trying to interface with an HX711 load cell amp

[GrantW]

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?

[GrantW]

The following code works. Make sure that the buffer (and returned value) are defined uint32_t. The line "buffer ^= 0x800000;" is essential to avoid the huge #'s starting with 8.

uint32_t CB_SPI_Receive (void) {

uint32_t buffer = 0U;

int i, j, k = 1;

// wait for SDATA to go lo

while (HAL_GPIO_ReadPin (SDATA_GPIO_Port, SDATA_Pin)) ;

// wait 300 ns

for (j = 0; j < 5; j++) k += 19;

// 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);

}

// generate one or 3 more clock pulse to set gain for next sample and set bit 23 before returning

buffer ^= 0x800000;

// for (i = 0; i < 2; i++) {

HAL_GPIO_WritePin (SCLK_GPIO_Port, SCLK_Pin, GPIO_PIN_SET);

HAL_GPIO_WritePin (SCLK_GPIO_Port, SCLK_Pin, GPIO_PIN_RESET);

// }

return buffer;

}

[Uwe Bonnes]

Remember that SCK high longer than 50 us resets the chip. So block interrupts before you set SCK high and unblock after you have reset SCK.

[CüneytKüçük]

HI BROS,

I finally did it.Thank you for your help.

It works properly.

CODE:

#include "main.h"

#include "stm32f4xx_hal.h"

void SystemClock_Config(void);

static void MX_GPIO_Init(void);

uint8_t value=0;

uint8_t i = 0;

int32_t adc_value = 0;

#define pause for(int n=0;n<100;n++){};

int main(void)

{

 HAL_Init();

 SystemClock_Config();

 MX_GPIO_Init();

 while (1)

 {

 while (HAL_GPIO_ReadPin(GPIOD, GPIO_PIN_15));

 for(i=0;i<25;i++)

 {

 HAL_GPIO_WritePin(GPIOD, GPIO_PIN_13,GPIO_PIN_SET);

 //pause

 adc_value <<= 1;

 if(HAL_GPIO_ReadPin(GPIOD, GPIO_PIN_15))adc_value++;

 HAL_GPIO_WritePin(GPIOD, GPIO_PIN_13,GPIO_PIN_RESET);

 //pause

 };

for (int i = 0; i < 128; i++) {

HAL_GPIO_WritePin(GPIOD, GPIO_PIN_13,GPIO_PIN_SET);

HAL_GPIO_WritePin(GPIOD, GPIO_PIN_13,GPIO_PIN_RESET);

}

//adc_value = adc_value ^ 0x800000;

  while(adc_value>=255)adc_value>>=8;

  value=adc_value;

  adc_value=0;

 }

 }

void SystemClock_Config(void)

{

 RCC_OscInitTypeDef RCC_OscInitStruct = {0};

 RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

 /** 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 = RCC_HSICALIBRATION_DEFAULT;

 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;

 RCC_OscInitStruct.PLL.PLLM = 8;

 RCC_OscInitStruct.PLL.PLLN = 192;

 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;

 RCC_OscInitStruct.PLL.PLLQ = 7;

 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_DIV4;

 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)

 {

Error_Handler();

 }

}

static void MX_GPIO_Init(void)

{

 GPIO_InitTypeDef GPIO_InitStruct = {0};

 /* GPIO Ports Clock Enable */

 __HAL_RCC_GPIOB_CLK_ENABLE();

 __HAL_RCC_GPIOD_CLK_ENABLE();

 /*Configure GPIO pin Output Level */

 HAL_GPIO_WritePin(GPIOD, LD4_Pin|LD3_Pin|LD5_Pin, GPIO_PIN_RESET);

 /*Configure GPIO pins : LD4_Pin LD3_Pin LD5_Pin */

 GPIO_InitStruct.Pin = GPIO_PIN_13;

 GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;

 GPIO_InitStruct.Pull = GPIO_PULLUP ;

 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;

 HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

 /*Configure GPIO pin : PD15 */

 GPIO_InitStruct.Pin = GPIO_PIN_15;

 GPIO_InitStruct.Mode = GPIO_MODE_INPUT;

 GPIO_InitStruct.Pull = GPIO_PULLUP ;

 HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

}

void Error_Handler(void)

{

}

#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****/

[Attila_S]

Congrats mate, thnaks for sharing ☺�?​

[Vsing.22]

hey were you able to solve the 8404695 value issue ?

[CüneytKüçük]

Hi Bro's,

The weight values ​​are read properly, but how can I calibrate? Do you have any idea about this?

[GrantW]

That you will have to solve on your own. Hint: its simple math and known weights.

[GSant.3]

Hi everybody... I have the STM32F103C8T6 "bluepill".. i want to conect whit the HX711 using arduino IDE, but doesnt work, someone did this project?