engineer, so mainly familiar with the RT situation.
Your side, also use the P3T1085UK sensor, you mentioned it is working, but when connect with the RT685, not working.
Do you do the correct configuration? Do you use ENTDAA or static address?
You also can refer to this application note for the I3C and the code to do the communication, whether that works or not? an12796, or the SDK code.
\SDK_2_14_0_MIMXRT685-AUD-EVK\boards\mimxrt685audevk\driver_examples\i3c
If still have issues, you can use the logic analyzer to check the I3C bus, where it is stopping.
Also check the data send to the sensor is correct or not.
Best Regards,
Kerry