Hello Hancheng,
From the schematic of FRDM-K64 , configure the PTB21 to low(0) , the blue LED
can be light , use this code :
GPIO_ClearPinsOutput(BOARD_LED_BLUE_GPIO,1<<BOARD_LED_BLUE_GPIO_PIN);
while in your code , you set this pin to high (1) :

So please change it ,then your project can work well .
Hope it helps !
Have a great day,
Alice Yang
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