2019-06-05 12:37 PM
The HX711 requires the MCU to send an exact number of clock pulses to capture a 24 bit value, then the clock signal must remain low until the HX711 indicates its ready to transmit again, using the data line. I tried to use a GPIO pin to generate the clock signal manually with pin_set and pin_reset calls, which works in that it creates a clock signal at the frequency of the APB, but the amplitude is only 100 mv. When I plug the clock signal into the HX711 the signal becomes low level noise. Here is the pin config:
  /*Configure GPIO pin : SCLK_Pin */
  GPIO_InitStruct.Pin = SCLK_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(SCLK_GPIO_Port, &GPIO_InitStruct);and here is the clock gen code:
	// read 24 data bits
	for (i = 0; i < 24; i++) {
	    HAL_GPIO_WritePin (SCLK_GPIO_Port, SCLK_Pin, GPIO_PIN_SET);
	    buffer <<= 1;
	    HAL_GPIO_WritePin (SCLK_GPIO_Port, SCLK_Pin, GPIO_PIN_RESET);
	    buffer += HAL_GPIO_ReadPin (SDATA_GPIO_Port, SDATA_Pin);
	}I should be getting a 3.3V clock signal. Any suggestions?
2019-06-05 12:48 PM
Read the datasheet carefully again. You need at least 25 bit cycles. And when, for example, some interrupt prolongs your SCK high for longer than 50 us, you get a reset. So you better read with interrupts disabled. With 26 or 27 bit you select the other channel ot another gain.
2019-06-05 1:52 PM
Uwe, thats good information but doesn't address the problem: a weak clock signal. My code snippet is not the whole app, just the parts that deal with this issue.
2019-06-06 1:52 AM
What SCK frequency do you get with above code? How is the HX711 connected? Maybe GPIO_SPEED_FREQ_LOW will result in the setup above in a "weak clock signal"?
2019-06-06 2:03 AM
Do you have the clock to the "SCLK_Port" enabled ?
SCLK_Port is just a define for a "real" port like A, B, ...
Anything other connected to that pin ?
This is a common issue with ST's Discovery board.
> ... , then the clock signal must remain low until the HX711 indicates its ready to transmit again ...
This suggests you want a pull-down resistor, rather then the pull-up you configured.
An external pull-down would be better, as it works even with unconfigured GPIOs, avoiding troublesome transitional signals during startup.
2019-06-06 11:45 AM
I tried another pin and am now getting a nice 3.3v signal. For reference, I am using the Nucleo F413 (aka Nucleo 144). The pin that gave me trouble was PE2. Pin PA6 works. As I mentioned in my initial question, the clock speed is the speed of the APB that the port is driven by. Thanks for your suggestions.
2019-11-27 3:13 AM
Hey!
I am a newby, but i am i a school project where i have to do a scale.
I set up the hx711 and the load cell with my nucleo card, but the card does not se
d clock signal to the hx711.
I am using a hx711 library i found at:
github.com/freakone/HX711
Could you please help me?!:folded_hands:
Thanks in advance.
2019-11-28 10:07 AM
2019-11-28 10:17 AM
Of course,
I use CubeMX to configurate the pins as u can see in the first picture.
And here is my code:
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>© Copyright (c) 2019 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */
 
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "dma.h"
#include "usart.h"
#include "gpio.h"
 
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "hx711.h"
#include "string.h"
/* USER CODE END Includes */
 
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
 
/* USER CODE END PTD */
 
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
 
/* USER CODE END PD */
 
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
 
/* USER CODE END PM */
 
/* Private variables ---------------------------------------------------------*/
 
/* USER CODE BEGIN PV */
volatile int meres =0;
volatile int meresAtlag =0;
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
 
/* USER CODE END PFP */
 
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
 
/* USER CODE END 0 */
 
/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* USER CODE BEGIN 1 */
  HX711 hx11;
  hx11.gpioSck = HS711SCK_GPIO_Port;
  hx11.gpioData = HX711OUTPUT_GPIO_Port;
  hx11.pinSck = HS711SCK_Pin;
  hx11.pinData = HX711OUTPUT_Pin;
  hx11.offset = 0;
  hx11.gain = 64;
 
