目录

1. 测速模块

2. 测试原理和单位换算

3. 定时器和中断实现测速开发和调试代码

4. 小车速度显示在OLED屏

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1. 测速模块

• 用途：广泛用于电机转速检测，脉冲计数,位置限位等。
• 有遮挡，输出高电平；无遮挡，输出低电平
• 接线 :VCC 接电源正极3.3-5V
• GND 接电源负极 DO TTL开关信号输出
• AO 此模块不起作用

2. 测试原理和单位换算

• 轮子走一圈，经过一个周长，C = 2x3.14x半径= 3.14 x 直径（6.5cm）
• 对应的码盘也转了一圈，码盘有20个格子，每经过一个格子，会遮挡（高电平）和不遮挡（低电平）， 那么一个脉冲就是走了 3.14 * 6.5 cm /20 = 1.0205CM
• 定时器可以设计成一秒，统计脉冲数，一个脉冲就是1cm
• 假设一秒有80脉冲，那么就是80cm/s

3. 定时器和中断实现测速开发和调试代码

测试数据通过串口发送到上位机

硬件接线

测速模块：

• VCC -- 3.3V 不能接5V，否则遮挡一次会触发3次中断
• OUT -- PB14

cubeMX配置

代码实现：

unsigned int speedCnt;

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
    if (GPIO_Pin == GPIO_PIN_14)
        if (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_14) == GPIO_PIN_RESET)
            speedCnt++;
}
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    printf("speed: %d\r\n", speedCnt);
    speedCnt = 0;
}

main函数里：
HAL_TIM_Base_Start_IT(&htim2);

4. 小车速度显示在OLED屏

OLED模块介绍：STM32 OLED屏幕显示详解

硬件接线

• SCL -- PB6
• SDA -- PB7

代码示例：

oled.c

#include "oled.h"
#include "i2c.h"
#include "oledfont.h"

void Oled_Write_Cmd(uint8_t dataCmd)
{
	
	HAL_I2C_Mem_Write(&hi2c1, 0x78, 0x00, I2C_MEMADD_SIZE_8BIT,
										&dataCmd, 1, 0xff);
}

void Oled_Write_Data(uint8_t dataData)
{
	HAL_I2C_Mem_Write(&hi2c1, 0x78, 0x40, I2C_MEMADD_SIZE_8BIT,
										&dataData, 1, 0xff);
}

void Oled_Init(void){
	Oled_Write_Cmd(0xAE);//--display off
	Oled_Write_Cmd(0x00);//---set low column address
	Oled_Write_Cmd(0x10);//---set high column address
	Oled_Write_Cmd(0x40);//--set start line address  
	Oled_Write_Cmd(0xB0);//--set page address
	Oled_Write_Cmd(0x81); // contract control
	Oled_Write_Cmd(0xFF);//--128   
	Oled_Write_Cmd(0xA1);//set segment remap 
	Oled_Write_Cmd(0xA6);//--normal / reverse
	Oled_Write_Cmd(0xA8);//--set multiplex ratio(1 to 64)
	Oled_Write_Cmd(0x3F);//--1/32 duty
	Oled_Write_Cmd(0xC8);//Com scan direction
	Oled_Write_Cmd(0xD3);//-set display offset
	Oled_Write_Cmd(0x00);//
	
	Oled_Write_Cmd(0xD5);//set osc division
	Oled_Write_Cmd(0x80);//
	
	Oled_Write_Cmd(0xD8);//set area color mode off
	Oled_Write_Cmd(0x05);//
	
	Oled_Write_Cmd(0xD9);//Set Pre-Charge Period
	Oled_Write_Cmd(0xF1);//
	
	Oled_Write_Cmd(0xDA);//set com pin configuartion
	Oled_Write_Cmd(0x12);//
	
	Oled_Write_Cmd(0xDB);//set Vcomh
	Oled_Write_Cmd(0x30);//
	
	Oled_Write_Cmd(0x8D);//set charge pump enable
	Oled_Write_Cmd(0x14);//
	
	Oled_Write_Cmd(0xAF);//--turn on oled panel		
}

void Oled_Screen_Clear(void){
	char i,n;
	Oled_Write_Cmd (0x20);                    //set memory addressing mode
	Oled_Write_Cmd (0x02);                    //page addressing mode

	for(i=0;i<8;i++){
		Oled_Write_Cmd(0xb0+i);               
		Oled_Write_Cmd(0x00);                 
		Oled_Write_Cmd(0x10);                 
		for(n=0;n<128;n++)Oled_Write_Data(0x00); 			
	}	
}

void Oled_Show_Char(char row,char col,char oledChar){ //row*2-2
	unsigned int  i;
	Oled_Write_Cmd(0xb0+(row*2-2));                           //page 0
	Oled_Write_Cmd(0x00+(col&0x0f));                          //low
	Oled_Write_Cmd(0x10+(col>>4));                            //high	
	for(i=((oledChar-32)*16);i<((oledChar-32)*16+8);i++){
		Oled_Write_Data(F8X16[i]);                            //写数据oledTable1
	}

	Oled_Write_Cmd(0xb0+(row*2-1));                           //page 1
	Oled_Write_Cmd(0x00+(col&0x0f));                          //low
	Oled_Write_Cmd(0x10+(col>>4));                            //high
	for(i=((oledChar-32)*16+8);i<((oledChar-32)*16+8+8);i++){
		Oled_Write_Data(F8X16[i]);                            //写数据oledTable1
	}		
}


/******************************************************************************/
// 函数名称：Oled_Show_Char 
// 输入参数：oledChar 
// 输出参数：无 
// 函数功能：OLED显示单个字符
/******************************************************************************/
void Oled_Show_Str(char row,char col,char *str){
	while(*str!=0){
		Oled_Show_Char(row,col,*str);
		str++;
		col += 8;	
	}		
}

main.c

extern uint8_t buf;
unsigned int speedCnt = 0;
char speedMes[24];  //主程序发送速度数据的字符串缓冲区

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
	if (GPIO_Pin == GPIO_PIN_14)
		if (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_14) == GPIO_PIN_RESET)
			speedCnt++;
}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
	printf("speed: %d\r\n", speedCnt);
	sprintf(speedMes,"speed:%2d cm/s",speedCnt);//串口数据的字符串拼装，speed是格子，每个格子1cm
	Oled_Show_Str(2,2,speedMes);
	speedCnt = 0;
}