STM32模拟SPI时序配置读取双路24位模数转换（24bit ADC）芯片ADS1220采样数据

TI公司的双路24位模数转换芯片ADS1220具有比较丰富的模式配置，双路差分输入采样也可以配置为4路单端输入信号采样。有多种参考电压源可选，内部增益（从1倍到128倍）和输出率（可达到2K/s）可配置，模拟电压和数字电路电压可单独设置等等。这里介绍STM32访问和读取ADS1220采样数据的代码实现，采用模拟SPI时序的方式。

市面上有测试用模块：

注意ADS1220内部只有一个ADC采样电路，所以虽然外部可以接两路差分输入源，实际上并不能同时采样，要进行输入通道切换，一个时间只能采样一个输入通道：

STM32电路连接

ADS1220的转换完成指示输出，可以通过单独的管脚/DRDY或者复用管脚DOUT/nDRDY输出，从减少逻辑复杂度考虑，优先采用单独的/DRDY管脚连接，从而DOUT/nDRDY只作为ADS1220数据输出管脚。因此STM32与ADS1220的标准连接为五线，在资源穷巴巴的情况下，可以调整电路和程序，从而实现只需要三线与STM32的连接，这种场景片选/CS始终拉低有效，而采用DOUT/nDRDY作为转换完成指示输出。这里介绍五线连接的代码实现。

ADS1220可以采用外部时钟源或者内部时钟源，一般可采用内部时钟源，需要将CLK管脚和DGND短路，从而上电或复位时，CLK管脚一定时间没有等到外部发来时钟，则会将内部电路切换到内部时钟源供应时钟。

ADS的AVDD和DVDD没有特别的相对大小设置，因此在连接STM32时，可以将AVDD连接到5V，而将DVDD连接到3.3V，从而SPI接口可以直接连接到STM32。需要注意，上电或复位时，芯片内部寄存器所有值置0，对应的参考电压为内部2.048V电压，而不是AVDD电压，可以通过芯片内部寄存器的配置，切换参考电压为AVDD，或者REFP0/REFN0, 其中一对差分信号输入采样通道也可以配置作为参考电压输入通道REFP1/REFN1，从而在应用中，最多可以切换4种参考电压，实现将24位采样能力规格化到不同电压范围内。只采用内部基准2.048V参考电压时，外部REFPx/REFNx可以不接。

上电时，默认为正常模式，单次转换模式，采用通道为AIN0/AIN1, 增益为1，采用内部基准电压2.048V， 输出速率一秒20次。

ADS1220测试电路

ADS1220典型的应用连接到惠斯通电桥，接收差分电压。简单测试可以采用如下方式：

当可调电阻器为10欧姆时，IN+和IN-差分电压为(5/(4700+4700+10))*10 = 5.31mV。可以微调可调电位器的阻值，调整输出差模电压。

ADS1220访问协议

ADS1220 SPI访问在时钟的上升沿输出数据，在时钟的下降沿采样数据。配置为单次转换模式时，发命令启动一次采样，可以读取到一次更新的采样数据。如果配置为连续转换模式，则可以发命令启动一次采样，后续自动进行连续采样，读取的时候不再发送采样启动命令。

