Hi Ajinkya J,
From your problem description, I think your UART0 receive configuration may have problem.
Actually, we have some uart0 sample code for FRDM-KL25, please download it from this link:
http://cache.nxp.com/files/32bit/software/KL25_SC.exe?fpsp=1&WT_TYPE=Lab%20and%20Test%20Software&WT_...
After you install it, you can find the uart0 code in the folder:
KL25 Sample Code\kl25_sc_rev10\klxx-sc-baremetal\build\iar\platinum
This code will send the received char data back to the uart0.
Wish it helps you!
If you still have question, please contact with me!
Have a great day,
Jingjing
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