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Internal Clock problem when switching from MKW21 to MKW22 MCU

Question asked by Matthieu Remacle on Nov 8, 2017
Latest reply on Dec 1, 2017 by Matthieu Remacle



Until now, I used MKW21D512VHA5 MCU for communication on 802.15.4 protocol. It works great. For supply reasons, I now have to use MKW22D512VHA5 MCU, which is basically the same but has a USB peripheral (that I won't use). Both processors are pin-compatible.


My problem is that since I switched from one processor to the other, I observe a massive difference in the frequency of the clock used as system clock (the clock frequency is 50% smaller with the MKW22 processor). This clock is generated from the low internal reference clock (low IRCLK).


The problem is that I can't communicate by UART anymore because of this behavior.


For both processors, the source code is exactly the same, the only difference is the SDK library that I built with MCUXpresso online tool. 


Here is a screen shot of my clock configuration (exactly the same configuration for both processors :




What are the difference between both processors ? Should I disable something linked with the USB peripheral in order to fix my bug ? 


Thank you for your help,


Best regards,