MKL17 uart dont`t work at low temp and when at room temperature to work properly. Why?
What exactly is 'Low'?
What is the clock source as that is the most temperature dependent component?
If you're running from the internal clock reference, check the frequency drift vs. temperature curve in the datasheet. Looks like it varies by maybe 0.5% over 20 degrees C, which could be enough to take your baud rate out of spec.
The one time I've gotten a crystal-referenced MCU enough out of spec to be a problem, I had it at about -190 C, just above the liquid level in a dewar of liquid nitrogen.
On the other hand, the first time I used Processor Expert for clock setup I accidentally selected the internal reference instead of external. My first prototype worked OK but without trimming it was hit or miss on the others.
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