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PWM合成正弦波#xff0c;原理什么的不详细说了#xff0c;概括一下就是 PWM有效面积的积分 正弦波的有效面积。PWM的频率越快#xff0c;细分的越多#xff0c;锯齿也就越不明显。
做法是#xff1a;首先利用正弦波取点软件#xff0c;取点1000个#xff0c;生…前言
PWM合成正弦波原理什么的不详细说了概括一下就是 PWM有效面积的积分 正弦波的有效面积。PWM的频率越快细分的越多锯齿也就越不明显。
做法是首先利用正弦波取点软件取点1000个生成一个正弦波的数组。
PWM波的频率(F_PWM)与正弦波频率(F_SIN)之间的对应关系与采样点数S_NUM有着密切的关系即: F_SINF_PWM/S_NUM S_NUM 在这里为1000因为取了1000个点
先用TIM1高级定时器来生成一个PWM波作为载波我用的是72M主频分频系数0TIM_Period填1000这个1000就是PWM的总周期要大于等于正弦波数组的满值
再用TIM2来生成一段与正弦波能量等效的PWM载波 TIM2配置的是 分频系数0计数值1440得到TIM2的频率72M/分频1(即分频器实际的分频为 分频系数1)/1440 50000Hz 即20us进入一次中断。
根据公式可以计算出F_SINF_PWM/S_NUM50000Hz/100050Hz
先上代码
#include stm32f10x.h
#include bsp_rcc.h
#include bsp_tim.h
#include bsp_AdvanceTim.hint size1000;
uint16_t sin_value[]
{500,503,506,509,512,515,518,521,525,528,531,534,537,540,543,547,550,553,556,559,562,565,568,572,575,578,581,584,587,590,593,596,599,602,606,609,612,615,618,621,624,627,630,633,636,639,642,645,648,651,654,657,660,663,666,669,672,675,678,681,684,686,689,692,695,698,701,704,707,710,712,715,718,721,724,726,729,732,735,738,740,743,746,749,751,754,757,759,762,765,767,770,773,775,778,781,783,786,788,791,793,796,798,801,803,806,808,811,813,816,818,821,823,825,828,830,833,835,837,839,842,844,846,849,851,853,855,857,860,862,864,866,868,870,872,875,877,879,881,883,885,887,889,891,893,895,896,898,900,902,904,906,908,909,911,913,915,917,918,920,922,923,925,927,928,930,931,933,935,936,938,939,941,942,944,945,946,948,949,951,952,953,955,956,957,958,960,961,962,963,964,966,967,968,969,970,971,972,973,974,975,976,977,978,979,980,981,981,982,983,984,985,985,986,987,987,988,989,989,990,991,991,992,992,993,993,994,994,995,995,996,996,996,997,997,997,998,998,998,998,999,999,999,999,999,999,999,999,999,999,1000,999,999,999,999,999,999,999,999,999,999,998,998,998,998,997,997,997,996,996,996,995,995,994,994,993,993,992,992,991,991,990,989,989,988,987,987,986,985,985,984,983,982,981,981,980,979,978,977,976,975,974,973,972,971,970,969,968,967,966,964,963,962,961,960,958,957,956,955,953,952,951,949,948,946,945,944,942,941,939,938,936,935,933,931,930,928,927,925,923,922,920,918,917,915,913,911,909,908,906,904,902,900,898,896,895,893,891,889,887,885,883,881,879,877,875,872,870,868,866,864,862,860,857,855,853,851,849,846,844,842,839,837,835,833,830,828,825,823,821,818,816,813,811,808,806,803,801,798,796,793,791,788,786,783,781,778,775,773,770,767,765,762,759,757,754,751,749,746,743,740,738,735,732,729,726,724,721,718,715,712,710,707,704,701,698,695,692,689,686,684,681,678,675,672,669,666,663,660,657,654,651,648,645,642,639,636,633,630,627,624,621,618,615,612,609,606,602,599,596,593,590,587,584,581,578,575,572,568,565,562,559,556,553,550,547,543,540,537,534,531,528,525,521,518,