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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 offOled_Write_Cmd(0x00);//---set low column addressOled_Write_Cmd(0x10);//---set high column addressOled_Write_Cmd(0x40);//--set start line address  Oled_Write_Cmd(0xB0);//--set page addressOled_Write_Cmd(0x81); // contract controlOled_Write_Cmd(0xFF);//--128   Oled_Write_Cmd(0xA1);//set segment remap Oled_Write_Cmd(0xA6);//--normal / reverseOled_Write_Cmd(0xA8);//--set multiplex ratio(1 to 64)Oled_Write_Cmd(0x3F);//--1/32 dutyOled_Write_Cmd(0xC8);//Com scan directionOled_Write_Cmd(0xD3);//-set display offsetOled_Write_Cmd(0x00);//Oled_Write_Cmd(0xD5);//set osc divisionOled_Write_Cmd(0x80);//Oled_Write_Cmd(0xD8);//set area color mode offOled_Write_Cmd(0x05);//Oled_Write_Cmd(0xD9);//Set Pre-Charge PeriodOled_Write_Cmd(0xF1);//Oled_Write_Cmd(0xDA);//set com pin configuartionOled_Write_Cmd(0x12);//Oled_Write_Cmd(0xDB);//set VcomhOled_Write_Cmd(0x30);//Oled_Write_Cmd(0x8D);//set charge pump enableOled_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 modeOled_Write_Cmd (0x02);                    //page addressing modefor(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*2-2unsigned int  i;Oled_Write_Cmd(0xb0+(row*2-2));                           //page 0Oled_Write_Cmd(0x00+(col&0x0f));                          //lowOled_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 1Oled_Write_Cmd(0x00+(col&0x0f));                          //lowOled_Write_Cmd(0x10+(col>>4));                            //highfor(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1cmOled_Show_Str(2,2,speedMes);speedCnt = 0;
}