STM32讀取24位模數(shù)轉(zhuǎn)換(24bit ADC)芯片HX711數(shù)據(jù)
HX711是一款國(guó)產(chǎn)低成本24位ADC芯片,常用于與稱重傳感器配合實(shí)現(xiàn)體重計(jì)的應(yīng)用。這里介紹STM32讀取HX711的電路和代碼實(shí)現(xiàn)。
HX711的內(nèi)部原理如下圖所示:
市面上有普通和帶屏蔽的兩種模塊:
STM32電路連接
STM32可直接與HX711進(jìn)行連接,選擇2個(gè)具有FT(5V耐壓)的管腳,將其中對(duì)應(yīng)時(shí)鐘輸出的管腳配置為Open-drain輸出,通過1K歐姆電阻上拉到HX711的供電電壓,將對(duì)應(yīng)數(shù)據(jù)輸入的管腳配置為無上下拉的輸入模式,則HX711可配置為2.7~5.5V的供電范圍,不受限于STM32本身為3.3V供電的場(chǎng)景,實(shí)現(xiàn)正常通訊,注意上拉電阻不能太弱,此處不能用10K歐姆的上拉電阻。如下圖所示:
HX711測(cè)試電路
HX711典型的應(yīng)用連接到惠斯通電橋,接收差分電壓,由于A通道內(nèi)部已經(jīng)設(shè)計(jì)為128倍和64倍信號(hào)放大,所以對(duì)于5V供電(AVDD),最大檢測(cè)差分電壓范圍為±20mV及±40mV,而B通道內(nèi)部已設(shè)計(jì)為32倍信號(hào)放大,所以對(duì)于5V供電(AVDD),最大檢測(cè)差分電壓范圍為±80mV。
HX711內(nèi)部有反饋電路,通過反饋電路決定輸出AVDD電壓的值,此電壓既是內(nèi)部進(jìn)行ADC采樣的參考高電壓,也是可以輸出給外部電路的供電參考電壓。而AGND為參考低電壓與數(shù)字地共地,數(shù)據(jù)手冊(cè)介紹如下:
通過上面介紹的STM32通過選用FT特性管腳,及采用Open-drain連接方式,STM32和HX711的數(shù)字供電可以不同,注意這里只有時(shí)鐘管腳采用Open-drain連接方式,數(shù)據(jù)管腳仍然采用普通的無上下拉輸入模式,因?yàn)镠X711數(shù)據(jù)手冊(cè)里提到:
注意此芯片在輸入信號(hào)共模電壓方面有要求:
簡(jiǎn)單測(cè)試可以采用如下方式:
當(dāng)可調(diào)電阻器為10歐姆時(shí),IN+和IN-差分電壓為(5/(4700+4700+10))*10 = 5.31mV。而IN-端電壓為2.49734V,IN+端電壓為2.50265V,共模和差模電壓都在手冊(cè)電氣范圍內(nèi),可以微調(diào)可調(diào)電位器的阻值,調(diào)整輸出差模電壓。需要注意HX711的AVDD電壓,在轉(zhuǎn)換前輸出,在轉(zhuǎn)換后關(guān)閉,不是一直輸出。
HX711訪問協(xié)議
HX711通過控制時(shí)鐘管腳輸出低電平指示正常工作狀態(tài),然后識(shí)別數(shù)據(jù)輸入管腳的低電平狀態(tài)判斷當(dāng)前已完成轉(zhuǎn)換并可讀取數(shù)據(jù),然后發(fā)送出24個(gè)時(shí)鐘波形,并在每個(gè)時(shí)鐘波形的下降沿讀取數(shù)據(jù)位,先讀到的是24位采樣數(shù)據(jù)的高位。在24個(gè)時(shí)鐘后,還要發(fā)送1到3個(gè)時(shí)鐘波形,即第25~27的時(shí)鐘,指示后面的ADC轉(zhuǎn)換對(duì)應(yīng)的通道和增益, 如下所示:
具體的時(shí)序要求如下:
另外通過將時(shí)鐘輸出管腳輸出60us以上,可將HX711進(jìn)行復(fù)位。
轉(zhuǎn)換速度方面是通過硬件的RATE管腳高低電平進(jìn)行設(shè)置,拉低為10Hz,拉高為80Hz。另外可以控制芯片采用內(nèi)部還是外部時(shí)鐘,一般采用內(nèi)部時(shí)鐘將XI管腳拉低即可。
STM32工程配置
這里采用STM32F103C6T6和STM32CUBEIDE開發(fā)環(huán)境,實(shí)現(xiàn)HX711的ADC數(shù)據(jù)讀取。
首先配置基本工程和時(shí)鐘系統(tǒng):
STM32F103支持USB,可以實(shí)現(xiàn)虛擬串口,所以進(jìn)行USB的配置,采用默認(rèn)設(shè)置接口,另外配置UART2作為可選通訊口。
然后配置UART2:
選擇具有FT特征的PB0和PB1作為與HX711通訊的管腳,PB0作為時(shí)鐘管腳配置為Open-drain,PB1作為數(shù)據(jù)管腳配置為輸入。
保存并生成初始代碼:
STM32工程代碼
代碼主要實(shí)現(xiàn)微秒級(jí)的時(shí)序控制,采用的微秒延時(shí)函數(shù)參考: STM32 HAL us delay(微秒延時(shí))的指令延時(shí)實(shí)現(xiàn)方式及優(yōu)化
STM32虛擬串口的設(shè)置可以參考: STM32 USB VCOM和HID的區(qū)別,配置及Echo功能實(shí)現(xiàn)(HAL)
編譯時(shí)需要采用節(jié)省存儲(chǔ)的編譯方式,參考: STM32 region `FLASH‘ overflowed by xxx bytes 問題解決
代碼在USB的控制文件里,將USB接收到的字節(jié)賦值給全局變量cmd,用來控制邏輯執(zhí)行:
- 在收到0x01時(shí),A通道128倍增益測(cè)試
- 在收到0x02時(shí),B通道32倍增益測(cè)試
- 在收到0x03時(shí),A通道64倍增益測(cè)試
main.c文件完整代碼如下:
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2022 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
//Written by Pegasus Yu in 2022
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usb_device.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "string.h"
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
__IO float usDelayBase;
void PY_usDelayTest(void)
{
