轮询接收数据原理
124.4.14轮询接收数据原理
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Inc/main.h
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.h
* @brief : Header for main.c file.
* This file contains the common defines of the application.
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __MAIN_H
#define __MAIN_H
#ifdef __cplusplus
extern "C" {
#endif
/* Includes ------------------------------------------------------------------*/
#include "stm32f1xx_hal.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */
/* USER CODE END ET */
/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */
/* USER CODE END EC */
/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */
/* USER CODE END EM */
/* Exported functions prototypes ---------------------------------------------*/
void Error_Handler(void);
/* USER CODE BEGIN EFP */
/* USER CODE END EFP */
/* Private defines -----------------------------------------------------------*/
#define LED2_Pin GPIO_PIN_5
#define LED2_GPIO_Port GPIOE
#define LED1_Pin GPIO_PIN_5
#define LED1_GPIO_Port GPIOB
/* USER CODE BEGIN Private defines */
/* USER CODE END Private defines */
#ifdef __cplusplus
}
#endif
#endif /* __MAIN_H */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Inc/gpio.h
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file gpio.h
* @brief This file contains all the function prototypes for
* the gpio.c file
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __GPIO_H__
#define __GPIO_H__
#ifdef __cplusplus
extern "C" {
#endif
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* USER CODE BEGIN Private defines */
/* USER CODE END Private defines */
void MX_GPIO_Init(void);
/* USER CODE BEGIN Prototypes */
/* USER CODE END Prototypes */
#ifdef __cplusplus
}
#endif
#endif /*__ GPIO_H__ */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Inc/usart.h
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file usart.h
* @brief This file contains all the function prototypes for
* the usart.c file
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __USART_H__
#define __USART_H__
#ifdef __cplusplus
extern "C" {
#endif
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/* USER CODE BEGIN Includes */
#include <stdio.h>
/* USER CODE END Includes */
extern UART_HandleTypeDef huart1;
/* USER CODE BEGIN Private defines */
extern uint8_t u_buf[256];
#define printf(...) HAL_UART_Transmit(&huart1, (uint8_t *)u_buf, sprintf((char*)u_buf, __VA_ARGS__), 0xffff)
/* USER CODE END Private defines */
void MX_USART1_UART_Init(void);
/* USER CODE BEGIN Prototypes */
/* USER CODE END Prototypes */
#ifdef __cplusplus
}
#endif
#endif /* __USART_H__ */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Inc/stm32f1xx_it.h
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file stm32f1xx_it.h
* @brief This file contains the headers of the interrupt handlers.
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 */
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __STM32F1xx_IT_H
#define __STM32F1xx_IT_H
#ifdef __cplusplus
extern "C" {
#endif
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */
/* USER CODE END ET */
/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */
/* USER CODE END EC */
/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */
/* USER CODE END EM */
/* Exported functions prototypes ---------------------------------------------*/
void NMI_Handler(void);
void HardFault_Handler(void);
void MemManage_Handler(void);
void BusFault_Handler(void);
void UsageFault_Handler(void);
void SVC_Handler(void);
void DebugMon_Handler(void);
void PendSV_Handler(void);
void SysTick_Handler(void);
/* USER CODE BEGIN EFP */
/* USER CODE END EFP */
#ifdef __cplusplus
}
#endif
#endif /* __STM32F1xx_IT_H */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Src/main.c
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 "usart.h"
#include "gpio.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <string.h>
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
uint8_t UART_Recv[5]; /* 接收 4 字节命令，第 5 字节保留为结束符。 */
uint8_t DHT11_Buf[30]; /* 保存待发送的格式化文本。 */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 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_USART1_UART_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
HAL_UART_Receive(&huart1, UART_Recv, 4, 1000); /* 轮询接收完整 4 字节，整次调用最多等待 1 秒。 */
if(strcmp("LED1", (char *)UART_Recv)==0)
{
HAL_GPIO_TogglePin(LED1_GPIO_Port, LED1_Pin);
memset(UART_Recv, '\0', 4);
}
if(!strcmp("LED2", (char *)UART_Recv))
{
HAL_GPIO_TogglePin(LED2_GPIO_Port, LED2_Pin);
memset(UART_Recv, '\0', 4);
}
sprintf((char *)DHT11_Buf,"H2:%f T2:%f\n",30.1,36.5);
HAL_UART_Transmit(&huart1, (char *)DHT11_Buf, strlen(DHT11_Buf), 1000);
printf("Hellow world wfeng %d!\n",123);
/* 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};
/** 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();
}
}
/* 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 */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Src/gpio.c
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file gpio.c
* @brief This file provides code for the configuration
* of all used GPIO pins.
