I tried voltage level shitfter but it does not work. I think problem is GPIO14 and GPIO15. Because when I changed uart pin as GPIO14 and GPIO15 and upload code in RSL10 EVB, it does not work also. GPIO14 and GPIO15 are JTAG pins. By making some arrangement, I can use them as normal DIO according to KB: How to enable DIO13,DIO14 and DIO15 for normal DIO function? topic.
Do you have idea about that ? I checked these two pins by oscilloscope, I can not control them. I could not make high or low these two pins.
Edit: I tried a lot of things to make UART pin GPIO14 and GPIO15 but it did not work. This code only works with GPIO4 and GPIO5 even if I made every adjustment at code. Although I changed UART pins, it always tries to communicate with GPIO4 and GPIO5. Do you know why is that ?
Thanks a lot.