解释这行代码#ifndef _flash_h_ #define _flash_h 1

这行代码是条件编译预处理指令，用于防止头文件的重复包含。让我来解释它的含义：

1. `#ifndef _flash_h_` 检查名为 `_flash_h_` 的宏是否未定义。如果未定义，则表示该头文件尚未被包含。

2. `#define _flash_h_ 1` 定义名为 `_flash_h_` 的宏，并将其值设置为 1。这样做的目的是标记该头文件已被包含，以防止重复包含。

通过使用条件编译预处理指令，可以确保头文件只被包含一次，避免引起编译错误或重复定义的问题。这是一种常见的头文件保护机制，在编写复杂程序时很有用。

相关问题

system_stm32f10x.h头文件的代码

以下是 `system_stm32f10x.h` 头文件的代码：

/**
  ******************************************************************************
  * @file    system_stm32f10x.h
  * @author  MCD Application Team
  * @version V3.6.1
  * @date    22-April-2016
  * @brief   CMSIS Cortex-M3 Device Peripheral Access Layer System Header File.
  *          This file contains the system clock configuration for STM32F10x devices,
  *          and is customized for use with STM32F103 devices.
  ******************************************************************************
  * @copyright (c) 2016 STMicroelectronics
  * @author MCD
  * @brief Header for system_stm32f10x.c module
  ******************************************************************************
  */

#ifndef __SYSTEM_STM32F10X_H
#define __SYSTEM_STM32F10X_H

#ifdef __cplusplus
extern "C" {
#endif

#include <stdint.h>

extern uint32_t SystemCoreClock;

/**
  * @brief  Setup the microcontroller system
  *         Initialize the Embedded Flash Interface, the PLL and update the
  *         SystemCoreClock variable.
  * @note   This function should be used only after reset.
  * @param  None
  * @retval None
  */
void SystemInit(void);

/**
  * @brief  Update SystemCoreClock variable according to Clock Register Values.
  *         The SystemCoreClock variable contains the core clock (HCLK), it can
  *         be used by the user application to setup the SysTick timer or configure
  *         other parameters.
  * @note   None
  * @param  None
  * @retval None
  */
void SystemCoreClockUpdate(void);

#ifdef __cplusplus
}
#endif

#endif /* __SYSTEM_STM32F10X_H */

该文件定义了 `SystemInit()` 和 `SystemCoreClockUpdate()` 函数，并声明了一个名为 `SystemCoreClock` 的全局变量。这些函数和变量用于设置和更新系统时钟。

基于HAL库的stm32f103rct6 MAX6675 .C和.H的完整HAL库程序

以下是基于HAL库的stm32f103rct6和MAX6675的完整程序，包含了对应的.C和.H文件。请注意，此程序仅供参考，具体实现可能需要根据您的硬件和软件环境进行修改。

MAX6675.h

#ifndef __MAX6675_H
#define __MAX6675_H

#include "stm32f1xx_hal.h"

#define CS_PORT GPIOA
#define CS_PIN GPIO_PIN_1

#define SCK_PORT GPIOA
#define SCK_PIN GPIO_PIN_5

#define SO_PORT GPIOA
#define SO_PIN GPIO_PIN_6

void MAX6675_Init(void);
float MAX6675_Read_Temperature(void);

#endif

MAX6675.c

#include "MAX6675.h"

/* Private variables ---------------------------------------------------------*/
SPI_HandleTypeDef hspi1;

/* Private function prototypes -----------------------------------------------*/
void MAX6675_SPI_Init(void);

void MAX6675_Init(void)
{
  MAX6675_SPI_Init();

  HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);
}

float MAX6675_Read_Temperature(void)
{
  uint8_t i;
  uint8_t buffer[2];
  uint16_t value;

  HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_RESET);

  HAL_SPI_Receive(&hspi1, buffer, 2, HAL_MAX_DELAY);

  HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);

  value = ((uint16_t)buffer[0] << 8) | buffer[1];

  if (value & 0x4)
  {
    return -1000.0f;
  }

  value >>= 3;

  return (float)value * 0.25f;
}

void MAX6675_SPI_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* SPI1 GPIO Configuration */
  /* PA5     ------> SPI1_SCK */
  /* PA6     ------> SPI1_MISO */
  /* PA7     ------> SPI1_MOSI */
  GPIO_InitStruct.Pin = SCK_PIN | SO_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = CS_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(CS_PORT, &GPIO_InitStruct);

  __HAL_RCC_SPI1_CLK_ENABLE();

  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_0;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 10;
  HAL_SPI_Init(&hspi1);
}

main.c

#include "main.h"
#include "MAX6675.h"
#include <stdio.h>

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI1_Init(void);

int main(void)
{
  float temperature;

  HAL_Init();

  SystemClock_Config();

  MX_GPIO_Init();
  MX_SPI1_Init();

  MAX6675_Init();

  while (1)
  {
    temperature = MAX6675_Read_Temperature();

    if (temperature == -1000.0f)
    {
      printf("Thermocouple is not connected!\r\n");
    }
    else
    {
      printf("Temperature: %.2f C\r\n", temperature);
    }

    HAL_Delay(1000);
  }
}

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.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();
  }
}

static void MX_SPI1_Init(void)
{
  /* 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_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
  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();
  }
}

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOA_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(CS_PORT, CS_PIN, GPIO_PIN_SET);

  /*Configure GPIO pin : CS_Pin */
  GPIO_InitStruct.Pin = CS_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(CS_PORT, &GPIO_InitStruct);
}