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 "gpio.h"
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/*----------------------------------------------------------------------------*/
/* Configure GPIO */
/*----------------------------------------------------------------------------*/
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/** Configure pins as
* Analog
* Input
* Output
* EVENT_OUT
* EXTI
*/
void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOE_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(LED2_GPIO_Port, LED2_Pin, GPIO_PIN_SET);
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(LED1_GPIO_Port, LED1_Pin, GPIO_PIN_SET);
/*Configure GPIO pin : PtPin */
GPIO_InitStruct.Pin = LED2_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(LED2_GPIO_Port, &GPIO_InitStruct);
/*Configure GPIO pin : PtPin */
GPIO_InitStruct.Pin = LED1_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(LED1_GPIO_Port, &GPIO_InitStruct);
}
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Src/usart.c
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file usart.c
* @brief This file provides code for the configuration
* of the USART instances.
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 "usart.h"
/* USER CODE BEGIN 0 */
uint8_t u_buf[256];
/* USER CODE END 0 */
UART_HandleTypeDef huart1;
/* USART1 init function */
void MX_USART1_UART_Init(void)
{
/* USER CODE BEGIN USART1_Init 0 */
/* USER CODE END USART1_Init 0 */
/* USER CODE BEGIN USART1_Init 1 */
/* USER CODE END USART1_Init 1 */
huart1.Instance = USART1;
huart1.Init.BaudRate = 115200;
huart1.Init.WordLength = UART_WORDLENGTH_8B;
huart1.Init.StopBits = UART_STOPBITS_1;
huart1.Init.Parity = UART_PARITY_NONE;
huart1.Init.Mode = UART_MODE_TX_RX;
huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart1.Init.OverSampling = UART_OVERSAMPLING_16;
if (HAL_UART_Init(&huart1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USART1_Init 2 */
/* USER CODE END USART1_Init 2 */
}
void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
if(uartHandle->Instance==USART1)
{
/* USER CODE BEGIN USART1_MspInit 0 */
/* USER CODE END USART1_MspInit 0 */
/* USART1 clock enable */
__HAL_RCC_USART1_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/**USART1 GPIO Configuration
PA9 ------> USART1_TX
PA10 ------> USART1_RX
*/
GPIO_InitStruct.Pin = GPIO_PIN_9;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
GPIO_InitStruct.Pin = GPIO_PIN_10;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* USER CODE BEGIN USART1_MspInit 1 */
/* USER CODE END USART1_MspInit 1 */
}
}
void HAL_UART_MspDeInit(UART_HandleTypeDef* uartHandle)
{
if(uartHandle->Instance==USART1)
{
/* USER CODE BEGIN USART1_MspDeInit 0 */
/* USER CODE END USART1_MspDeInit 0 */
/* Peripheral clock disable */
__HAL_RCC_USART1_CLK_DISABLE();
/**USART1 GPIO Configuration
PA9 ------> USART1_TX
PA10 ------> USART1_RX
*/
HAL_GPIO_DeInit(GPIOA, GPIO_PIN_9|GPIO_PIN_10);
/* USER CODE BEGIN USART1_MspDeInit 1 */
/* USER CODE END USART1_MspDeInit 1 */
}
}
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* ========================================================================
* Project: CubeIDE/03UART
* File: Core/Src/stm32f1xx_it.c
* ======================================================================== */
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file stm32f1xx_it.c
* @brief Interrupt Service Routines.
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 "stm32f1xx_it.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN TD */
/* USER CODE END TD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/* External variables --------------------------------------------------------*/
/* USER CODE BEGIN EV */
/* USER CODE END EV */
/******************************************************************************/
/* Cortex-M3 Processor Interruption and Exception Handlers */
/******************************************************************************/
/**
* @brief This function handles Non maskable interrupt.
*/
void NMI_Handler(void)
{
/* USER CODE BEGIN NonMaskableInt_IRQn 0 */
/* USER CODE END NonMaskableInt_IRQn 0 */
/* USER CODE BEGIN NonMaskableInt_IRQn 1 */
while (1)
{
}
/* USER CODE END NonMaskableInt_IRQn 1 */
}
/**
* @brief This function handles Hard fault interrupt.
*/
void HardFault_Handler(void)
{
/* USER CODE BEGIN HardFault_IRQn 0 */
/* USER CODE END HardFault_IRQn 0 */
while (1)
{
/* USER CODE BEGIN W1_HardFault_IRQn 0 */
/* USER CODE END W1_HardFault_IRQn 0 */
}
}
/**
* @brief This function handles Memory management fault.