__IO uint32_t firstms, secondms;
__IO uint32_t counter = 0;
firstms = HAL_GetTick()+1;
secondms = firstms+1;
while(uwTick!=firstms) ;
while(uwTick!=secondms) counter++;
usDelayBase = ((float)counter)/1000;
}
void PY_Delay_us_t(uint32_t Delay)
{
__IO uint32_t delayReg;
__IO uint32_t usNum = (uint32_t)(Delay*usDelayBase);
delayReg = 0;
while(delayReg!=usNum) delayReg++;
}
void PY_usDelayOptimize(void)
{
__IO uint32_t firstms, secondms;
__IO float coe = 1.0;
firstms = HAL_GetTick();
PY_Delay_us_t(1000000) ;
secondms = HAL_GetTick();
coe = ((float)1000)/(secondms-firstms);
usDelayBase = coe*usDelayBase;
}
void PY_Delay_us(uint32_t Delay)
{
__IO uint32_t delayReg;
__IO uint32_t msNum = Delay/1000;
__IO uint32_t usNum = (uint32_t)((Delay%1000)*usDelayBase);
if(msNum>0) HAL_Delay(msNum);
delayReg = 0;
while(delayReg!=usNum) delayReg++;
}
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
#define hx711_rdy (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_1)==0)?1:0
#define hx711_clk_h HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_SET)
#define hx711_clk_l HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_RESET)
#define hx711_dout HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_1)
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
UART_HandleTypeDef huart2;
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART2_UART_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
uint8_t cmd=0;
uint32_t hx711_data;
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
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();
MX_USART2_UART_Init();
MX_USB_DEVICE_Init();
/* USER CODE BEGIN 2 */
PY_usDelayTest();
PY_usDelayOptimize();
hx711_clk_h;
PY_Delay_us_t(80); //soft reset hx711
hx711_clk_l;
PY_Delay_us_t(10);
__HAL_UART_CLEAR_FLAG(&huart2, UART_FLAG_RXNE);
HAL_UART_Receive_IT(&huart2, (uint8_t *)&cmd, 1);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
if(cmd==0x01) //Channel A, gain 128
{
while(hx711_rdy) ;
while(!hx711_rdy) PY_Delay_us_t(1);
hx711_data = 0;
PY_Delay_us_t(1);
for(uint8_t i=1;i<=24;i++)
{
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
hx711_data |= (hx711_dout<<(24-i));
PY_Delay_us_t(1);
}
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
PY_Delay_us_t(1);
while( CDC_Transmit_FS(&hx711_data, 3) != USBD_OK ) PY_Delay_us_t(1);
}
else if(cmd==0x02) //Channel B, gain 32
{
while(hx711_rdy) ;
while(!hx711_rdy) PY_Delay_us_t(1);
hx711_data = 0;
PY_Delay_us_t(1);
for(uint8_t i=1;i<=24;i++)
{
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
hx711_data |= (((uint32_t)hx711_dout)<<(24-i));
PY_Delay_us_t(1);
}
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
PY_Delay_us_t(1);
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
PY_Delay_us_t(1);
while( CDC_Transmit_FS(&hx711_data, 3) != USBD_OK ) PY_Delay_us_t(1);
}
else if(cmd==0x03) //Channel A, gain 64
{
while(hx711_rdy) ;
while(!hx711_rdy) PY_Delay_us_t(1);
hx711_data = 0;
