基于50MHz时钟编写的180度舵机控制程序

此处提供一个基于50MHz时钟编写的180度舵机控制程序的示例代码，供参考：

#include "stm32f10x.h"

#define PWM_PERIOD 20000

void SysTick_Handler(void)
{
static uint32_t counter = 0;
static uint32_t angle = 0;

if(++counter >= 10000) // 200ms
{
counter = 0;

if(++angle > 180)
{
angle = 0;
}

TIM_SetCompare1(TIM3, angle * PWM_PERIOD / 180 + 1000); // 1ms~2ms
}
}

int main(void)
{
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_TimeBaseStructure.TIM_Period = PWM_PERIOD - 1;
TIM_TimeBaseStructure.TIM_Prescaler = 49;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_Pulse = 1000; // 1ms
TIM_OC1Init(TIM3, &TIM_OCInitStructure);

TIM_Cmd(TIM3, ENABLE);
TIM_CtrlPWMOutputs(TIM3, ENABLE);

SysTick_Config(SystemCoreClock / 10000); // 100us

while(1);
}

该程序使用SysTick定时器中断来控制舵机旋转角度，每200ms改变一次角度。舵机的控制信号使用TIM3的PWM输出，输出频率为50MHz/50=1MHz，占空比范围为1ms~2ms，即舵机的角度范围为0度~180度。在每次角度变化时，根据角度计算出对应的占空比，并设置到TIM3的PWM输出中。需要注意的是，舵机的控制信号一般需要在1ms~2ms范围内变化，占空比超出这个范围可能会导致舵机损坏。因此在计算占空比时需要加上一个偏移量，确保占空比始终在安全范围内。