STM32F0 DMA ADC, Channels Offset

[owen]

Posted on July 31, 2016 at 15:01

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 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];
}

#stm32f0-dma-adc