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I can't for the life of me figure out why I can't get an external LED to blink.

I'm using Keil uVision 5 and STM32CubeMX; I've configured PD0 to be in output push/pull, with no pull up and no pull down, output speed low using Cube, and I've also set up the LED drivers from board support.

I can get the onboard LEDs connected to PJ5 and PJ13 to blink fine, however I cannot get the external LED, which seems to be configured exactly identically to the LED drivers, to blink. I have a 470 ohm resistor connected to PD0, and then the LED connected to that, and then the LED goes to ground.

I'm using HAL_GPIO_TogglePin to try to flip flop the state every second.

I've tried going into the board debugger to see what's up. In the debugger, I can manually toggle the onboard LEDs by checking their pin's boxes in the ODR register, and indeed PD0's ODR bit is flip flopping correctly, but the external LED is just not flipping.

I've confirmed that the LED is working by removing the jumper into PD0 and instead connecting it to 3.3v, and it works fine. I've tried using other output pins on the board from Port A and D, but to no avail.

I feel like I must be missing something really obvious but I can't figure out what. Let me know if there is any more info I can provide.

Here's my main.c:

/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  ** This notice applies to any and all portions of this file
  * that are not between comment pairs USER CODE BEGIN and
  * USER CODE END. Other portions of this file, whether 
  * inserted by the user or by software development tools
  * are owned by their respective copyright owners.
  *
  * COPYRIGHT(c) 2018 STMicroelectronics
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "stm32f7xx_hal.h"

/* USER CODE BEGIN Includes */
#include "Board_LED.h"                  // ::Board Support:LED
#include "Board_Buttons.h"              // ::Board Support:Buttons

/* USER CODE END Includes */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);

/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/

/* USER CODE END PFP */

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  *
  * @retval None
  */
int main(void)
{
  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration----------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  /* USER CODE BEGIN 2 */
    LED_Initialize();
    Buttons_Initialize();
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
        HAL_Delay(1000);
            LED_On(0);
            LED_On(1);
            HAL_GPIO_TogglePin(GPIOD,GPIO_PIN_0);

        HAL_Delay(1000);
            LED_Off(0);
            LED_Off(1);
            HAL_GPIO_TogglePin(GPIOD,GPIO_PIN_0);


  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */

  }
  /* USER CODE END 3 */

}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

    /**Configure the main internal regulator output voltage 
    */
  __HAL_RCC_PWR_CLK_ENABLE();

  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    /**Initializes the CPU, AHB and APB busses clocks 
    */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = 16;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLM = 8;
  RCC_OscInitStruct.PLL.PLLN = 216;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Activate the Over-Drive mode 
    */
  if (HAL_PWREx_EnableOverDrive() != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Initializes the CPU, AHB and APB busses clocks 
    */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_7) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure the Systick interrupt time 
    */
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

    /**Configure the Systick 
    */
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}

/** Configure pins as 
        * Analog 
        * Input 
        * Output
        * EVENT_OUT
        * EXTI
*/
static void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOD_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_0, GPIO_PIN_SET);

  /*Configure GPIO pin : PD0 */
  GPIO_InitStruct.Pin = GPIO_PIN_0;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @param  file: The file name as string.
  * @param  line: The line in file as a number.
  * @retval None
  */
void _Error_Handler(char *file, int line)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  while(1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t* file, uint32_t line)
{ 
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

/**
  * @}
  */

/**
  * @}
  */

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
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  • \$\begingroup\$ PD0 is (one of many pins) used by the FMC to talk to the external SDRAM. Are you sure you can use it as an IO? \$\endgroup\$ – brhans Oct 5 '18 at 2:15
  • \$\begingroup\$ Hmm, no, I am not sure, I assumed it was fine because it is one of only 22 pins made available via the female headers on the bottom of the discovery board. When setting up Cube, I cleared all pins, so the only one conifgured for anything is PD0 (and then using the LED drivers from board support to configure PJ5/13). I don't get any errors or warnings for any of the peripherals (including FMC) in Cube. I would assume it's fine because Cube gives me GPIO_Output as one of the options for that pin, and I am certainly not using FMC right now... \$\endgroup\$ – SamW Oct 5 '18 at 2:19
  • \$\begingroup\$ What’s that LED_On(0) function in your code? \$\endgroup\$ – Stefan Wyss Oct 5 '18 at 4:31
  • \$\begingroup\$ That is from LED_769I_Discovery.c, part of the Board Support/LED(API) driver included in the project via the Manage RunTimeEnviornment setup. It is what is successfully turning on and off the on-board LEDs at PJ5/13. It just uses HAL_GPIO_WritePin(port,pinnumber, GPIO_PIN_SET/RESET) to set the pins. I can show you that driver, but it shouldn't affect PD0/PA0 etc. I've compared and the initialization for the LEDs on PJ5/PJ13 within that file is as far as I can tell identical to what I've done for PD0. \$\endgroup\$ – SamW Oct 5 '18 at 4:46
  • \$\begingroup\$ What is PJ5 and PJ13? Don't know much about this HAL Abstraction but have you configured the pins as Output? \$\endgroup\$ – MaNyYaCk Oct 5 '18 at 7:22
0
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Problem solved - I was initializing pins indicated by the markings on the circuit board next to the female headers (eg D0-D15, B0, B1, etc), but it turns out these are not the name the of the pins those headers are connected to, but rather the names of the connections for an Arduino I guess. I was able to find the the name of the actually microcontroller pins which these were connected to in the data sheet/user manual.

I assumed they were the same, but turns out they absolutely aren’t! So another case of RTFM.

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