HX711 with a Four Wire Load Cell with Blue Pill using STM32CubeIDE

Prerequisites

This project assumes you have already installed STM32CubeIDE. You need to have previously done a basic blink sketch with blue-pill using STM32CubeIDE. I have made a complete video from installing STM32CubeIDE to LED blink program. You can watch it by clicking this link. https://www.youtube.com/watch?v=kXg467nVd_A

Wiring Diagram

STM32CubeIDE Settings

Click RCC → High Speed Clock (HSE) to Crystal/Ceramic Resonator

Click Clock Configuration tab → HCLK (MHz) to 72

Click Pinout and Configuration tab

Click Timer → Click TIM2 →

Clock Source set to Internal Clock

Configuration → Parameter Settings →

Prescaler set to 71

Set PB9 GPIO_Output

Set PB8 GPIO_Input

Additional code on top of STM32CubeIDE generated code

/* USER CODE BEGIN 0 */
#define DT_PIN GPIO_PIN_8
#define DT_PORT GPIOB
#define SCK_PIN GPIO_PIN_9
#define SCK_PORT GPIOB

uint32_t tare = 0; 
float knownOriginal = 1;  // in milli gram
float knownHX711 = 1; 
int weight;

void microDelay(uint16_t delay)
{
  __HAL_TIM_SET_COUNTER(&htim2, 0);
  while (__HAL_TIM_GET_COUNTER(&htim2) < delay);
}

int32_t getHX711(void)
{
  uint32_t data = 0;
  uint32_t startTime = HAL_GetTick();
  while(HAL_GPIO_ReadPin(DT_PORT, DT_PIN) == GPIO_PIN_SET)
  {
    if(HAL_GetTick() - startTime > 200)
      return 0;
  }
  for(int8_t len=0; len<24 ; len++)
  {
    HAL_GPIO_WritePin(SCK_PORT, SCK_PIN, GPIO_PIN_SET);
    microDelay(1);
    data = data << 1;
    HAL_GPIO_WritePin(SCK_PORT, SCK_PIN, GPIO_PIN_RESET);
    microDelay(1);
    if(HAL_GPIO_ReadPin(DT_PORT, DT_PIN) == GPIO_PIN_SET)
      data ++;
  }
  data = data ^ 0x800000;
  HAL_GPIO_WritePin(SCK_PORT, SCK_PIN, GPIO_PIN_SET);
  microDelay(1);
  HAL_GPIO_WritePin(SCK_PORT, SCK_PIN, GPIO_PIN_RESET);
  microDelay(1);
  return data;
}

int weigh()
{
  int32_t  total = 0;
  int32_t  samples = 50;
  int milligram;
  float coefficient;
  for(uint16_t i=0 ; i<samples ; i++)
  {
      total += getHX711();
  }
  int32_t average = (int32_t)(total / samples);
  coefficient = knownOriginal / knownHX711;
  milligram = (int)(average-tare)*coefficient;
  return milligram;
}
/* USER CODE END 0 */

  /* USER CODE BEGIN 2 */
  HAL_TIM_Base_Start(&htim2);
  HAL_GPIO_WritePin(SCK_PORT, SCK_PIN, GPIO_PIN_SET);
  HAL_Delay(10);
  HAL_GPIO_WritePin(SCK_PORT, SCK_PIN, GPIO_PIN_RESET);
  HAL_Delay(10);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    weight = weigh(); // in milligram
    /* USER CODE END WHILE */

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