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STM32F0 DMA ADC, Channels Offset

Question asked by oweno on Jul 31, 2016
Hello.  When I configure the ADC and DMA to read 5 channels,  something funny happens.   Randomly when the board is powered up (maybe 20% of the time) the channels are offset in data array.  So in the data array location 0 holds the second ADC channel in sequence instead of the first. 

Below is the init code.   I have a feeling this might be because I init the ADC before the DMA,  so sometimes the ADC completes first conversion before DMA is ready?   I will experiment, but wondering if I'm missing something else...

static void ADC_Config(void) {
    ADC_InitTypeDef ADC_InitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_StructInit(&GPIO_InitStructure);
    /* ADC1 DeInit */
    ADC_DeInit(ADC1);
 
    /* GPIOC Periph clock enable */
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);
 
    /* ADC1 Periph clock enable */
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
 
    /* Configure  as analog input */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOC, &GPIO_InitStructure);
 
    /* Configure as analog input */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
 
    /* Configure as analog input */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
 
    /* Initialize ADC structure */
    ADC_StructInit(&ADC_InitStructure);
 
    /* Configure the ADC1 in continuous mode withe a resolution equal to 12 bits  */
    ADC_InitStructure.ADC_Resolution = ADC_Resolution_10b;
    ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
    ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_ScanDirection = ADC_ScanDirection_Backward;
    ADC_Init(ADC1, &ADC_InitStructure);
 
    /* Convert the ADC1 Channel11 and channel10 with 55.5 Cycles as sampling time */
    ADC_ChannelConfig(ADC1, ADC_Channel_14, ADC_SampleTime_55_5Cycles);
    ADC_ChannelConfig(ADC1, ADC_Channel_15, ADC_SampleTime_55_5Cycles);
    ADC_ChannelConfig(ADC1, ADC_Channel_4, ADC_SampleTime_55_5Cycles);
    ADC_ChannelConfig(ADC1, ADC_Channel_8, ADC_SampleTime_55_5Cycles);
    ADC_ChannelConfig(ADC1, ADC_Channel_9, ADC_SampleTime_55_5Cycles);
    ADC_ChannelConfig(ADC1, ADC_Channel_1, ADC_SampleTime_55_5Cycles);
 
    /* ADC Calibration */
    ADC_GetCalibrationFactor(ADC1);
 
    /* ADC DMA request in circular mode */
    ADC_DMARequestModeConfig(ADC1, ADC_DMAMode_Circular);
 
    /* Enable ADC_DMA */
    ADC_DMACmd(ADC1, ENABLE);
 
    /* Enable the ADC peripheral */
    ADC_Cmd(ADC1, ENABLE);
 
    /* Wait the ADRDY flag */
    while (!ADC_GetFlagStatus(ADC1, ADC_FLAG_ADRDY))
        ;
 
    /* ADC1 regular Software Start Conv */
    ADC_StartOfConversion(ADC1);
}
 
 
static void DMA_Config(void) {
    DMA_InitTypeDef DMA_InitStructure;
    /* DMA1 clock enable */
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
 
    /* DMA1 Channel1 Config */
    DMA_DeInit(DMA1_Channel1);
    DMA_StructInit(&DMA_InitStructure);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t) ADC1_DR_Address;
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t) RegularConvData_Tab;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = 6;
    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);
 
    /* DMA1 Channel1 enable */
    DMA_Cmd(DMA1_Channel1, ENABLE);
 
}

  Then in calling them in this order:

/* ADC1 configuration */
ADC_Config();
 
/* DMA configuration */
DMA_Config();

 And doing this to read results:

if ((DMA_GetFlagStatus(DMA1_FLAG_TC1)) == SET) {
    DMA_ClearFlag(DMA1_FLAG_TC1);
 
    knobValues[4] = RegularConvData_Tab[0];
    knobValues[0] = RegularConvData_Tab[1];
    knobValues[1] = RegularConvData_Tab[2];
    knobValues[3] = RegularConvData_Tab[3];
    knobValues[2] = RegularConvData_Tab[4];
    knobValues[5] = RegularConvData_Tab[5];
}

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