DMA only fetching 2 values from ADC

[John Hite]

Posted on April 20, 2017 at 18:01

STM32F437

This is an update from my previous thread:

https://community.st.com/message/154808-stm32f4-adcdma-always-returns-same-value

 

The ADC2 DR has the right value in it but the DMA is not working as I thought it would. It is only transferring 2 values although the array size and # of readings is 8. Condensed code is below.

Thanks,

JH

#define ADC_NUM_READINGS 8  //  Changing these will require a significant change

void AdcInit(void);

uint16_t readVoltage(void);static uint16_t adc2_result[ADC_NUM_READINGS];

static const DMA_InitTypeDef dma2 =

{    DMA_Channel_1,    ADC2_BASE + 0x4C,                       //  ADC2->DR    (uint32_t)&adc2_result,               //Mememory 0 base address    DMA_DIR_PeripheralToMemory,    ADC_NUM_READINGS,    DMA_PeripheralInc_Disable,    DMA_MemoryInc_Enable,    DMA_PeripheralDataSize_HalfWord,    DMA_MemoryDataSize_HalfWord,    DMA_Mode_Circular,    DMA_Priority_High,    DMA_FIFOMode_Disable,    DMA_FIFOThreshold_Full,    DMA_MemoryBurst_Single,    DMA_PeripheralBurst_Single};

void adcInit(void)

{    ADC_CommonInitTypeDef cInit;    ADC_InitTypeDef init;    OS_ERR err;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC2, ENABLE);

    DMA_DeInit(DMA2_Stream2);

    DMA_Init(DMA2_Stream2, (DMA_InitTypeDef*)&dma2);    DMA_Cmd(DMA2_Stream2, ENABLE);

    cInit.ADC_Mode = ADC_Mode_Independent;

    cInit.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;    cInit.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;    cInit.ADC_Prescaler = ADC_Prescaler_Div2;    ADC_CommonInit(&cInit);

    init.ADC_Resolution = ADC_Resolution_12b;

    init.ADC_ScanConvMode = DISABLE;    init.ADC_ContinuousConvMode = ENABLE;    init.ADC_DataAlign = ADC_DataAlign_Right;    init.ADC_NbrOfConversion = 1;    ADC_Init(ADC2, &init);

    ADC_RegularChannelConfig(ADC2, ADC_Channel_6, 1, ADC_SampleTime_15Cycles);

    //ADC_DMARequestAfterLastTransferCmd(ADC2, ENABLE);    ADC_DMACmd(ADC2, ENABLE);    ADC_Cmd(ADC2, ENABLE);    ADC_SoftwareStartConv(ADC2);}

uint16_t readVoltage(void)

{

   return adc2_result[0];   // I set a break point here and examine the array. Locations 2-7 are always zero.

}

[Tesla DeLorean]

Posted on April 20, 2017 at 18:56

ADC_InitTypeDef init = { 0 }; // try doing this

Also

ADC2_BASE + 0x4C,                       //  ADC2->DR

Wouldn't (uint32_t)&ADC2->DR be simpler/clearer?

[S.Ma]

Posted on April 20, 2017 at 21:11 The original post was too long to process during our migration. Please click on the provided URL to read the original post. https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I6rz&d=%2Fa%2F0X0000000bwy%2FmHDLRRpZscAToHdpPUWEEb2pUH3oSHKoFDNQQfdVvFY&asPdf=false

[John Hite]

Posted on April 21, 2017 at 16:39

Thanks for the post Clive. I walked through your code and the only difference I see is in the buffer size and that you define external trigger configurations. But since I am using continuous ADC triggering that shouldn't matter.

The fact remains that if I enable DMA the ADC never updates its data register after the first reading. Also I still only get one or two values from the DMA for that first transfer. I am beginning to wonder if the DMA does not work without an ISR manipulating its registers.

JH

[S.Ma]

Posted on April 21, 2017 at 18:33

Actually with the external trigger, the ADC buffer fills up even if the code is stopped by breakpoint. No interrupt, full HW...

