STM32 MCU ADC rule group multi-channel conversion DMA mode

       A / D converter （Analog To Digital Converter） abbreviation ADC（ Or you could write it as A/D）, It refers to a device that converts a continuously changing analog signal into a discrete digital signal .

       Direct memory access technology （Direct Memory Access） abbreviation DMA.DMA Used to provide high-speed data transfer between peripheral and memory or between memory and memory . need not CPU intervention , Data can be obtained by DMA Moving fast , This saves money CPU Your resources can do other operations .DMA The essence of transmission is address to address operation , You can put DMA Understood as a CPU Of “ secretary ”.

       ADC The reference voltage is ADC An important indicator of .STM32 The chip is just 100 And above pin models have external reference voltage pin VREF+ and VREF-;64 And less than 64 Foot model , The reference voltage pin is connected to by default inside the chip ADC The power supply pin VDDA and VSSA.

       because ADC Rule group multi-channel conversion , Only the data of the last channel can be read , therefore ADC Multi channel conversion for DMA Pattern , When each access conversion is completed , send out DMA request , adopt DMA Directly transfer to the set memory buffer , So it solved ADC The problem of multi-channel conversion data being covered , meanwhile CPU No need to read frequently ADC The data of , Greatly improve execution efficiency .

       By looking up STM32F1 Reference manual for , We can know ADC1 Of DMA Transport channel mapped to DMA1 Of Channel1.ADC1 May by TIM3_TRGO Event triggered transformation . This passage TIM3 The update event of triggers ADC Rule group 4 Channel conversion . In actual projects , We use this 4 road ADC Read the output voltage of the four Hall angle sensors and then calculate the angle of the manipulator , Use external trigger ADC Rule group conversion can avoid ADC Waste of resources caused by circular conversion mode . Next on the code .

void Timer_Init(void)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
	
    TIM_TimeBaseStructure.TIM_Period=1000-1;
    TIM_TimeBaseStructure.TIM_Prescaler=72-1;
    TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);
	
    TIM_Cmd(TIM3, ENABLE);
    TIM_SelectOutputTrigger(TIM3,TIM_TRGOSource_Update);// Set update event as trigger output 
}

void ADC_DMA_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    ADC_InitTypeDef ADC_InitStructure;
    DMA_InitTypeDef DMA_InitStructure;
    
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1,ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOB,ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1,ENABLE);
    RCC_ADCCLKConfig(RCC_PCLK2_Div6);//72M/6=12M
    //init GPIO
    GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AIN;
    GPIO_InitStructure.GPIO_Pin=GPIO_Pin_6|GPIO_Pin_7;
    GPIO_Init(GPIOA,&GPIO_InitStructure);
    GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AIN;
    GPIO_InitStructure.GPIO_Pin=GPIO_Pin_0|GPIO_Pin_1;
    GPIO_Init(GPIOB,&GPIO_InitStructure);
    //init DMA
    DMA_DeInit(DMA1_Channel1);
    DMA_InitStructure.DMA_PeripheralBaseAddr=(unsigned int)&(ADC1->DR);
    DMA_InitStructure.DMA_MemoryBaseAddr=(unsigned int)&ADCBuffer[0];
    DMA_InitStructure.DMA_DIR=DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize=4;
    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);
    //init ADC1
    ADC_DeInit(ADC1);
    ADC_InitStructure.ADC_Mode=ADC_Mode_Independent;
    ADC_InitStructure.ADC_ScanConvMode=ENABLE;
    ADC_InitStructure.ADC_ContinuousConvMode=DISABLE;
    ADC_InitStructure.ADC_ExternalTrigConv=ADC_ExternalTrigConv_T3_TRGO;// Set the external signal TIM3_TRGO set out 
    ADC_InitStructure.ADC_DataAlign=ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfChannel=4;
    ADC_Init(ADC1,&ADC_InitStructure);
    ADC_RegularChannelConfig(ADC1,ADC_Channel_6,1,ADC_SampleTime_239Cycles5);
    ADC_RegularChannelConfig(ADC1,ADC_Channel_7,2,ADC_SampleTime_239Cycles5);
    ADC_RegularChannelConfig(ADC1,ADC_Channel_8,3,ADC_SampleTime_239Cycles5);
    ADC_RegularChannelConfig(ADC1,ADC_Channel_9,4,ADC_SampleTime_239Cycles5);
    ADC_DMACmd(ADC1,ENABLE);
    ADC_Cmd(ADC1,ENABLE);
    //calibrate ADC1
    ADC_ResetCalibration(ADC1);
    while(ADC_GetResetCalibrationStatus(ADC1));
    ADC_StartCalibration(ADC1);
    while(ADC_GetCalibrationStatus(ADC1));
    //enable ADC1 external trigger
    ADC_ExternalTrigConvCmd(ADC1,ENABLE);
}

stay main Middle note initialization function in function ,TIM3、ADC、DMA After configuration ,TIM3 Will each 1ms Trigger once ADC Rule group channel conversion , The result of the conversion will be DMA Transfer to a predefined buffer ADCBuffer, Just read it in time ADCBuffer The data in can be obtained ADC Value of channel conversion . If the data is not read in time , The read data is easily overwritten , To this end, we can ADCBuffer And DMA Channel cache (DMA_BufferSize) Set as the of the measured data 2 Multiple size , When the first rule group 4 After the channels are converted in turn ,DMA Transfer the data to the first half of the buffer in turn , Simultaneous setting DMA Transmit half flag bit , You can now read the current 4 Data channel conversion . At the same time, the rule group continues to convert , When the second time 4 When the channels are converted in turn , The conversion data is stored in the second half of the buffer , Simultaneous setting DMA Transmission completion flag bit , At this time, the data of the second conversion can be read .

Code download link ：STM32F1 Series single chip microcomputer multichannel ADC-DMA Mode configuration method _ Single chip microcomputer dma-C Document resources -CSDN download