STM32 MCO+SPI获取24位模数转换（24bit ADC）高速芯片ADS1271采样数据

STM32大部分芯片只有12位的ADC采样性能，如果要实现更高精度的模数转换如24位ADC采样，则需要连接外部ADC实现。ADS1271是 TI公司一款高速24位Σ-Δ型模数转换器(ADC) ,数据率达到105K SPS, 即一秒可以采样105000次。

这里介绍基于ADS1271的24位ADC采样实现。采用STM32CUBEIDE开发工具，以STM32F401CCU6为例。

ADS1271操作方式

ADS1271的管脚定义如下所示：

ADS1271采用双电压模式，即模拟电压和数字电压可以单独设置，因此典型应用为模拟电压接5V，数字电压接3.3V，从而数字逻辑管脚可以与STM32直接连接。
ADS1271有三种模式：高速，高分辨率和低功耗，这里只介绍高速模式的例程，其它的模式可以相应调整即可。因此MODE管脚拉低。
ADS1271有三种数据输出方式： SPI, MO, FS, 这里只介绍SPI模式，其它的模式可以相应调整即可。因此FORMAT管脚拉低。
/SYNC_/PDWN用作上下电控制，因此保持上电状态，一直拉高。
DIN管脚可以用作级联采样方式，这里只介绍单片采样方式，因此DIN管脚必须拉低。
DOUT为数据输出管脚，STM32输出上升沿给ADS1271时ADS1271送出数据，STM32输出下降沿时自身采样数据。
/DRDY_FSYNC用作ADS1271数据准备好的报告，对STM32为输入管脚连接。
SCLK为数据获取时钟，SCLK需要保证在两次/DRDY_FSYNC之间能够读取完一次ADS1271准备好的数据。
CLK为需要提供给ADS1271的高速时钟，最小值为100KHz，最大值为27MHz。这里通过STM32的MCO(Master Clock Out)专用功能管脚连接提供此时钟。
VREFP连接到一个2.5V左右的稳压源，因为管脚内部有４.２Ｋ阻值特性，因此可以在外部通过连接一个４.７Ｋ电阻到５Ｖ，为了提高参考电压稳定性，需要给５Ｖ电压放置一个大的滤波电容。
AINP/AINN则连接要采样的差分电压。
本例程的连接关系为：

STM32工程配置

首先创建基本工程并设置时钟：

配置MCO输出时钟频率为21MHz：

设置PA4为GPIO输入管脚作为/DRDY_FSYNC，设置SPI1作为数据获取接口：

只连接SPI1的PA5和PA6，作为时钟和数据获取管脚：

本例程不采用中断和DMA方式，直接配置接口参数：

配置USB虚拟串口作为数据输出端口：

保存并生成初始工程代码;

STM32工程代码

例程代码实现连续获取5000次采样数据后，做一次平均，再输出24位采样平均值。

完整的例程代码main.c：

/* USER CODE BEGIN Header */
/********************************************************************************* @file           : main.c* @brief          : Main program body******************************************************************************* @attention** Copyright (c) 2023 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.********************************************************************************/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usb_device.h"/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes *//* USER CODE END Includes *//* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD *//* USER CODE END PTD *//* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
__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 PD *//* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM *//* USER CODE END PM *//* Private variables ---------------------------------------------------------*/
SPI_HandleTypeDef hspi1;/* USER CODE BEGIN PV *//* USER CODE END PV *//* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_Init(void);
/* USER CODE BEGIN PFP *//* USER CODE END PFP *//* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */#define ADS1271_DRDY HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_4)uint32_t ads1271_data;
void ADS1271_Get_Data(void)
{while(ADS1271_DRDY!=0) PY_Delay_us_t(1);HAL_SPI_Receive(&hspi1, (uint8_t *)&ads1271_data, 3, 2700);while(ADS1271_DRDY==0) PY_Delay_us_t(1);
}#define avg_times 5000
/* USER CODE END 0 *//*** @brief  The application entry point.* @retval int*/
int main(void)
{/* USER CODE BEGIN 1 */uint32_t i;uint32_t Buff[avg_times];uint64_t sum = 0;uint32_t avg = 0;/* 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_USB_DEVICE_Init();MX_SPI1_Init();/* USER CODE BEGIN 2 */PY_usDelayTest();PY_usDelayOptimize();/* USER CODE END 2 *//* Infinite loop *//* USER CODE BEGIN WHILE */while (1){for(i=0; i<avg_times; i++){ADS1271_Get_Data();Buff[i] = ads1271_data;}sum = 0;for(i=0; i<avg_times; i++){sum += (Buff[i]>>16)|(Buff[i]&0x0000ff00)|((Buff[i]&0x000000ff)<<16);}avg = sum/avg_times;while(CDC_Transmit_FS((uint8_t*)&avg, 3)==USBD_BUSY) PY_Delay_us_t(1);/* 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};/** Configure the main internal regulator output voltage*/__HAL_RCC_PWR_CLK_ENABLE();__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE2);/** 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.PLL.PLLState = RCC_PLL_ON;RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;RCC_OscInitStruct.PLL.PLLM = 25;RCC_OscInitStruct.PLL.PLLN = 336;RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;RCC_OscInitStruct.PLL.PLLQ = 7;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_DIV4;RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK){Error_Handler();}HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_PLLCLK, RCC_MCODIV_4);
}/*** @brief SPI1 Initialization Function* @param None* @retval None*/
static void MX_SPI1_Init(void)
{/* USER CODE BEGIN SPI1_Init 0 *//* USER CODE END SPI1_Init 0 *//* USER CODE BEGIN SPI1_Init 1 *//* USER CODE END SPI1_Init 1 *//* SPI1 parameter configuration*/hspi1.Instance = SPI1;hspi1.Init.Mode = SPI_MODE_MASTER;hspi1.Init.Direction = SPI_DIRECTION_2LINES;hspi1.Init.DataSize = SPI_DATASIZE_8BIT;hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;hspi1.Init.NSS = SPI_NSS_SOFT;hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_8;hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;hspi1.Init.TIMode = SPI_TIMODE_DISABLE;hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;hspi1.Init.CRCPolynomial = 10;if (HAL_SPI_Init(&hspi1) != HAL_OK){Error_Handler();}/* USER CODE BEGIN SPI1_Init 2 *//* USER CODE END SPI1_Init 2 */}/*** @brief GPIO Initialization Function* @param None* @retval None*/
static void MX_GPIO_Init(void)
{GPIO_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 *//* GPIO Ports Clock Enable */__HAL_RCC_GPIOH_CLK_ENABLE();__HAL_RCC_GPIOA_CLK_ENABLE();/*Configure GPIO pin : PA4 */GPIO_InitStruct.Pin = GPIO_PIN_4;GPIO_InitStruct.Mode = GPIO_MODE_INPUT;GPIO_InitStruct.Pull = GPIO_PULLUP;HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);/*Configure GPIO pin : PA8 */GPIO_InitStruct.Pin = GPIO_PIN_8;GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;GPIO_InitStruct.Pull = GPIO_NOPULL;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;GPIO_InitStruct.Alternate = GPIO_AF0_MCO;HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}/* 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 */__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测试输出

串口测试输出如下：

STM32例程下载

STM32 MCO+SPI获取24位模数转换（24bit ADC）高速芯片ADS1271采样数据例程

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