515,512,509,506,503,500,496,493,490,487,484,481,478,474,471,468,465,462,459,456,452,449,446,443,440,437,434,431,427,424,421,418,415,412,409,406,403,400,397,393,390,387,384,381,378,375,372,369,366,363,360,357,354,351,348,345,342,339,336,333,330,327,324,321,318,315,313,310,307,304,301,298,295,292,289,287,284,281,278,275,273,270,267,264,261,259,256,253,250,248,245,242,240,237,234,232,229,226,224,221,218,216,213,211,208,206,203,201,198,196,193,191,188,186,183,181,178,176,174,171,169,166,164,162,160,157,155,153,150,148,146,144,142,139,137,135,133,131,129,127,124,122,120,118,116,114,112,110,108,106,104,103,101,99,97,95,93,91,90,88,86,84,82,81,79,77,76,74,72,71,69,68,66,64,63,61,60,58,57,55,54,53,51,50,48,47,46,44,43,42,41,39,38,37,36,35,33,32,31,30,29,28,27,26,25,24,23,22,21,20,19,18,18,17,16,15,14,14,13,12,12,11,10,10,9,8,8,7,7,6,6,5,5,4,4,3,3,3,2,2,2,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,3,3,3,4,4,5,5,6,6,7,7,8,8,9,10,10,11,12,12,13,14,14,15,16,17,18,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,35,36,37,38,39,41,42,43,44,46,47,48,50,51,53,54,55,57,58,60,61,63,64,66,68,69,71,72,74,76,77,79,81,82,84,86,88,90,91,93,95,97,99,101,103,104,106,108,110,112,114,116,118,120,122,124,127,129,131,133,135,137,139,142,144,146,148,150,153,155,157,160,162,164,166,169,171,174,176,178,181,183,186,188,191,193,196,198,201,203,206,208,211,213,216,218,221,224,226,229,232,234,237,240,242,245,248,250,253,256,259,261,264,267,270,273,275,278,281,284,287,289,292,295,298,301,304,307,310,313,315,318,321,324,327,330,333,336,339,342,345,348,351,354,357,360,363,366,369,372,375,378,381,384,387,390,393,397,400,403,406,409,412,415,418,421,424,427,431,434,437,440,443,446,449,452,456,459,462,465,468,471,474,478,481,484,487,490,493,496
};int main(void)
{GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable,ENABLE);rcc_systempclock_init( RCC_PLLMul_9 ); //9倍频,时钟总线为72MhzAdvanceTim_GPIO_Config(); //初始化高级定时器出PWM波的GPIOAdvanceTim_Mode_Config(); //初始化高级定时器,用来产生载波TIM2_NVIC_Config(); //TIM2的中断优先级timer2_init(); //初始化TIM2用来改变载波while(1){}
}
bsp_AdvanceTim.c的内容如下
#include bsp_AdvanceTim.hvoid AdvanceTim_GPIO_Config(void)
{RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);// RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE);GPIO_InitTypeDef GPIO_InitStruct;GPIO_InitStruct.GPIO_Pin GPIO_Pin_8;GPIO_InitStruct.GPIO_Mode GPIO_Mode_AF_PP;GPIO_InitStruct.GPIO_Speed GPIO_Speed_50MHz;GPIO_Init(GPIOA,GPIO_InitStruct);
}void AdvanceTim_Mode_Config(void)
{TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; //配置时基结构体,声明一个结构体变量方便传参TIM_OCInitTypeDef TIM_OCInitStructure; //配置输出比较结构体,声明一个结构体变量方便传参//TIM_BDTRInitTypeDef TIM_BDTRInitStructure; //配置有关刹车和死区结构体,声明一个结构体变量方便传参//时基初始化//RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1,ENABLE); //开TIMER1外设时钟TIM_TimeBaseStructure.TIM_Prescaler 0;// 计数器计数模式TIM_TimeBaseStructure.TIM_CounterMode TIM_CounterMode_Up;TIM_TimeBaseStructure.TIM_Period 1000;// 时钟分频因子 - 一分频,配置死区时间需要用到TIM_TimeBaseStructure.TIM_ClockDivision TIM_CKD_DIV4;// 重复寄存器的值,没有用到,不管TIM_TimeBaseStructure.TIM_RepetitionCounter 0;TIM_TimeBaseInit(TIM1,TIM_TimeBaseStructure);////TIM_OCInitStructure.TIM_OCMode TIM_OCMode_PWM1; //PWM模式1TIM_OCInitStructure.TIM_OutputState TIM_OutputState_Enable; //TIM1通道1输出使能TIM_OCInitStructure.TIM_OutputNState TIM_OutputNState_Disable; //互补通道使能TIM_OCInitStructure.TIM_Pulse 0; //占空比TIM_OCInitStructure.TIM_OCPolarity TIM_OCPolarity_High; //高电平有效TIM_OCInitStructure.TIM_OCNPolarity TIM_OCPolarity_High; //互补通道也是高电平有效TIM_OCInitStructure.TIM_OCIdleState TIM_OCIdleState_Reset; //空闲状态 低电平TIM_OCInitStructure.TIM_OCNIdleState TIM_OCNIdleState_Reset; //互补通道空闲状态 低电平TIM_OC1Init(TIM1,TIM_OCInitStructure); //初始化TIM1通道1输出PWMTIM_OC1PreloadConfig(TIM1,TIM_OCPreload_Enable); //使能TIM1 输出比较1的预装载使能 想要改变占空比 得先输出完当前周期的波形之后 到下个波形才按照新的占空比(更新事件发生后才改变占空比)TIM_Cmd(TIM1,ENABLE);TIM_CtrlPWMOutputs(TIM1,ENABLE);
}
bsp_tim.c的内容如下
#include bsp_tim.hvoid TIM2_NVIC_Config(void)
{NVIC_InitTypeDef NVIC_InitStruct;NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);NVIC_InitStruct.NVIC_IRQChannel TIM2_IRQn;NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority 0;NVIC_InitStruct.NVIC_IRQChannelSubPriority 3;NVIC_InitStruct.NVIC_IRQChannelCmd ENABLE;NVIC_Init(NVIC_InitStruct);
}void timer2_init(void)
{TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);TIM_TimeBaseStructure.TIM_Prescaler 0;// 计数器计数模式TIM_TimeBaseStructure.TIM_CounterMode TIM_CounterMode_Up;// 自动重装载寄存器的值 填入10000 实际上会计数100001次 因为10000需要-- 10001次才能发生下溢TIM_TimeBaseStructure.TIM_Period 1440-1;// 时钟分频因子,配置死区时间需要用到TIM_TimeBaseStructure.TIM_ClockDivision TIM_CKD_DIV1;// 重复寄存器的值,没有用到,不管TIM_TimeBaseStructure.TIM_RepetitionCounter 0;TIM_TimeBaseInit(TIM2,TIM_TimeBaseStructure);// 清楚TIM2上溢中断标志位TIM_ClearFlag(TIM2,TIM_FLAG_Update);// 使能TIM2上溢中断TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);// 开启TIM2TIM_Cmd(TIM2,ENABLE);}void timer2_it_init(void)
{TIM2_NVIC_Config();timer2_init();
}这个代码输出的效果就是PA8引脚输出PWM波形但是这个波形还需要通过一个低通滤波器之后才能看到正弦波的波形。 电路如下 在箭头处挂示波器可以观察到正弦波的波形。
代码的原理就类似红外遥控那种载波频率如果很高那么合成出来的正弦波的锯齿就越不明显。同时TIM2的频率也十分重要他决定了正弦波的频率。
举例来说 比如我现在要生成50Hz的正弦波那么我取了1000个点也就意味着在50Hz即20ms这个总周期内我需要跑完数组的1000个点那么20ms/1000 20us ,所以TIM2的中断时间就必须是20us。
每隔20usTIM2进入中断服务函数查表之后把TIM1生成的PWM的占空比更新一次在没到20us这段期间PWM还是按照当前的占空比不断输出所以TIM1的频率越高每20us中含有的方波数就越多精度也就越高锯齿就会越细。当到达20us之后更新占空比PWM又按照新的占空比去输出波形。当数组1000个内容输出完之后一个完整的正弦波就出来了但是要注意的是这个正弦波没有负半周(以GND为参考点的话)因为我们的MCU输出不了负电压。
这个正弦波完整输出一次的时间就是20us(占空比改变一次)*1000(个点) 20000us 20ms 即50Hz。
我个人理解的基本原理就是这样如果有误欢迎指出。