手册相关关键描述部分：

注意配置寄存器0的MUX[3:0]进行采样输入通道选择，上电默认为AIN0-AIN1的输入通道：

STM32工程配置

这里采用STM32F103C6T6和STM32CUBEIDE开发环境，实现ADS1220的ADC数据读取代码。

首先配置基本工程和时钟系统：

STM32F103支持USB，可以实现虚拟串口，所以进行USB的配置，采用默认设置接口，另外配置UART2作为可选通讯口。

然后配置UART2：

选择5个通讯管脚，这里的选用：

PB0: /DRDY from ADS1220

PB1: /CS to ADS1220

PB4: DOUT from ADS1220

PB5: DIN to ADS1220

PB6: SCLK to ADS1220

保存并生成初始代码：

STM32工程代码

代码微秒级的时序控制，采用的微秒延时函数参考： STM32 HAL us delay（微秒延时）的指令延时实现方式及优化

STM32虚拟串口的设置可以参考： STM32 USB VCOM和HID的区别，配置及Echo功能实现（HAL）

编译时需要采用节省存储的编译方式，参考： STM32 region `FLASH‘ overflowed by xxx bytes 问题解决

代码在USB的控制文件里，将USB接收到的字节赋值给全局变量cmd，用来控制逻辑执行：

在收到0x01时，复位ADS1220在收到0x02时，关电ADS1220在收到0x03时，执行转换启动命令和单次采样数据读取（AIN0-AIN1的输入通道）在收到0x04时，直接读取当前采样数据（AIN0-AIN1的输入通道）在收到0x05时，设置ADS1220内部4个寄存器值，这里设置为连续转换模式在收到0x06时，读取ADS1220内部4个寄存器值在收到0x07时，执行转换启动命令和读取连续转换模式多个采样数据并获得平均值, 这里读取100次（AIN0-AIN1的输入通道）