  /* 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();
  MX_USART2_UART_Init();
  MX_DMA_Init();
  /* USER CODE BEGIN 2 */
  HX711_Init(hx11);
 
uint8_t masage[100];
//uint8_t times = 4;
 
//uint8_t times = 4;
//meresAtlag = HX711_AverageValue(hx11,  times);
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
	  meres = HX711_Value(hx11);
	  //meres = HX711_AverageValue(hx11, times);
	  HAL_Delay(500);
	  HAL_UART_Transmit(&huart2, masage, sprintf(masage,"%d\n\r", meres),1000);
    /* 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 = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI_DIV2;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL16;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** 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_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}
 
/* USER CODE BEGIN 4 */
 
/* USER CODE END 4 */
 
/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
 
  /* 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****/#include "hx711.h"
 
void HX711_Init(HX711 data)
{
//	GPIO_InitTypeDef GPIO_InitStruct;
//	GPIO_InitStruct.Pin = data.pinSck;
//	GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
//	GPIO_InitStruct.Pull = GPIO_NOPULL;
//	GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
//	HAL_GPIO_Init(data.gpioSck, &GPIO_InitStruct);
//
//	GPIO_InitStruct.Pin = data.pinData;
//	GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
//	GPIO_InitStruct.Pull = GPIO_PULLUP;
//	GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
//	HAL_GPIO_Init(data.gpioData, &GPIO_InitStruct);
 
	HAL_GPIO_WritePin(data.gpioSck, data.pinSck, GPIO_PIN_SET);
	HAL_Delay(50);
	HAL_GPIO_WritePin(data.gpioData, data.pinSck, GPIO_PIN_RESET);
 
}
 
int HX711_Average_Value(HX711 data, uint8_t times)
{
    int sum = 0;
    for (int i = 0; i < times; i++)
    {
        sum += HX711_Value(data);
    }
 
    return sum / times;
}
 
int HX711_Value(HX711 data)
{
    int buffer;
    buffer = 0;
 
    while (HAL_GPIO_ReadPin(data.gpioData, data.pinData)==1)
    ;
 
    for (uint8_t i = 0; i < 24; i++)
    {
    	HAL_GPIO_WritePin(data.gpioSck, data.pinSck, GPIO_PIN_SET);
 
        buffer = buffer << 1 ;
 
        if (HAL_GPIO_ReadPin(data.gpioData, data.pinData))
        {
            buffer ++;
        }
 
        HAL_GPIO_WritePin(data.gpioSck, data.pinSck, GPIO_PIN_RESET);
    }
 
    for (int i = 0; i < data.gain; i++)
    {
    	HAL_GPIO_WritePin(data.gpioSck, data.pinSck, GPIO_PIN_SET);
    	HAL_GPIO_WritePin(data.gpioSck, data.pinSck, GPIO_PIN_RESET);
    }
 
    buffer = buffer ^ 0x800000;
 
    return buffer;
}
 
HX711 HX711_Tare(HX711 data, uint8_t times)
{
    int sum = HX711_Average_Value(data, times);
    data.offset = sum;
    return data;
}
 #ifndef HX711_H_
#define HX711_H_
 
//#include "stm32f3xx_hal.h"
#include "main.h"
 
typedef struct _hx711
{
	GPIO_TypeDef* gpioSck;
	GPIO_TypeDef* gpioData;
	uint16_t pinSck;
	uint16_t pinData;
	int offset;
	int gain;
	// 1: channel A, gain factor 128
	// 2: channel B, gain factor 32
    // 3: channel A, gain factor 64
} HX711;
 
 
void HX711_Init(HX711 data);
HX711 HX711_Tare(HX711 data, uint8_t times);
int HX711_Value(HX711 data);
int HX711_AverageValue(HX711 data, uint8_t times);
 
#endif /* HX711_H_ */And it retuns 8388608 in the meres variable.
:(
Thanks for helping me!
2019-12-02 1:45 AM
Could you share your code so maybe I can figure out something?
Thanks in advance!
