STM32L476VG get max ADC sample rate

gnu · ‎2016-08-10

Posted on August 10, 2016 at 16:38

Hello everyone

I am trying to get the ADC working at max sample rate of 5.33Msps. I tested it with a 500Khz sinewave as input but I get 6 samples every period (2us) which is about

3Msps.

I set the ADC to work incontinuousmode and the DMA continuousrequest is enabled. Everything work at maximum speed( system clock set to 80Mhz). I probably missed something but I can't find what is wrong. Can anyone give me a hand or two? :) I don't know where to look at anymore, I appreciate any direction. Thank you! here the

http://www.st.com/content/ccc/resource/technical/document/reference_manual/02/35/09/0c/4f/f7/40/03/DM000835pdf/files/DM000835pdf/jcr:content/translations/en.DM000835pdf

. Everything is generated by stm32cubemx I just started DMA and ADC in main function.

/* Includes ------------------------------------------------------------------*/
#include ''stm32l4xx_hal.h''
/* USER CODE BEGIN Includes */
#include ''string.h''
/* USER CODE END Includes */
/* Private variables ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;
DMA_HandleTypeDef hdma_adc1;
TIM_HandleTypeDef htim3;
/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
void Error_Handler(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_ADC1_Init(void);
static void MX_TIM3_Init(void);
/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/
uint16_t ADC1ConvertedValues[255]; 
int c;
/* USER CODE END PFP */
/* USER CODE BEGIN 0 */

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
if (htim->Instance==TIM3){
c = c+1; // Increment C. Just for debuging
HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_2); // Toggle led every 10ms
}
}
/* USER CODE END 0 */
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration----------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* Configure the system clock */
SystemClock_Config();
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_DMA_Init();
MX_ADC1_Init();
MX_TIM3_Init();
/* USER CODE BEGIN 2 */
// -- Enables ADC DMA request 
HAL_ADC_Start_DMA(&hadc1, (uint32_t*)ADC1ConvertedValues, 255);
// -- Enables ADC and starts conversion of the regular channels. 
HAL_ADC_Start(&hadc1);
// -- Start timer 3
HAL_TIM_Base_Start_IT(&htim3);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
//HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_SET);
}
/* USER CODE END 3 */
}
/** System Clock Configuration
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct;
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_PeriphCLKInitTypeDef PeriphClkInit;
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
RCC_OscInitStruct.MSIState = RCC_MSI_ON;
RCC_OscInitStruct.MSICalibrationValue = 0;
RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
RCC_OscInitStruct.PLL.PLLM = 1;
RCC_OscInitStruct.PLL.PLLN = 40;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
Error_Handler();
}
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC;
PeriphClkInit.AdcClockSelection = RCC_ADCCLKSOURCE_SYSCLK;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
Error_Handler();
}
__HAL_RCC_PWR_CLK_ENABLE();
if (HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1) != HAL_OK)
{
Error_Handler();
}
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
/* SysTick_IRQn interrupt configuration */
HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
/* ADC1 init function */
static void MX_ADC1_Init(void)
{
ADC_MultiModeTypeDef multimode;
ADC_ChannelConfTypeDef sConfig;
/**Common config 
*/
hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
hadc1.Init.EOCSelection = ADC_EOC_SINGLE_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 = 1;
sConfig.SamplingTime = ADC_SAMPLETIME_2CYCLES_5;
sConfig.SingleDiff = ADC_SINGLE_ENDED;
sConfig.OffsetNumber = ADC_OFFSET_NONE;
sConfig.Offset = 0;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
Error_Handler();
}
}
/* TIM3 init function */
static void MX_TIM3_Init(void)
{
TIM_ClockConfigTypeDef sClockSourceConfig;
TIM_MasterConfigTypeDef sMasterConfig;
htim3.Instance = TIM3;
htim3.Init.Prescaler = 8000;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 100;
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
}
/** 
* Enable DMA controller clock
*/
static void MX_DMA_Init(void) 
{
/* DMA controller clock enable */
__HAL_RCC_DMA1_CLK_ENABLE();
/* DMA interrupt init */
/* DMA1_Channel1_IRQn interrupt configuration */
HAL_NVIC_SetPriority(DMA1_Channel1_IRQn, 0, 0);
 //

HAL_NVIC_EnableIRQ(DMA1_Channel1_IRQn); //Disable DMA IRQ
}
/** Configure pins as 
* Analog 
* Input 
* Output
* EVENT_OUT
* EXTI
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct;
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_RESET);
/*Configure GPIO pin : PB2 */
GPIO_InitStruct.Pin = GPIO_PIN_2;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
}

#adc #adc #stm32l4 #sampling-rate

gnu · ‎2016-08-11

Posted on August 11, 2016 at 13:23

I tried now a different approach to see if things change.

I used Timer 2 OC to trigger the ADC every 1 to 15 cycles (~1 to 188ns) and removed continuous conversion mode. The result is still the same, ~3 Msps.

I am using STM studio to see the data stored in my ADC buffer.

Note: I am working on STM32L476 Discovery board.

gnu · ‎2016-08-12

Posted on August 12, 2016 at 12:19

I have to correct myself. Well I was analyzing data of the dma destination buffer where the ADC data are stored when the CPU is stopped using the debugger. Since dma is on a separate hardware it continues to run independently like it's being said in this

https://my.st.com/public/STe2ecommunities/mcu/Lists/STM32Discovery/Flat.aspx?RootFolder=https://my.st.com/public/STe2ecommunities/mcu/Lists/STM32Discovery/STM32F4%20ADCs%20Can%20Achieve%4MSPS&FolderCTID=0x01200200770978C69A1141439FE559EB459D75800084C20D8867EAD444A5987D47BE638E0F&currentviews=697

. So the data there are not reliable.

I tried to toggle a pin at the end of conversion to see what is the actual sampling rate.

I get 51us for a buffer of 128 elements. Therefore Sampling rate = 1/ (51us/128) = 2,5Msps.

I set the timer 2 to trigger the ADC every 187,5ns (1/5ns = 5.33Msps).

Timer 2 is running at 80mhz, prescaler = 1, Period =

It seems that timer 2 is not triggering the ADC every 5 ns but like 2 times slower according to what I measured. But it can be due to other reason.

I don't know where the problem lies. Any suggestion in regard to it?

gnu · ‎2016-08-16

Posted on August 16, 2016 at 09:07

Problem solved.

Found an apparent mistake within MXCUBE. Essentially it sets auto injection bit even if it's not set by user. Some how it halves the sampling rate. This thread saved my time [DEAD LINK /public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/STM32L4%20-%20ADC%20conversion%20time%20continuous%20mode%20%2b%20DMA&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&TopicsView=https%3a//my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/AllItems.aspx&currentviews=36]STM32L4 - ADC synchronuous clock mode wrong. Thank you.

fauvarque.daniel · ‎2016-08-17

Posted on August 17, 2016 at 17:17

Thank you for reporting this issue.

A corresponding bug in the HAL library has been submitted.

In the mean time the generated code in STM32CubeMX will workaround this issue.

This workaround will be availble in the next minor release of STM32CubeMX

Regards

Daniel