STM32学习记录19 定时器触发ADC
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1：下面为官方例程，
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：关于AD的DMA暂时不介绍，主要介绍定时器和ADC的关联，下面是例程中两者的关键函数
/* 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);
。
。
。
。
/* Enable ADC1 */
ADC_Cmd(ADC1, ENABLE);
。
。
。
/* TIM1 counter enable */
TIM_Cmd(TIM1, ENABLE);
/* TIM1 main Output Enable */
TIM_CtrlPWMOutputs(TIM1, ENABLE);
。
。
。
/* TIM1 counter disable */
TIM_Cmd(TIM1, DISABLE);
下面分条解释，解释之前需要了解一下ADC外部触发的相关知识：
2.1首先ADC的外部触发必须是上升沿才可以启动转换。
那么如何得到上升沿呢？需要看一下定时器的内容
2.2定时器中有这么一段话：输出部分产生一个中间波形OCxRef(高有效)作为基准，链的末端决定最终输出信号的极性。 也就是说OCxREF只是一个中间信号，我们关心的是最终的信号。
那么最后一句话中最终信号的极性如何确定呢？继续往下看：
2.3末端最终信号的极性确定
从图中可以看到中中间参看信号OC1REF经过TIM1_CCER_CCIE TIM1_CCER_CCIP最终决定OC1的输出极性。看一下数据手册，输出模式中貌似只有PWM模式可以满足2.1中提到的，可以产生一个上升沿来触发AD转换。
现在可以解释代码了，结合官网的源文件和寄存器来说明一下会更加的深刻吧！
3 代码解释
3.1 定时器设定为PWM模式
/* 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);//上面的代码就不需要解释了，主要就是设置定时器的周期，需要注意的是定时器设置为向上计数模式。下面的代码逐条解释
/* TIM1 channel1 configuration in PWM mode */
①TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; //TIM1 脉冲宽度调制模式 1
| ②TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //使能输出比较状态 |
TIM_OCInitStructure.TIM_Pulse = 0x7F;
③TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //TIM1 输出比较极性低
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
①头文件中
| #define | TIM_OCMode_PWM1((uint16_t)0x0060) 赋值给TIMx->CCMR1，对比下面的文档，可以看出是设置为PWM模式1 |
②头文件中定义
| #define | TIM_OutputState_Enable((uint16_t)0x0001)赋值给TIMx->CCER寄存器 |
③头文件中定义
| #define | TIM_OCPolarity_Low((uint16_t)0x0002)赋值给TIMx->CCER，对照文档看出 |
TIMx_ARR：自动装载寄存器， 确定PWM的频率，
TIM_CCRx：捕获/比较寄存器，确定只占空比
TIMx_CNT：计数器寄存器。
也就是说当CNT
3.2 定时器和PWM打开
/* TIM1 counter enable */
TIM_Cmd(TIM1, ENABLE);
/* TIM1 main Output Enable */
TIM_CtrlPWMOutputs(TIM1, ENABLE);
。
。
。
/* TIM1 counter disable */
TIM_Cmd(TIM1, DISABLE);
上面代码相对简单，就是打开定时器，使能PWM输出。需要注意的是一定要有TIM_CtrlPWMOutputs(TIM1, ENABLE);函数的调用。其中就是使能了TIMx_BDTR_MOE。
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STM32学习记录1定时器触发AD
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