stm32+US-100例程代码

以下是STM32与US-100超声波模块的例程代码：

#include "stm32f10x.h"
#include "usart.h"
#include "delay.h"

#define TRIG GPIO_Pin_1
#define ECHO GPIO_Pin_2

void GPIO_Configuration(void);
void TIM2_Configuration(void);
float Get_distance(void);
void USART_SendString(USART_TypeDef* USARTx, char* s);

int main(void)
{
    GPIO_Configuration();
    TIM2_Configuration();
    USART_Configuration();
    delay_init();
    
    float distance;
    char str[20];
    
    while(1)
    {
        distance = Get_distance();
        sprintf(str, "Distance: %.2fcm\r\n", distance);
        USART_SendString(USART1, str);
        delay_ms(500);
    }
}

void GPIO_Configuration(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    
    GPIO_InitStructure.GPIO_Pin = TRIG;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    GPIO_InitStructure.GPIO_Pin = ECHO;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
}

void TIM2_Configuration(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    
    TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1;
    TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
    
    TIM_Cmd(TIM2, ENABLE);
}

float Get_distance(void)
{
    float distance;
    uint16_t value;
    GPIO_SetBits(GPIOA, TRIG);
    delay_us(10);
    GPIO_ResetBits(GPIOA, TRIG);
    
    while(GPIO_ReadInputDataBit(GPIOA, ECHO) == RESET);
    TIM_SetCounter(TIM2, 0);
    while(GPIO_ReadInputDataBit(GPIOA, ECHO) == SET);
    value = TIM_GetCounter(TIM2);
    
    distance = (float)value / 58.0;
    return distance;
}

void USART_SendString(USART_TypeDef* USARTx, char* s)
{
    while(*s)
    {
        while(USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET);
        USART_SendData(USARTx, (uint16_t)(*s++));
    }
}

使用该例程代码，需要先初始化GPIO引脚和定时器TIM2，然后在主函数中调用`Get_distance()`函数获取超声波测距的距离值，最后使用串口发送函数`USART_SendString()`将距离值发送到计算机上。