main.c文件内容：

/* USER CODE BEGIN Header *//********************************************************************************* @file : main.c* @brief: Main program body******************************************************************************* @attention** Copyright (c) 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 /* 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 */#define cmd_reset 0x06#define cmd_start_sync 0x08#define cmd_powerdown 0x02#define cmd_rdata 0x10#define cmd_rreg 0x23 //read 4 bytes from all registers#define cmd_wreg 0x43 //write 4 bytes from all registers/* USER CODE END PD *//* Private macro -------------------------------------------------------------*//* USER CODE BEGIN PM */#define ads1220_rdy (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_0)==0)?1:0#define write_to_ads1220_cs_l HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_RESET)#define write_to_ads1220_cs_h HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_SET)#define write_to_ads1220_clk_l HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_RESET)#define write_to_ads1220_clk_h HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_SET)#define write_to_ads1220_din_l HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, GPIO_PIN_RESET)#define write_to_ads1220_din_h HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5, GPIO_PIN_SET)#define read_from_ads1220_dout HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_4)/* 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 ads1220_data;uint8_t Config_Reg_Read_Value[4];uint8_t Config_Reg_Write_Value[4];#define continuous_read_times 100uint32_t ads1220_data_all[continuous_read_times];uint64_t ads1220_data_avg = 0;/* 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();__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) //reset{write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_reset<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}PY_Delay_us_t(1);write_to_ads1220_cs_h ;while( CDC_Transmit_FS(&cmd, 1) != USBD_OK ) PY_Delay_us_t(1);cmd=0x00;}if(cmd==0x02) //Power down{write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_powerdown<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}PY_Delay_us_t(1);write_to_ads1220_cs_h ;while( CDC_Transmit_FS(&cmd, 1) != USBD_OK ) PY_Delay_us_t(1);cmd=0x00;}else if(cmd==0x03) //single read for single or continuous conversion{cmd=0x00;write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_start_sync<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}while(!ads1220_rdy);PY_Delay_us_t(1);ads1220_data = 0;for(uint8_t i=0;i<24;i++){write_to_ads1220_clk_h;PY_Delay_us_t(1);write_to_ads1220_clk_l;ads1220_data |= (read_from_ads1220_dout<<(23-i));PY_Delay_us_t(1);}PY_Delay_us_t(1);write_to_ads1220_cs_h ;while( CDC_Transmit_FS(&ads1220_data, 3) != USBD_OK ) PY_Delay_us_t(1);}else if(cmd==0x04) //Direct read despite of conversion status{cmd=0x00;write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_rdata<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}PY_Delay_us_t(1);ads1220_data = 0;for(uint8_t i=0;i<24;i++){write_to_ads1220_clk_h;PY_Delay_us_t(1);write_to_ads1220_clk_l;ads1220_data |= (read_from_ads1220_dout<<(23-i));PY_Delay_us_t(1);}PY_Delay_us_t(1);write_to_ads1220_cs_h ;while( CDC_Transmit_FS(&ads1220_data, 3) != USBD_OK ) PY_Delay_us_t(1);}if(cmd==0x05) //Set all config registers{//Set config register value here ↓Config_Reg_Write_Value[0] = 0; //channel --> AINP = AIN0，AINN = AIN1Config_Reg_Write_Value[1] = 0x04; //Set continuous conversion modeConfig_Reg_Write_Value[2] = 0;Config_Reg_Write_Value[3] = 0;write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_wreg<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}PY_Delay_us_t(1);for(uint8_t k=0; k<4; k++){for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((Config_Reg_Write_Value[k]<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}PY_Delay_us_t(1);}PY_Delay_us_t(1);write_to_ads1220_cs_h ;while( CDC_Transmit_FS(&cmd, 1) != USBD_OK ) PY_Delay_us_t(1);cmd=0x00;}else if(cmd==0x06) //Read all config registers{cmd=0x00;write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_rreg<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}PY_Delay_us_t(1);for(uint8_t k=0; k<4; k++){Config_Reg_Read_Value[k]=0;for(uint8_t i=0;i<8;i++){write_to_ads1220_clk_h;PY_Delay_us_t(1);write_to_ads1220_clk_l;Config_Reg_Read_Value[k] |= (read_from_ads1220_dout<<(7-i));PY_Delay_us_t(1);}PY_Delay_us_t(1);}write_to_ads1220_cs_h ;while( CDC_Transmit_FS(Config_Reg_Read_Value, 4) != USBD_OK ) PY_Delay_us_t(1);}else if(cmd==0x07) //Continuous read{cmd=0x00;write_to_ads1220_clk_l;write_to_ads1220_cs_l ;PY_Delay_us_t(1);for(uint8_t i=0; i<8; i++){write_to_ads1220_clk_h;if((cmd_start_sync<<i)&0x80) write_to_ads1220_din_h;else write_to_ads1220_din_l;PY_Delay_us_t(1);write_to_ads1220_clk_l;PY_Delay_us_t(1);}for(uint32_t j=0; j<continuous_read_times; j++){while(!ads1220_rdy);PY_Delay_us_t(1);ads1220_data_all[j] = 0;for(uint8_t i=0;i<24;i++){write_to_ads1220_clk_h;PY_Delay_us_t(1);write_to_ads1220_clk_l;ads1220_data_all[j] |= (read_from_ads1220_dout<<(23-i));PY_Delay_us_t(1);}PY_Delay_us_t(1);}write_to_ads1220_cs_h ;while( CDC_Transmit_FS(ads1220_data_all, 4*continuous_read_times) != USBD_OK ) PY_Delay_us_t(1);ads1220_data_avg = 0;for(uint32_t k=0; k<continuous_read_times; k++){ads1220_data_avg += ads1220_data_all[k];}ads1220_data_avg /= continuous_read_times;PY_Delay_us_t(100000);while( CDC_Transmit_FS(&ads1220_data_avg, 3) != USBD_OK ) PY_Delay_us_t(1);}else;PY_Delay_us_t(200000);/* 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_1, GPIO_PIN_SET);/*Configure GPIO pin Output Level */HAL_GPIO_WritePin(GPIOB, GPIO_PIN_5|GPIO_PIN_6, GPIO_PIN_RESET);/*Configure GPIO pins : PB0 PB4 */GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_4;GPIO_InitStruct.Mode = GPIO_MODE_INPUT;GPIO_InitStruct.Pull = GPIO_NOPULL;HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);/*Configure GPIO pins : PB1 PB5 PB6 */GPIO_InitStruct.Pin = GPIO_PIN_1|GPIO_PIN_5|GPIO_PIN_6;GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;GPIO_InitStruct.Pull = GPIO_NOPULL;GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;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代码测试

通过串口工具发送0x01复位ADS1220：

通过串口工具发送0x02关电ADS1220：

通过串口工具发送0x03读取采样值：

通过串口工具发送0x04读取采样值：

通过串口工具发送0x05设置寄存器内容：

通过串口工具发送0x06读取寄存器内容：

通过串口工具发送0x07读取100次采样值和平均值：

代码实现十六进制数据输出，如果要切换为串口printf打印输出，可以参考：

STM32 UART串口printf函数应用及浮点打印代码空间节省 (HAL)

例程下载

STM32F103C6T6模拟SPI协议读取双通道24位模数转换（24bit ADC）芯片ADS1220数据例程

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