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