PY_Delay_us_t(1);
for(uint8_t i=1;i<=24;i++)
{
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
hx711_data |= (hx711_dout<<(24-i));
PY_Delay_us_t(1);
}
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
PY_Delay_us_t(1);
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
PY_Delay_us_t(1);
hx711_clk_h;
PY_Delay_us_t(1);
hx711_clk_l;
PY_Delay_us_t(1);
while( CDC_Transmit_FS(&hx711_data, 3) != USBD_OK ) PY_Delay_us_t(1);
}
else;
PY_Delay_us_t(100000);
/* 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};
RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses 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();
}
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USB;
PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_PLL_DIV1_5;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief USART2 Initialization Function
* @param None
* @retval None
*/
static void MX_USART2_UART_Init(void)
{
/* USER CODE BEGIN USART2_Init 0 */
/* USER CODE END USART2_Init 0 */
/* USER CODE BEGIN USART2_Init 1 */
/* USER CODE END USART2_Init 1 */
huart2.Instance = USART2;
huart2.Init.BaudRate = 115200;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
huart2.Init.StopBits = UART_STOPBITS_1;
huart2.Init.Parity = UART_PARITY_NONE;
huart2.Init.Mode = UART_MODE_TX_RX;
huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart2.Init.OverSampling = UART_OVERSAMPLING_16;
if (HAL_UART_Init(&huart2) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USART2_Init 2 */
/* USER CODE END USART2_Init 2 */
}
/**
* @brief GPIO Initialization Function
* @param None
* @retval None
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOD_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_RESET);
/*Configure GPIO pin : PB0 */
GPIO_InitStruct.Pin = GPIO_PIN_0;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
/*Configure GPIO pin : PB1 */
GPIO_InitStruct.Pin = GPIO_PIN_1;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
}
/* USER CODE BEGIN 4 */
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle)
{
HAL_UART_Receive_IT(&huart2, (uint8_t *)&cmd, 1);
}
/* 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 */
__disable_irq();
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,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
STM32代碼測(cè)試
通過串口工具發(fā)送0x01,則進(jìn)行A通道128倍增益的測(cè)試(觀察工具左側(cè)接收的24位16進(jìn)制數(shù)據(jù)):
通過串口工具發(fā)送0x02,則進(jìn)行B通道32倍增益的測(cè)試(觀察工具左側(cè)接收的24位16進(jìn)制數(shù)據(jù)), 這里B通道輸入管腳都接地故無有效信號(hào)輸入:
通過串口工具發(fā)送0x03,則進(jìn)行A通道64倍增益的測(cè)試(觀察工具左側(cè)接收的24位16進(jìn)制數(shù)據(jù)):
可以看出0x01測(cè)試的數(shù)值差不多是0x03測(cè)試的2倍, 因?yàn)樵鲆嬲檬?28對(duì)64。
代碼實(shí)現(xiàn)十六進(jìn)制數(shù)據(jù)輸出,如果要切換為串口printf打印輸出,可以參考:
STM32 UART串口printf函數(shù)應(yīng)用及浮點(diǎn)打印代碼空間節(jié)省 (HAL)
例程下載
STM32F103C6T6-HX711例程文章來源:http://www.zghlxwxcb.cn/news/detail-401501.html
–End–文章來源地址http://www.zghlxwxcb.cn/news/detail-401501.html
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