*/
void MemManage_Handler(void)
{
/* USER CODE BEGIN MemoryManagement_IRQn 0 */
/* USER CODE END MemoryManagement_IRQn 0 */
while (1)
{
/* USER CODE BEGIN W1_MemoryManagement_IRQn 0 */
/* USER CODE END W1_MemoryManagement_IRQn 0 */
}
}
/**
* @brief This function handles Prefetch fault, memory access fault.
*/
void BusFault_Handler(void)
{
/* USER CODE BEGIN BusFault_IRQn 0 */
/* USER CODE END BusFault_IRQn 0 */
while (1)
{
/* USER CODE BEGIN W1_BusFault_IRQn 0 */
/* USER CODE END W1_BusFault_IRQn 0 */
}
}
/**
* @brief This function handles Undefined instruction or illegal state.
*/
void UsageFault_Handler(void)
{
/* USER CODE BEGIN UsageFault_IRQn 0 */
/* USER CODE END UsageFault_IRQn 0 */
while (1)
{
/* USER CODE BEGIN W1_UsageFault_IRQn 0 */
/* USER CODE END W1_UsageFault_IRQn 0 */
}
}
/**
* @brief This function handles System service call via SWI instruction.
*/
void SVC_Handler(void)
{
/* USER CODE BEGIN SVCall_IRQn 0 */
/* USER CODE END SVCall_IRQn 0 */
/* USER CODE BEGIN SVCall_IRQn 1 */
/* USER CODE END SVCall_IRQn 1 */
}
/**
* @brief This function handles Debug monitor.
*/
void DebugMon_Handler(void)
{
/* USER CODE BEGIN DebugMonitor_IRQn 0 */
/* USER CODE END DebugMonitor_IRQn 0 */
/* USER CODE BEGIN DebugMonitor_IRQn 1 */
/* USER CODE END DebugMonitor_IRQn 1 */
}
/**
* @brief This function handles Pendable request for system service.
*/
void PendSV_Handler(void)
{
/* USER CODE BEGIN PendSV_IRQn 0 */
/* USER CODE END PendSV_IRQn 0 */
/* USER CODE BEGIN PendSV_IRQn 1 */
/* USER CODE END PendSV_IRQn 1 */
}
/**
* @brief This function handles System tick timer.
*/
void SysTick_Handler(void)
{
/* USER CODE BEGIN SysTick_IRQn 0 */
/* USER CODE END SysTick_IRQn 0 */
HAL_IncTick();
/* USER CODE BEGIN SysTick_IRQn 1 */
/* USER CODE END SysTick_IRQn 1 */
}
/******************************************************************************/
/* STM32F1xx Peripheral Interrupt Handlers */
/* Add here the Interrupt Handlers for the used peripherals. */
/* For the available peripheral interrupt handler names, */
/* please refer to the startup file (startup_stm32f1xx.s). */
/******************************************************************************/
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
一、串口轮询方式接收数据原理分析
1.1 代码走读
应用调用：
HAL_UART_Receive(&huart1, UART_Recv, 4, 1000);
HAL 内部先检查接收状态、指针和长度，再记录起始 Tick，设置传输总量和剩余计数，最后进入 while (huart->RxXferCount > 0U)。每轮等待一个 RXNE 事件、从数据寄存器读取一个数据元素、移动指针并把剩余计数减 1。
返回值有四种常见可能：
| 返回值 | 含义 |
|---|---|
HAL_OK | 指定数量的数据全部收到 |
HAL_TIMEOUT | 整个等待过程超过 Timeout |
