UART TX and RX pin issue

[adithya_sharma]

Hello,

I am using "NUCLEO-H743Zi2" eval board. I am using it for UART communication. I had configured UART4 in it as following;

• PA0 as UART4_TX
• PA1 as UART4_RX

When I tried to transmit, it is not transmitting more than 2 bytes. While receiving, it is not at all consistent (random values are received).

So I checked board's schematic as following;

I saw that PA1 and PA0 are not directly connected to CN11 connector in the board. 

Is it causing UART4's transmission and reception error? 

Also if I want to operate UART4 using GPIO's PA0 and PA1 only, what is the solution?

[SofLit]

You need at least to remove SB57.

Seems your UART is disturbed by the clock coming from ETH PHY.

[adithya_sharma]

Thank you for replying.

I understood that for PA1 (rx pin) I might have to desolder SB57.

But what might be problem in PA0 (tx pin)?

[SofLit · Accepted solution]

Before going further, you can test with another alternate function not mapped on PA0 even it will not be your final design and check if the problem persist.

Ps: I think there is a capacitor connected to PA0 used for for button debouncing it could introduce some communication issues and does a signal filtering.