Hi Antoni Torne,
If other slave MCU can work with your master, I think the main problem of your KE SPI is caused by your SPI slave code.
Please download the KExx driver, you can find the SPI slave project which works in the interrupt mode.
The download link is:
FRDM-KEXX Driver Library Package
You can find the SPI slave code in folder: KEXX_DRIVERS_V1.2.1_DEVD\kexx_drv_lib\build\iar\ke02\SPI_Slave_demo
Please refer to the official demo code to check your own code.
Wish it helps you!
If you still have problem, just let me know!
Have a great day,
Kerry
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