STM32學(xué)習(xí)記錄19 定時器觸發(fā)ADC

int main(void)

{

#ifdef DEBUG

debug();

#endif

/* System clocks configuration ---------------------------------------------*/

RCC_Configuration();

/* NVIC configuration ------------------------------------------------------*/

NVIC_Configuration();

/* GPIO configuration ------------------------------------------------------*/

GPIO_Configuration();

/* TIM1 configuration ------------------------------------------------------*/

/* Time Base configuration */

TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);

TIM_TimeBaseStructure.TIM_Period = 0xFF;

TIM_TimeBaseStructure.TIM_Prescaler = 0x4;

TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

/* TIM1 channel1 configuration in PWM mode */

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse = 0x7F;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;

TIM_OC1Init(TIM1, &TIM_OCInitStructure);

/* DMA1 Channel1 Configuration ----------------------------------------------*/

DMA_DeInit(DMA1_Channel1);

DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;

DMA_InitStructure.DMA_MemoryBaseAddr = (u32)ADC_RegularConvertedValueTab;

DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;

DMA_InitStructure.DMA_BufferSize = 32;

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_Normal;

DMA_InitStructure.DMA_Priority = DMA_Priority_High;

DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

DMA_Init(DMA1_Channel1, &DMA_InitStructure);

/* Enable DMA1 channel1 */

DMA_Cmd(DMA1_Channel1, ENABLE);

/* ADC1 configuration ------------------------------------------------------*/

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 channel14 configuration */

ADC_RegularChannelConfig(ADC1, ADC_Channel_14, 1, ADC_SampleTime_13Cycles5);

/* Set injected sequencer length */

ADC_InjectedSequencerLengthConfig(ADC1, 1);

/* ADC1 injected channel Configuration */

ADC_InjectedChannelConfig(ADC1, ADC_Channel_11, 1, ADC_SampleTime_71Cycles5);

/* ADC1 injected external trigger configuration */

ADC_ExternalTrigInjectedConvConfig(ADC1, ADC_ExternalTrigInjecConv_None);

/* Enable automatic injected conversion start after regular one */

ADC_AutoInjectedConvCmd(ADC1, ENABLE);

/* Enable ADC1 DMA */

ADC_DMACmd(ADC1, ENABLE);

/* Enable ADC1 external trigger */

ADC_ExternalTrigConvCmd(ADC1, ENABLE);

/* Enable JEOC interupt */

ADC_ITConfig(ADC1, ADC_IT_JEOC, ENABLE);

/* Enable ADC1 */

ADC_Cmd(ADC1, ENABLE);

/* Enable ADC1 reset calibaration register */

ADC_ResetCalibration(ADC1);

/* Check the end of ADC1 reset calibration register */

while(ADC_GetResetCalibrationStatus(ADC1));

/* Start ADC1 calibaration */

ADC_StartCalibration(ADC1);

/* Check the end of ADC1 calibration */

while(ADC_GetCalibrationStatus(ADC1));

/* TIM1 counter enable */

TIM_Cmd(TIM1, ENABLE);

/* TIM1 main Output Enable */

TIM_CtrlPWMOutputs(TIM1, ENABLE);

/* Test on channel1 transfer complete flag */

while(!DMA_GetFlagStatus(DMA1_FLAG_TC1));

/* Clear channel1 transfer complete flag */

DMA_ClearFlag(DMA1_FLAG_TC1);

/* TIM1 counter disable */

TIM_Cmd(TIM1, DISABLE);

while (1)

{

}

}

2：關(guān)于AD的DMA暫時不介紹，主要介紹定時器和ADC的關(guān)聯(lián)，下面是例程中兩者的關(guān)鍵函數(shù)

那么如何得到上升沿呢？需要看一下定時器的內(nèi)容

2.2定時器中有這么一段話：輸出部分產(chǎn)生一個中間波形OCxRef(高有效)作為基準(zhǔn)，鏈的末端決定最終輸出信號的極性。 也就是說OCxREF只是一個中間信號，我們關(guān)心的是最終的信號。

那么最后一句話中最終信號的極性如何確定呢？繼續(xù)往下看：

從圖中可以看到中中間參看信號OC1REF經(jīng)過TIM1_CCER_CCIE TIM1_CCER_CCIP最終決定OC1的輸出極性?？匆幌聰?shù)據(jù)手冊，輸出模式中貌似只有PWM模式可以滿足2.1中提到的，可以產(chǎn)生一個上升沿來觸發(fā)AD轉(zhuǎn)換。

現(xiàn)在可以解釋代碼了，結(jié)合官網(wǎng)的源文件和寄存器來說明一下會更加的深刻吧！

3 代碼解釋

3.1 定時器設(shè)定為PWM模式

①頭文件中

②頭文件中定義

③頭文件中定義

#define

TIM_OCPolarity_Low((uint16_t)0x0002)賦值給TIMx->CCER，對照文檔看出

OC1是低電平有效，這一點非常重要，說明在最后的輸出端口是低電平有效的，

TIMx_ARR：自動裝載寄存器， 確定PWM的頻率，

TIM_CCRx：捕獲/比較寄存器，確定只占空比

TIMx_CNT：計數(shù)器寄存器。

也就是說當(dāng)CNT

3.2 定時器和PWM打開

上面代碼相對簡單，就是打開定時器，使能PWM輸出。需要注意的是一定要有TIM_CtrlPWMOutputs(TIM1, ENABLE);函數(shù)的調(diào)用。其中就是使能了TIMx_BDTR_MOE。