[John Hite]

Posted on April 21, 2017 at 18:59

Could you expand on 'No interrupt, full HW...' a bit?

 I am trying to figure out why the DMA is shutting down my ADC.

Thanks,

JH

[Tesla DeLorean]

Posted on April 21, 2017 at 23:40

DMA in the background, happens behind back of CPU and debugger

&sharpdefine ADC_NUM_READINGS 8 // Changing these will require a significant change

void adcInit(void);uint16_t readVoltage(void);volatile uint16_t adc2_result[ADC_NUM_READINGS]; static DMA_InitTypeDef dma2 ={ DMA_Channel_1, (uint32_t)&ADC2->DR, // ADC2->DR (uint32_t)&adc2_result[0], // Memory 0 base address DMA_DIR_PeripheralToMemory, ADC_NUM_READINGS, DMA_PeripheralInc_Disable, DMA_MemoryInc_Enable, DMA_PeripheralDataSize_HalfWord, DMA_MemoryDataSize_HalfWord, DMA_Mode_Circular, DMA_Priority_High, DMA_FIFOMode_Disable, DMA_FIFOThreshold_Full, DMA_MemoryBurst_Single, DMA_PeripheralBurst_Single};

void GPIO_Configure(void)

{ GPIO_InitTypeDef GPIO_InitStructure;

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; GPIO_Init(GPIOC, &GPIO_InitStructure);}

void adcInit(void)

{ ADC_CommonInitTypeDef cInit; ADC_InitTypeDef init = { 0 }; // Or initialize ALL fields DMA_DeInit(DMA2_Stream2); DMA_Init(DMA2_Stream2, (DMA_InitTypeDef*)&dma2); DMA_Cmd(DMA2_Stream2, ENABLE);

cInit.ADC_Mode = ADC_Mode_Independent;

cInit.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles; cInit.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled; cInit.ADC_Prescaler = ADC_Prescaler_Div2; ADC_CommonInit(&cInit); init.ADC_Resolution = ADC_Resolution_12b; init.ADC_ScanConvMode = DISABLE; init.ADC_ContinuousConvMode = ENABLE; init.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None; init.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1; init.ADC_DataAlign = ADC_DataAlign_Right; init.ADC_NbrOfConversion = 1; ADC_Init(ADC2, &init); ADC_RegularChannelConfig(ADC2, ADC_Channel_12, 1, ADC_SampleTime_15Cycles);

ADC_DMARequestAfterLastTransferCmd(ADC2, ENABLE); // Recycles after DMA completes

ADC_DMACmd(ADC2, ENABLE);

ADC_Cmd(ADC2, ENABLE);

ADC_SoftwareStartConv(ADC2); // Start first time} uint16_t readVoltage(void){ return adc2_result[0]; // I set a break point here and examine the array. Locations 2-7 are always zero.}

/**

* @brief Main program * @param None * @retval None */int main(void){ /*!< At this stage the microcontroller clock setting is already configured, this is done through SystemInit() function which is called from startup file (startup_stm32f4xx.s) before to branch to application main. To reconfigure the default setting of SystemInit() function, refer to system_stm32f4xx.c file */

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2 | RCC_AHB1Periph_GPIOC, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC2, ENABLE); GPIO_Configure(); memset((void *)adc2_result, 0xCD, sizeof(adc2_result)); adcInit(); while(1) { static int i = 0; i += readVoltage(); } while (1) { }}

[waclawek.jan]

Posted on April 23, 2017 at 11:03

 I am trying to figure out why the DMA is shutting down my ADC.

And does it? How do you know? Post the content of relevant ADC and DMA registers.

JW

[Tesla DeLorean]

Posted on April 23, 2017 at 16:02

There are problem with the ADC initialization due to several missing fields containing junk values. The ADC_DMARequestAfterLastTransferCmd(ADC2, ENABLE); is needed to sustain the stream.

Keil also threw warnings about the addresses in the constant structure, but the linker seemed to fix up properly.