Multi Channel ADC reading.

[to_sam_kim]

Posted on September 14, 2013 at 02:04

Hello,

I tried to read two analog inputs from PA3(ADC1_IN3) and PA5(ADC1_IN5). I expected tmpADC[0] has the input data of PA3 and tmpADC[1] has the input data of PA5. However, both tmpADC[0] and tmpADC[1] always have the input data of PA3.  I read reference manual multiple times, but I couldn't figure out what is wrong. Please let me know what is problem. I attached my code below(only ADC part). Thanks  &sharpinclude <stm32f4xx.h> void ADC_Init(void) {  GPIOA->MODER   |= (3UL<<6)|(3UL<<10);     /*Set PA3 as an analog input, ADC1_IN3, Set PA5 as an analog input ADC1_IN5*/  GPIOA->PUPDR   &= ~((3UL<<6)|(3UL<<10));   /*No Pull up and down resistor*/    RCC->APB2ENR   =(1<<8);       /*ADC1 clk enable*/  ADC1->CR1 = 0;  ADC1->CR2 = (1UL<<0)|          /*ADC1 power on */             (1UL<<1);          /*Continuous conversion*/                        ADC1->SMPR1 = 0;  ADC1->SMPR2 = 0;  ADC1->SQR1 = (1<<20);                   /* sequence length: two regular conversions*/  ADC1->SQR2 = 0;  ADC1->SQR3 = (3UL<<0)|(5UL<<5);         /*1st conversion = ADC1_lN3, 2nd conversion = ADC1_IN5*/  ADC->CCR = (1UL<<16);          /*fpclk2/4 = 21Mhz */ }   short unsigned int get_ADC(void) { ADC1->CR2 |= (1<<30);  while(!(ADC1->SR & 0x2));  return ADC1->DR; } int main (void) {        tmpADC[0]  = get_ADC();    // expecting have data from ADC1_IN3           tmpADC[1] = get_ADC();   //expecting have data from ADC1_IN5 } #stm32f4 #discovery-board #adc-dma

[Tesla DeLorean]

Posted on October 08, 2013 at 22:35

I've built a 5x version in Keil that seems serviceable, and produces values in the 0-4095 range, not sure what's going on here.

[csfarnham]

Posted on October 09, 2013 at 07:41

Well I tried the code in a new project and it worked flawlessly even though the code running was identical.  Very strange.  Thank you for your help.

Chris

[djackson]

Posted on April 17, 2014 at 23:20

What's the cut-off for ''slow speed''?

[Tesla DeLorean]

Posted on April 17, 2014 at 23:32

What's the cut-off for ''slow speed''?

SampleTime+12 vs your ability to service the EOC interrupt. I haven't plotted the curve, DMA requires no thought. The total conversion time is calculated as follows: Tconv = Sampling time + 12 cycles Example: With ADCCLK = 30 MHz and sampling time = 3 cycles: Tconv = 3 + 12 = 15 cycles = 0.5 μs with APB2 at 60 MHz

[gavinli]

Posted on January 12, 2015 at 17:46

Clive1

I used your first posted program with a little modification to convert the same channel for 8 times, but I find only the first 4 conversions are ''correct'' and the second 4 conversions are ''wrong''. What is wrong in the program? Please help. the converted values are: 0x819, 0x817, 0x818, 0x818, 0x6F8, 0x638, 0x517, 0x464 The values get smaller and smaller.

typedef struct { 
int chn_nr; //total channels 
uint8 chn[TOTAL_CHN]; 
} ADCDev; 
//const ADCDev adc1 = {8, { 4, 4, 4, 4, 4, 4, 4, 4 } }; 
const ADCDev adc1 = {8, {16, 16, 16, 16, 16, 16, 16, 16} }; 
void ADC_Configuration(uint16_t *ADCConvertedValues) 
{ 
ADC_InitTypeDef ADC_InitStructure; 
ADC_CommonInitTypeDef ADC_CommonInitStructure; 
DMA_InitTypeDef DMA_InitStructure; 
/* Enable peripheral clocks *************************************************/ 
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE); 
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE); 
/* DMA2_Stream0 channel0 configuration **************************************/ 
DMA_DeInit(DMA2_Stream0); 
DMA_InitStructure.DMA_Channel = DMA_Channel_0; 
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR; 
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)ADCConvertedValues; 
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory; 
DMA_InitStructure.DMA_BufferSize = ADC1; 
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_FIFOMode = DMA_FIFOMode_Disable; /// 
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull; 
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; 
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; 
DMA_Init(DMA2_Stream0, &DMA_InitStructure); 
/* DMA2_Stream0 enable */ 
DMA_Cmd(DMA2_Stream0, ENABLE); 
/* ADC Common Init **********************************************************/ 
ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent; 
ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2; 
ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled; 
ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles; 
ADC_CommonInit(&ADC_CommonInitStructure); 
ADC_TempSensorVrefintCmd(ENABLE); 
/* ADC1 Init ****************************************************************/ 
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b; 
ADC_InitStructure.ADC_ScanConvMode = ENABLE; 
ADC_InitStructure.ADC_ContinuousConvMode = ENABLE; 
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None; 
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1; 
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right; 
ADC_InitStructure.ADC_NbrOfConversion = adc1.chn_nr; 
ADC_Init(ADC1, &ADC_InitStructure); 
/* ADC1 regular channel configuration ******************************/ 
//ADC_RegularChannelConfig(ADC1, ADC_Channel_3, 1, ADC_SampleTime_480Cycles); // PA3 
//ADC_RegularChannelConfig(ADC1, ADC_Channel_5, 2, ADC_SampleTime_480Cycles); // PA5 
for (int i=0;i<sizeof(adc1.chn_nr);i++) 
ADC_RegularChannelConfig(ADC1, adc1.chn[i], i+1, ADC_SampleTime_3Cycles); 
/* Enable DMA request after last transfer (Single-ADC mode) */ 
ADC_DMARequestAfterLastTransferCmd(ADC1, ENABLE); 
/* Enable ADC1 DMA */ 
ADC_DMACmd(ADC1, ENABLE); 
/* Enable ADC1 **************************************************************/ 
ADC_Cmd(ADC1, ENABLE); 
/* Start ADC1 Software Conversion */ 
ADC_SoftwareStartConv(ADC1); 
} 

[Tesla DeLorean]

Posted on January 12, 2015 at 19:09

DMA_InitStructure.DMA_BufferSize = ADC1;

//????

[gavinli]

Posted on January 12, 2015 at 21:07 Hi Clive1 Sorry, I made a mistake when I clean up the code for this post. it is adc1.chn_nr; The question is still the same, why one the first 4 conversions are OK? I even tried to convert 16 times, but it is only the first 4 are reasonable, and the values are getting smaller and smaller after 4 conversion.

[Tesla DeLorean]

Posted on January 12, 2015 at 21:17

The question is still the same, why one the first 4 conversions are OK? I even tried to convert 16 times, but it is only the first 4 are reasonable, and the values are getting smaller and smaller after 4 conversion.

I guess you'd have to ponder the ability of the signal source to supply current to charge the capacitor in the sample circuit, and the sample time?