红外遥控原理分析

遥控  ：NEC 编码  960nm的波长  晶振为455KHZ，对应的发射频率(载波频率)为38KHZ，
遥控ID为0(即系统识别码)，反码为255，不同的遥控ID有可能不一样。

遥控码由三部分组成
1、leader code   9ms的高电平 + 4.5ms 的低电平
2、系统识别码    区别不同的红外遥控设备
3、操作码        8bit操作码和8bit的操作反码组成

发送方的电平跟接收方解调出来的电平是反向的。
红外接收头接收到遥控器的信号后，解码出后的数据格式如下：
写程序即根据这个信号的格式来写。
__________________               _______   _   _   _   _   _   _   _   _   ____   ____   ____   ____   ____   ____   ____   ____                                 ___________________________________               _______   ___________________________________________________________
|_____________|       |_| |_| |_| |_| |_| |_| |_| |_| |_|    |_|    |_|    |_|    |_|    |_|    |_|    |_|    |x x x x x x x x|x x x x x x x x|                                   |_____________|       |_|                                                                    
|<-    9ms  ->|<4.5ms>|
|----leader code------|-----custom code 8bit----------|-----------------custom code' 8bit---------------------| key data 8bit |key data'8bit  |<---------------40ms---------------><----9ms-----><2.1ms>--|--------------- 此时的高电平超过40ms,然后出现9ms的低电平，2.1ms的高电平 连发码----------------

0和1均以0.56ms的低电平开始(实际测量是500us的样子)，不同的是后面出现的高电平，
如果高电平是0.56ms(实际测量是500us的样子)，则表示0，如果高电平是1.68ms(0.56*3=1.68)则表示1
0.56ms:|_|
_   _   _ 
0:     |_| |_| |
_   ____   ____  
1:     |_|    |_|    |_

写代码的时候只需要检测高电平的时间即可。
以下时间都是通过示波器实际测量所得。
引导码的高电平：4.5ms
0的高电平     ：0.56ms(实测0.5ms的样子)
1的高电平     ：1.68ms
连发码的高电平：2.1ms

NEC码分析

代码展示：

/* USER CODE BEGIN Header */
/********************************************************************************* @file           : main.c* @brief          : Main program body******************************************************************************* @attention** <h2><center>&copy; Copyright (c) 2020 STMicroelectronics.* All rights reserved.</center></h2>** This software component is licensed by ST under BSD 3-Clause license,* the "License"; You may not use this file except in compliance with the* License. You may obtain a copy of the License at:*                        opensource.org/licenses/BSD-3-Clause********************************************************************************/
/* USER CODE END Header *//* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "usart.h"
#include "gpio.h"/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
/* USER CODE END Includes *//* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD *//* USER CODE END PTD *//* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
#define IR_IN  HAL_GPIO_ReadPin(GPIOB,GPIO_PIN_0)
/* USER CODE END PD *//* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM *//* USER CODE END PM *//* Private variables ---------------------------------------------------------*//* USER CODE BEGIN PV */
uint32_t Remote_Order = 0;
uint8_t Remote_Count = 0 ;
uint8_t Remote_Reday = 0 ;
/* USER CODE END PV *//* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
uint8_t Pulse_Width_Check(void);
uint8_t Remote_Process(void);void delay_us(int32_t nus){int32_t temp;SysTick->LOAD = nus*6 ; //32MHzSysTick->VAL=0X00;//清空计数SysTick->CTRL=0X01;//使能，减到零是无动作，采用外部时钟源do{temp=SysTick->CTRL;//读取当前倒计时}while((temp&0x01)&&(!(temp&(1<<16))));//等待时间到达SysTick->CTRL=0x00; //关闭计数SysTick->VAL =0X00; //清空计数}
/* 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){/* USER CODE END WHILE *//* USER CODE BEGIN 3 */HAL_GPIO_TogglePin(red_GPIO_Port,red_Pin);//  printf("order-code \r\n");if(Remote_Reday){uint8_t key = Remote_Process();printf("order-code =  %08X , key-code = %02X \r\n",Remote_Order,key);}}/* 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 CPU, AHB and APB busses clocks */RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;RCC_OscInitStruct.HSIState = RCC_HSI_ON;RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL12;RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK){Error_Handler();}/** Initializes the CPU, AHB and APB busses clocks */RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK|RCC_CLOCKTYPE_PCLK1;RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK){Error_Handler();}PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART1;PeriphClkInit.Usart1ClockSelection = RCC_USART1CLKSOURCE_PCLK1;if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK){Error_Handler();}
}/* USER CODE BEGIN 4 */#ifdef __GNUC__/* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printfset to 'Yes') calls __io_putchar() */#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ */
/*** @brief  Retargets the C library printf function to the USART.* @param  None* @retval None*/
PUTCHAR_PROTOTYPE
{/* Place your implementation of fputc here *//* e.g. write a character to the EVAL_COM1 and Loop until the end of transmission */HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xFFFF);return ch;
}
// 脉冲处理uint8_t Pulse_Width_Check(void)
{uint8_t t=0;while(IR_IN == GPIO_PIN_SET){t ++ ;delay_us(20);if(t==250) return t;}return t;
}
// 外部中断的回调函数void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{uint8_t res = 0 ;uint8_t OK = 0;uint8_t temp = 0;if(GPIO_Pin & GPIO_PIN_0){while(1){if(IR_IN == GPIO_PIN_SET){res = Pulse_Width_Check(); // 脉宽测量if(res == 250) break;else if(res >= 200 && res < 250)  OK = 1;else if(res >= 85 && res < 200){Remote_Reday = 1;Remote_Count ++;break;}else if(res >= 50 && res < 85) temp = 1;else if(res >= 10 && res < 50) temp = 0;if(OK){Remote_Order <<=1;Remote_Order += temp;Remote_Count = 0;}}}}
}// 解码处理uint8_t Remote_Process(void)
{uint8_t t1 ,t2 ;t1 = Remote_Order >> 24 ;t2 = (Remote_Order >> 16) & 0xFF ;Remote_Reday = 0;if(t1 ==(uint8_t) ~t2){t1 = Remote_Order >> 8;t2 = Remote_Order ;if(t1 ==(uint8_t) ~ t2) return t1;}return 0;
}/* 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 *//* 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(char *file, uint32_t line)
{ /* USER CODE BEGIN 6 *//* User can add his own implementation to report the file name and line number,tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) *//* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT *//************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/