UART Anomaly

Hello everyone,

I have a system that includes a motherboard which is designed by me and a Jetson Nano. I’m trying to make communication between these cards with using UART. Jetson Nano’s baudrate is 115200. When I try to send 10 bytes from Jetson Nano to my motherboard, I’m getting a 50MHz sinusoidal wave. Actually I set a pin to digital and making it high and low and I got 50MHz sinusoidal wave. When I measure that pin’s voltage, I got 1.7V instead of 3.3V.

Is it normal or am I doing something wrong?

Please check this app note first to make sure the load of the pins are as requested.

And also this configuration doc: