Lattepanda initializing problem

Hello,
I am trying serial communication between UART port (for Intel CPU) and arduino leonardo. (and I am using level converter)
After wiring between of them, I uploaded below code to leonardo.

void setup() {
Serial1.begin(9600);
}

void loop() {
}

But, Some problem occur.
If I shut down the Lattepanda and press power button, red led (indicating Lattepanda initialization) is turned on.
But, after some second, red led light is weaken a little and display panel doesn't show anything.
Is there something disturbing that lattepanda initializing or booting?