STM32H745I-DISCO UART communication problem

[EnesUNLU]

Hello everyone,

First of all I am kinda new in ARM (I never use), I am working on the STM32H745I-DISCO board (using the CM7 core) and I am facing a persistent issue with UART . No matter what I try, the RX Interrupt never triggers, and the code never enters the HAL_UART_RxCpltCallback.

My Setup: Board: STM32H745I-DISCO

IDE: STM32CubeIDE (Latest Version)

Scenario: UART Loopback Test (Connecting TX to RX physically).

Peripheral: USART6 (TX: PC6 / RX: PC7) on the Arduino Headers (D1/D0).

Settings: 115200 baud, 8N1, Asynchronous.

The Problem:

-HAL_UART_Transmit works fine (signals observed). HAL_UART_Receive_IT returns HAL_OK. However, the HAL_UART_RxCpltCallback is never executed.  When checking SFRs in Debug mode: RXNE flag stays at 0.

What I have verified so far (Step-by-Step):

NVIC Settings: USART6 global interrupt is Enabled in CubeMX.

Vector Table: USART6_IRQHandler exists in stm32h7xx_it.c and calls HAL_UART_IRQHandler.

Initialization Order: I ensured that MX_USART6_UART_Init() is called BEFORE HAL_UART_Receive_IT in main.c.

Cache Management: I know H7 has cache coherence issues, so I completely Disabled D-Cache (SCB_DisableDCache()) at the beginning of main() to avoid DMA/Buffer issues (even though I am using IT, not DMA).

Hardware: Tested with a jumper wire between PC6 and PC7. I also tried different UART pins (like UART3 VCP), but the result is the same.(Also I tried another pins and UARTx or USARTy )

HardFault: Previously I had HardFaults due to init order, but that is fixed. The code runs, the while(1) loop blinks the LED, but no interrupt occurs.
Can someone help me?

[EnesUNLU]

-UPDATE-
As you guys mentioned I check pins with multimeter and I saw there is no Voltage in any pin (PB10 and PB11). Why it is occur does anyone know:/ I will Start new STM32 Project and try it again.

[mƎALLEm]

Hello,

Please share your project so we can look at it closely.

[EnesUNLU]

I attached my project as .rar

[mƎALLEm · Accepted solution]

Hello,

It seems the VCP connection has been changed from the board rev B01 to B02 from USART3 to USART1:

Rev B01:

Rev B02. and starting from Rev 2, USART1 is used with VCP instead of USART3:

So check the revision of your board:

If B02 or later you need to use USART1. I've attached a project where USART1 is used and Tx and Rx are looped back and the Rx callback is continuously called each character is received.

Hope that helps.

[EnesUNLU]

Thanks for that information I will try it now but I checked that you said and I have "B03". I was using revision "B01" as you mentioned. How can I find "B03" or I can still use "B02" ?

[mƎALLEm]

As I said starting from B02 you need to use USART1.

The different schematics' versions are available at this link:

Each schematics corresponds to a revision of the board.

So now please retry with the project I shared and get back to me with the result.

[mƎALLEm]

@EnesUNLU 

That's not the correct post to accept as solution:

You need accept the previous one (below) as it answers your original question:

[EnesUNLU]

Dear @mƎALLEm and all community, 
Thank you all for your helpfulness and consideration. Finally I solved the problem I changed the code entirely and I write from your code taking sample by sample. As you mentioned probably It was because of "different schematic problem" . After the changing pins In debug I saw variable rx is increasing and I can measure output voltage 3.3V (From D1/Tx pin).
Probably I will have another questions in soon :D