STM32H723 Nucleo: UART4 not working

[BrotherTheo]

I am stumped and frustrated. I wrote some test code to test UART4. It worked fine. Then I moved the test code over to my main project and now I get no UART interrupts. Both code sets run on the same hardware. I have checked to make sure the UART RX was on the right pin, checked the NVIC settings, even went into the UART registers looking for a difference. Any ideas? 

main code:

HAL_UART_Receive_IT(&huart4, rx_buff, 1);

IRQ handler:

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	static uint8_t		MeasState=0;	//0=meas, 1=calc
	static uint32_t		OldSample;
	uint32_t			NewSample;
	//static uint32_t		OldTimerValue;
	uint32_t			NewTimerValue;

	if(rx_buff[0]==0xF8)
	{
		if(MeasState==0)
		{
			OldSample=__HAL_TIM_GET_COUNTER(&htim23);
			MeasState=1;
		} else
		{
			NewSample=__HAL_TIM_GET_COUNTER(&htim23);
			MeasState=0;
			NewTimerValue = (NewSample-OldSample)/2560;
			//TIM2->ARR = NewTimerValue;
			__HAL_TIM_SET_AUTORELOAD(&htim2,NewTimerValue);
		}
	}
	HAL_UART_Receive_IT(&huart4, rx_buff, 1);
}

[Karl Yamashita]

Which pins are you using? PA0/PA1? If so, PA1 is connected to the ethernet controller.

Try PD0 and PD1, or the other possible pin combinations for UART4.

[BrotherTheo]

Using PD0/PD1. Also my test code runs on this hardware with the same pins.

[Karl Yamashita]

You must be on the wrong pins on the Nucleo? 

I've tested UART4 using PD0 and PD1 and I get interrupts.

Here is just a simple code that I used to test receiving 0xF8 and replying back with 01 02 03

/*
 * PollingRoutine.c
 *
 *  Created on: Oct 24, 2023
 *      Author: karl.yamashita
 *
 *
 *      Template for projects.
 *
 *      The object of this PollingRoutine.c/h files is to not have to write code in main.c which already has a lot of generated code.
 *      It is cumbersome having to scroll through all the generated code for your own code and having to find a USER CODE section so your code is not erased when CubeMX re-generates code.
 *      
 *      Direction: Call PollingInit before the main while loop. Call PollingRoutine from within the main while loop
 * 
 *      Example;
        // USER CODE BEGIN WHILE
        PollingInit();
        while (1)
        {
            PollingRoutine();
            // USER CODE END WHILE

            // USER CODE BEGIN 3
        }
        // USER CODE END 3

 */


#include "main.h"


extern UART_HandleTypeDef huart4;

uint8_t uart4rxData[1] = {0};
uint8_t txData[] = {0x11,0x22,0x33,0x44,0x55};

bool uart4Flag = false;

// called before main while loop
void PollingInit(void)
{
	HAL_UART_Receive_IT(&huart4, uart4rxData, 1);

	HAL_UART_Transmit_IT(&huart4, txData, 5);
}

// called from inside main while loop
void PollingRoutine(void)
{
	UART_CheckFlag();
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	if(huart == &huart4)
	{
		uart4Flag = 1;
		HAL_UART_Receive_IT(&huart4, uart4rxData, 1);
	}
}

void UART_CheckFlag(void)
{
	if(uart4Flag)
	{
		uart4Flag = 0;
		if(uart4rxData[0] == 0xF8)
		{
			txData[0] = 1;
			txData[1] = 2;
			txData[2] = 3;
			HAL_UART_Transmit_IT(&huart4, txData, 3);
		}
	}
}

This is the output from Docklight

2/12/2025 18:37:53.375 [RX] - 11 22 33 44 55 
2/12/2025 18:37:57.417 [TX] - F8 
2/12/2025 18:37:57.432 [RX] - 01 02 03 
2/12/2025 18:38:05.903 [TX] - F8 
2/12/2025 18:38:05.915 [RX] - 01 02 03 
2/12/2025 18:38:12.999 [TX] - F8 
2/12/2025 18:38:13.008 [RX] - 01 02 03 

Are you sure you have PD0 as Rx? It's reversed compared to PA0/PA1 where PA1 is Rx. 

[BrotherTheo]

Yes, PD0 is the RX line.