28335输出spwm

SPWM（正弦波脉宽调制）是一种用于控制交流电机的技术，它可以产生接近于正弦波的输出信号。下面是一个基于STM32的SPWM输出程序示例：

#include "stm32f10x.h"

#define PI 3.1415926
#define SAMPLE_RATE 1000 //采样率
#define PWM_FREQ 50 //PWM频率
#define PWM_PERIOD ((uint16_t)(SystemCoreClock / (SAMPLE_RATE * 2 * PWM_FREQ)))

uint16_t sinTable[360] = {0}; //正弦表
uint16_t dutyTable[360] = {0}; //占空比表

void TIM3_Configuration(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

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

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

    TIM_OC1Init(TIM3, &TIM_OCInitStructure);
    TIM_OC2Init(TIM3, &TIM_OCInitStructure);
    TIM_OC3Init(TIM3, &TIM_OCInitStructure);
    TIM_OC4Init(TIM3, &TIM_OCInitStructure);

    TIM_Cmd(TIM3, ENABLE);
}

void generateSinTable(void)
{
    uint16_t i;
    for(i = 0; i < 360; i++)
    {
        sinTable[i] = (uint16_t)(PWM_PERIOD / 2 * (1 + sin(i * PI / 180)));
    }
}

void generateDutyTable(void)
{
    uint16_t i;
    for(i = 0; i < 360; i++)
    {
        dutyTable[i] = (uint16_t)(PWM_PERIOD * i / 360);
    }
}

int main(void)
{
    uint16_t sinIndex = 0;
    uint16_t dutyIndex = 0;

    generateSinTable();
    generateDutyTable();

    TIM3_Configuration();

    while(1)
    {
        TIM_SetCompare1(TIM3, dutyTable[dutyIndex]);
        TIM_SetCompare2(TIM3, dutyTable[dutyIndex]);
        TIM_SetCompare3(TIM3, dutyTable[dutyIndex]);
        TIM_SetCompare4(TIM3, sinTable[sinIndex]);

        sinIndex++;
        if(sinIndex >= 360)
        {
            sinIndex = 0;
            dutyIndex++;
            if(dutyIndex >= 360)
            {
                dutyIndex = 0;
            }
        }

        delay_us(1000000 / SAMPLE_RATE);
    }
}

void delay_us(uint32_t nTime)
{
    uint32_t i;

    SysTick->LOAD = nTime * 9;
    SysTick->VAL = 0;
    SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk;

    for(i = 0; i < nTime; i++)
    {
        while(!(SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk));
    }

    SysTick->CTRL = 0;
}

这个程序使用TIM3输出4路PWM信号，其中3路占空比相同，1路输出正弦波。每次更新占空比和正弦波的值时，通过增加索引值来访问预先生成的占空比表和正弦表。程序使用SysTick延时函数来控制采样率。