HAL_BUSY | 同一 UART 已有接收过程 |
HAL_ERROR | 参数无效或发生阻塞性错误 |
业务代码应先检查返回值，再使用缓冲区。超时时缓冲区可能已经收到部分数据，不能当作完整命令。
1.2 数据接收分析
USART 的接收电路可简化为：
RX引脚
↓ 起始位检测、按波特率采样
接收移位寄存器
↓ 一帧接收完成
USART_DR 数据寄存器 ── RXNE=1
↓ CPU读取DR
内存缓冲区 ── RXNE清除
STM32F1 的 USART_DR 中有效数据位为 DR[8:0]。代码：
*pdata8bits = (uint8_t)(huart->Instance->DR & 0x00FF);
使用按位与 & 保留低 8 位；逻辑与 && 只会得到 0 或 1，不能提取数据。读取 DR 后，硬件清除 RXNE，下一帧才能继续进入接收数据寄存器。
pdata8bits++ 让指针移动到缓冲区的下一个字节，RxXferCount-- 表示还需接收的数据元素少一个。这里的 Count 是“剩余元素数”，不是已接收数量。
1.3 p德尔塔八比特/十六比特分析
HAL 根据字长和校验配置选择 8 位或 16 位指针：
| 字长 | 校验 | 有效用户数据 | 指针/掩码 |
|---|---|---|---|
| 8 bit | 无 | 8 bit | uint8_t*，0x00FF |
| 8 bit | 有 | 7 bit + 1校验位 | uint8_t*，0x007F |
| 9 bit | 无 | 9 bit | uint16_t*，0x01FF |
| 9 bit | 有 | 8 bit + 1校验位 | uint8_t*，0x00FF |
“9 位模式”不等于每次一定接收两个完整字节。无校验的 9 位数据需要 16 位变量承载，但每个元素只有低 9 位有效。此时 Size 表示 uint16_t 元素数量，调用方也必须提供正确对齐、足够大的缓冲区。
1.4 timeout参数分析
Timeout=1000 表示最多等待约 1000 ms。HAL_UART_Receive() 只在进入函数时执行一次：
tickstart = HAL_GetTick();
随后每个字节等待都使用同一个 tickstart，所以 Timeout 覆盖的是整次接收，不是“每个字节各有 1000 ms”。如果前三个字节用了 990 ms，第四个字节只剩很短时间。
HAL 默认时间基准由 SysTick 提供：
SysTick每1 ms产生一次中断
↓
HAL_IncTick()
↓
uwTick加1
↓
HAL_GetTick()返回uwTick
使用无符号减法 HAL_GetTick() - tickstart，即使 32 位 Tick 回绕，也能在超时时间远小于一个完整回绕周期时正确计算经过时间。
1.5 hyde函数讲解
这里讨论的是 HAL_Delay()。其核心逻辑：
uint32_t tickstart = HAL_GetTick();
uint32_t wait = Delay;
wait += uwTickFreq;
while ((HAL_GetTick() - tickstart) < wait)
{
}
默认 uwTickFreq 为 1 ms，额外增加一个 Tick 是为了保证实际等待时间不少于请求值，因为函数可能在当前毫秒快结束时被调用。
HAL_Delay() 也是忙等待：CPU 不断读取 Tick。若在一个优先级高于 SysTick 的中断中调用，SysTick 可能无法抢占，uwTick 不再增长，延时会卡住。因此中断回调中不应调用 HAL_Delay()。
1.6 轮询接收数据原理分析
等待 RXNE 的关键函数调用：
UART_WaitOnFlagUntilTimeout(
huart,
UART_FLAG_RXNE,
RESET,
tickstart,
Timeout);
函数内部条件可以读成：“只要 RXNE 当前仍等于 RESET，就继续循环”：
while ((__HAL_UART_GET_FLAG(huart, Flag) ? SET : RESET) == Status)
{
if ((HAL_GetTick() - Tickstart) > Timeout)
return HAL_TIMEOUT;
}
return HAL_OK;
这里 Status 传入 RESET。RXNE 仍为 0 时循环；RXNE 变成 1 后条件不成立，返回 HAL_OK，外层函数才读取 DR。代码还会检查 ORE 溢出错误，发生阻塞性错误时终止接收。
flowchart TD
A[读取SR中的RXNE] --> B{RXNE等于RESET?}
B -- 否 --> C[返回HAL_OK]
B -- 是 --> D{Timeout为无限等待?}
D -- 是 --> A
D -- 否 --> E{经过时间大于Timeout?}
E -- 否 --> F{检测到ORE?}
F -- 否 --> A
F -- 是 --> G[清错误并返回HAL_ERROR]
E -- 是 --> H[返回HAL_TIMEOUT]
1.7 函数核心分析
完整的轮询接收链路：
1. 校验RxState、pData、Size
2. RxState = BUSY_RX
3. tickstart = HAL_GetTick()
4. RxXferCount = Size
5. 循环等待RXNE
6. 读USART_DR，按字长/校验掩码保存
7. 缓冲区指针递增，RxXferCount递减
8. 收满后RxState = READY，返回HAL_OK
9. 超时则恢复READY，返回HAL_TIMEOUT
轮询并不是“定期看一眼就去做别的事”，而是在 HAL 函数里持续查询。它适合短小、低频且允许阻塞的数据；需要同时处理其他任务时，应选择中断、DMA或非阻塞状态机。