在工作中接到一個任務需要使用定時器輸出不同的波形,在網上查閱了資料後發現可以使用DMA給定時器的捕獲比較寄存器地址傳輸數據來控制輸出PWM。
話不多說先貼代碼
void TIM3_GPIO_INIT(){
GPIO_InitTypeDef GPIO_InitStructure;
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE );
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
GPIO_Init( GPIOA, &GPIO_InitStructure );
GPIO_PinAFConfig( GPIOA, GPIO_PinSource6, GPIO_AF_1 );
}
void TIM3_INIT(void){
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
RCC_APB1PeriphClockCmd( RCC_APB1Periph_TIM3, ENABLE );
TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInitStructure.TIM_Prescaler = 48 - 1; //產生800K HZ脈衝
// TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInitStructure.TIM_Period =1599;
TIM_TimeBaseInit( TIM3, &TIM_TimeBaseInitStructure );
TIM_OCInitStructure.TIM_Pulse = 0;
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init( TIM3, &TIM_OCInitStructure );
/* TIM Interrupts enable */
TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);
TIM_Cmd( TIM3, ENABLE );
}
void LCD_DMA_INIT(void){
DMA_InitTypeDef DMA_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
DMA_DeInit( DMA1_Channel3 );
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&TIM3->CCR1); //外設地址
DMA_InitStructure.DMA_MemoryBaseAddr = ( uint32_t )ucTM1804EncodeBuffer; //自定義數組地址
DMA_InitStructure.DMA_BufferSize = TM1804_BUFFER_SIZE; //數據長度
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST; //數據傳輸方向爲外設
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外設地址寄存器自動增加禁止
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //內存地址自增
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord; //外設的數據大小,因爲TIM8->CCR1爲16位寄存器
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord; //內存數據大小爲uint16_t
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular; //DMA循環傳輸模式
DMA_InitStructure.DMA_Priority = DMA_Priority_High; //優先級爲高
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_ITConfig(DMA1_Channel3,DMA_IT_TC,ENABLE);
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Ch2_3_DMA2_Ch1_2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_InitStructure.NVIC_IRQChannelPriority = 1;
NVIC_Init(&NVIC_InitStructure);
DMA_Init( DMA1_Channel3, &DMA_InitStructure );
DMA_ClearITPendingBit(DMA1_IT_TC3);
// DMA_Cmd( DMA1_Channel4, ENABLE );
TIM_DMACmd( TIM3, TIM_DMA_Update, ENABLE );
DMA_SetCurrDataCounter(DMA1_Channel3,TM1804_BUFFER_SIZE);//DMA通道的DMA緩存的大小
DMA_Cmd(DMA1_Channel3, ENABLE); //使能USART1 TX DMA1 所指示的通道
}
void DMA1_Ch2_3_DMA2_Ch1_2_IRQHandler(void){
if(DMA_GetITStatus(DMA1_IT_TC3) !=RESET){
TIM_SetCompare1(TIM3,0);
DMA_Cmd(DMA1_Channel3, DISABLE);
DMA_ClearITPendingBit(DMA1_IT_TC3);
}
}
在寫的過程中遇見了很多問題,第一次寫的時候一直不能進行數據的傳輸,初始化的DMA通道是CCR對應的DMA通道,寫了DMA傳輸中斷DEBUG也不能進入中斷,這裏有個函數可以使能或者失能指定的TIMx的DMA請求:
void TIM_DMACmd(TIM_TypeDef* TIMx, u16 TIM_DMASource, FunctionalState Newstate)
其中TIM_DMASource
輸入參數TIM_DMASource使能或者失能TIM的中斷。最開始我選擇的是TIM_DMA_CC3
TIM捕獲/比較3DMA源,但一直不能輸出我想要的波形,之後向別人請教之後發現需要選擇
TIM_DMA_Update ,TIM更新DMA源,這個,這個中斷源的意思是當計數值從0計數到arr後觸發一次中斷,產生一次DMA傳輸,可以實現一個完整的週期之後改變脈衝值,但如果使用的TIM_DMA_CC3這個的時候,當從0計數到脈衝值的時候就產生了一次中斷,改變了脈衝值,循環往復,不能產生一個完整的週期,而我要實現的功能對應於定時器計數到arr之後觸發DMA傳輸數據來改變定時器對應通道的捕獲比較寄存器的值從而輸出我想要的波形。