有没有人知道，STM32 DAC 在DMA模式下启动的每次时间是否固定？

dtszcr · 发表于 2012-11-30 10:06:51

我最近用STM32F103VCT6 的DAC产生两路同频正弦波，通过定时器1延时控制两个波形的相位。但是不知道为什么调节的时候，相位间隔并不是以定时器的分辨率步进，要调节好几个值相位才能动一下，而且相位变动值都不固定。
程序是每次步进一下，重新设置DMA 和DAC ，然后先打开第一路DAC的时钟TIMx1，然后打开定时器，定时中断到就打开第二路的时钟TIMx2，不知道是不是我的程序问题，还是STM32本身启动DMA DAC时间就不确定。
可以确定定时器是没问题，我用IO口翻转做个实验，可以实现很精确的步进。
DMA 和DAC 配置程序如下
NVIC_SETFAULTMASK(); //关闭总中断
SysTick_ITConfig(DISABLE);
TIM_Cmd(TIM2, DISABLE); /* TIM2 enable counter */
TIM_Cmd(TIM4, DISABLE); /* TIM4 enable counter */

DMA_Cmd(DMA2_Channel3, DISABLE); /* Enable DMA1 Channel3 */
DAC_Cmd(DAC_Channel_1, DISABLE); /* Enable DAC Channel1 */
DAC_DMACmd(DAC_Channel_1,DISABLE); /* Enable DMA for DAC Channel1 */

DMA_Cmd(DMA2_Channel4, DISABLE); /* Enable DMA2 Channel3 */
DAC_Cmd(DAC_Channel_2, DISABLE); /* Enable DAC Channel2 */
DAC_DMACmd(DAC_Channel_2, DISABLE); /* Enable DMA for DAC Channel2 */
TIM_DeInit(TIM2); /* Resets the TIM2 */
TIM_DeInit(TIM4); /* Resets the TIM4 */

TIM_PrescalerConfig(TIM2, 0x00, TIM_PSCReloadMode_Update); /* TIM2 Configuration */
TIM_SetAutoreload(TIM2, T); //设置定时器2自动重装
TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update); /* TIM2 TRGO selection */

/* DAC channel1 Configuration */
DAC_InitStructure.DAC_Trigger = DAC_Trigger_T2_TRGO;
DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Disable;
DAC_Init(DAC_Channel_1, &DAC_InitStructure);

/* DMA2 channel3 configuration */
DMA_DeInit(DMA2_Channel3);
DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR8R1_Address;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)&Escalator8bit1;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = 256;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA2_Channel3, &DMA_InitStructure);

DMA_Cmd(DMA2_Channel3, ENABLE); /* Enable DMA1 Channel3 */
DAC_Cmd(DAC_Channel_1, ENABLE); /* Enable DAC Channel1 */
DAC_DMACmd(DAC_Channel_1, ENABLE); /* Enable DMA for DAC Channel1 */
//TIM_Cmd(TIM2, ENABLE); /* TIM2 enable counter */

TIM_PrescalerConfig(TIM4, 0x00, TIM_PSCReloadMode_Update); /* TIM4 Configuration */
TIM_SetAutoreload(TIM4, T); //设置定时器4自动重装
TIM_SelectOutputTrigger(TIM4, TIM_TRGOSource_Update); /* TIM4 TRGO selection */

/* DAC channel2 Configuration*/
DAC_InitStructure.DAC_Trigger = DAC_Trigger_T4_TRGO;
DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Disable;
DAC_Init(DAC_Channel_2, &DAC_InitStructure);

/* DMA2 channel4 configuration */
DMA_DeInit(DMA2_Channel4);
DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR8R2_Address;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)&Escalator8bit2;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = 256;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA2_Channel4, &DMA_InitStructure);

DMA_Cmd(DMA2_Channel4, ENABLE); /* Enable DMA2 Channel3 */
DAC_Cmd(DAC_Channel_2, ENABLE); /* Enable DAC Channel2 */
DAC_DMACmd(DAC_Channel_2, ENABLE); /* Enable DMA for DAC Channel2 */


TIM_Cmd(TIM2, ENABLE); /* TIM2 enable counter */ // 此次打开第一路DAC
NVIC_RESETFAULTMASK();//开放总中断
Time1_Configuration(); //配置定时器1，用来延时产生第二路DAC，在定时器1中断中打开第二路DAC

定时器1中断中启动第二路DAC的程序如下
void TIM1_UP_IRQHandler(void)
{
TIM_ClearITPendingBit(TIM1, TIM_IT_Update);
TIM_ITConfig(TIM1, TIM_IT_Update, DISABLE );
TIM_Cmd(TIM1, DISABLE);
TIM_Cmd(TIM4, ENABLE); /* TIM4 enable counter */ //此处打开第二路DAC
SysTick_ITConfig(ENABLE);
}