Hello Matthias,
The I2C interface of the NXQ1TXH5 is primarily intended to be used in combination with the NXQ1TXH5DB1355 debugging board.
You can read the chip temperature, Qi messages etc. using the commands shown in the UM11152.
The datasheet does not show how to read the registers of the NXQ1TXH5 as we do not support it.
Best regards,
Tomas