下面代码中，用定时器控制ADC的采样率有什么好处吗？另外，为什么采样率要设置为40KHz？
//arr:定时器周期
//psc:预分频器数值 计数器的时钟频率CK_CNT等于ck_psc/psc+1
//系统时钟ck_psc:64M
void TIM1_Init(u16 arr,u16 psc)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = arr;
TIM_TimeBaseStructure.TIM_Prescaler = psc;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = arr/2;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
}
#define ADC1_DR_Address ((uint32_t)0x4001244C)
u16 ADCRegularVal[NPT+15];
//初始化DMA
void DMA1_Init(void)
{
DMA_InitTypeDef DMA_InitStructure;
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
DMA_DeInit(DMA1_Channel1);
DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)ADCRegularVal;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = NPT;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel1, &DMA_InitStructure);
DMA_Cmd(DMA1_Channel1, ENABLE); //使能DMA
}
//等待DMA1传输结束，这个时候就可以读取ADC的值了
void Wait_ADC1_DMA1TransportOver(void){
while(!DMA_GetFlagStatus(DMA1_FLAG_TC1)); //等待DMA传输完成
DMA_ClearFlag(DMA1_FLAG_TC1); //清除传输完成标志
}
//初始化ADC
//定时器周期触发
void Adc_Init(void)
{
ADC_InitTypeDef ADC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA |RCC_APB2Periph_ADC1 , ENABLE ); //使能ADC1通道时钟
RCC_ADCCLKConfig(RCC_PCLK2_Div4); //设置ADC分频因子4 64M/4=16M
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; //PA8PWM输出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
//PA0 作为模拟通道输入引脚
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN; //模拟输入引脚
GPIO_Init(GPIOA, &GPIO_InitStructure);
TIM1_Init(25,63); //40K的采样率
DMA1_Init(); //初始化DMA
ADC_DeInit(ADC1); //复位ADC1,将外设 ADC1 的全部寄存器重设为缺省值
ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
ADC_InitStructure.ADC_ScanConvMode = DISABLE;
ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfChannel = 1;
ADC_Init(ADC1, &ADC_InitStructure);
/* ADC1 regular channel0 configuration */
ADC_RegularChannelConfig(ADC1, ADC_Channel_0, 1, ADC_SampleTime_13Cycles5); //设置规则通道ADC的采样率 28.5个周期
ADC_DMACmd(ADC1, ENABLE); //使能ADC DMA
ADC_ExternalTrigConvCmd(ADC1, ENABLE); //ADC外部触发使能
ADC_Cmd(ADC1, ENABLE); //使能指定的ADC1
ADC_ResetCalibration(ADC1); //使能复位校准
while(ADC_GetResetCalibrationStatus(ADC1)); //等待复位校准结束
ADC_StartCalibration(ADC1); //开启AD校准
while(ADC_GetCalibrationStatus(ADC1)); //等待校准结束
TIM_Cmd(TIM1, ENABLE); //使能TIM1定时器
TIM_CtrlPWMOutputs(TIM1, ENABLE); //CH1 PWM输出使能
}
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