Any ideas why I get those 0 - 65500 values from adc ?

[MNapi]

I have

uint16_t array[2000];

HAL_ADC_Start_DMA(&hadc1, (uint32_t*)array, 2000);

I get values from 0 up to 65535

but when I declare

uint8_t array[2000];

I get values 0-255

I shouldn't be bigger than 4095 since it is 12 bit resolution for ADC

I have STM32L416KBU6

I do not have the problem with STM32F446RE

[Tesla DeLorean]

Depends on the 12-bit being left or right aligned, you can pick either. Left aligned would have the 12-bits in the high order bits of a 16-bit word, and thus up to 65500 ish.

[S.Ma]

How the ADC is configured? It could be the DMA is wrongly configured, could be direction or wrong ADC number. Have you also aligned the 16 bit array to a even address number? (#pragma or align keyword, compiler dependent).

[MNapi]

I tried left and right the same no change

[MNapi]

I do not see anything wrong in ADC setting I use Cube MX

static void MX_ADC1_Init(void)

{

 /* USER CODE BEGIN ADC1_Init 0 */

 /* USER CODE END ADC1_Init 0 */

 ADC_MultiModeTypeDef multimode = {0};

 ADC_ChannelConfTypeDef sConfig = {0};

 /* USER CODE BEGIN ADC1_Init 1 */

 /* USER CODE END ADC1_Init 1 */

 /**Common config

 */

 hadc1.Instance = ADC1;

 hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV2;

 hadc1.Init.Resolution = ADC_RESOLUTION_12B;

 hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;

 hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;

 hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;

 hadc1.Init.LowPowerAutoWait = DISABLE;

 hadc1.Init.ContinuousConvMode = ENABLE;

 hadc1.Init.NbrOfConversion = 1;

 hadc1.Init.DiscontinuousConvMode = DISABLE;

 hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;

 hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;

 hadc1.Init.DMAContinuousRequests = ENABLE;

 hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;

 hadc1.Init.OversamplingMode = DISABLE;

 if (HAL_ADC_Init(&hadc1) != HAL_OK)

 {

   Error_Handler();

 }

 /**Configure the ADC multi-mode

 */

 multimode.Mode = ADC_MODE_INDEPENDENT;

 if (HAL_ADCEx_MultiModeConfigChannel(&hadc1, &multimode) != HAL_OK)

 {

   Error_Handler();

 }

 /**Configure Regular Channel

 */

 sConfig.Channel = ADC_CHANNEL_5;

 sConfig.Rank = ADC_REGULAR_RANK_1;

 sConfig.SamplingTime = ADC_SAMPLETIME_12CYCLES_5;

 sConfig.SingleDiff = ADC_SINGLE_ENDED;

 sConfig.OffsetNumber = ADC_OFFSET_NONE;

 sConfig.Offset = 0;

 if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)

 {

   Error_Handler();

 }

 /* USER CODE BEGIN ADC1_Init 2 */

 /* USER CODE END ADC1_Init 2 */

}

[S.Ma]

Look at ADC + DMA examples for the closest Nucleo board and narrow down what's different.

Maybe the ADC or DMA IP is slightly different between both STM32 families and copy/paste requires code edits. This happened between STM32L496 and STM32L4R5 for DMAMUX and EXTI.

[Nix Wayne]

I think you have problem with data alignment.

Have a look at my union declaration which I use to assign to DMA call and to extract proper data when conversion is done. This is example for 3 channels.

typedef union
{
  uint32_t data[2];
	
	struct 
	{
	  uint16_t channels[4];	
	} fields;
	
} adc_buffer_s;

So my DMA call looks like:

HAL_ADC_Start_DMA(&adc.hadc1, cnv_buffer.data, 3);

where

// buffer 
adc_buffer_s cnv_buffer;

And then I get data out of buffer by accessing fields in this way:

// first channel
cnv_buffer.fields.channels[0]
 
// second channel
cnv_buffer.fields.channels[1]
 
// third channel
cnv_buffer.fields.channels[2]

A short explanation:

We have 3 channels... each channel has 16 bit data and this results in 6 bytes (3x 2bytes)... but DMA demands pointer to 32bit buffer... so we have to reserve 2x 32 bits which is enough for 4 channels. So there will be one left empty.

Why I am using union in such way? Because data will be written and aligned into memory in a such way that accesing cnv_buffer.fields.channels[X] will already give me back properly aligned data and I can avoid any additional operations to compose data when not using union.

I hope this helps.