Don't see DAC output for SINE wave with DMA

[Kneepatch]

Hello,

I followed a tutorial on how to generate a SINE wave using DAC and DMA that was really good. Logically it makes sense, you set up the DAC, set it to be triggered by a timer, then set up the DMA channel, set it to circular, and set it to use a table of values. Start the time and the DAC DMA, should work, right? Not working for me unfortunately, no output on the PIN PA4. Here are some screenshots of my CubeMX and a snippet of my MAIN Code:

/* Private user code ---------------------------------------------------------*/

/* USER CODE BEGIN 0 */

#define NS 128

uint32_t Wave_LUT[NS] = {

  2048, 2149, 2250, 2350, 2450, 2549, 2646, 2742, 2837, 2929, 3020, 3108, 3193, 3275, 3355,

  3431, 3504, 3574, 3639, 3701, 3759, 3812, 3861, 3906, 3946, 3982, 4013, 4039, 4060, 4076,

  4087, 4094, 4095, 4091, 4082, 4069, 4050, 4026, 3998, 3965, 3927, 3884, 3837, 3786, 3730,

  3671, 3607, 3539, 3468, 3394, 3316, 3235, 3151, 3064, 2975, 2883, 2790, 2695, 2598, 2500,

  2400, 2300, 2199, 2098, 1997, 1896, 1795, 1695, 1595, 1497, 1400, 1305, 1212, 1120, 1031,

  944, 860, 779, 701, 627, 556, 488, 424, 365, 309, 258, 211, 168, 130, 97,

  69, 45, 26, 13, 4, 0, 1, 8, 19, 35, 56, 82, 113, 149, 189,

  234, 283, 336, 394, 456, 521, 591, 664, 740, 820, 902, 987, 1075, 1166, 1258,

  1353, 1449, 1546, 1645, 1745, 1845, 1946, 2047

};

/* USER CODE END 0 */

/**

 * @brief The application entry point.

 * @retval int

 */

int main(void)

{

 /* USER CODE BEGIN 1 */

HAL_DAC_Start_DMA(&hdac, DAC_CHANNEL_1, (uint32_t*)Wave_LUT, 128, DAC_ALIGN_12B_R);

  HAL_TIM_Base_Start(&htim2);

 /* USER CODE END 1 */

 /* MCU Configuration--------------------------------------------------------*/

 

 

Any help / thoughts are appreciated!

[TDK]

Where are your initialization calls for TIM and DAC?

Does DAC work without DMA?

Is the array stored in a DMA-accessible region?

Do all HAL functions return HAL_OK?

Always include your chip number in your post.

[Amel NASRI]

Hi @TDK​,

Most probably it is the order initialization issue when generating code with STM32CubeMX.

But I totally agree with you that we need answers to your previously asked questions to conclude.

-Amel

[Kneepatch]

Thanks for the prompt reply TDK and Amel!

I am working with a STM32F469I-Discovery board.

Where are your initialization calls for TIM and DAC?

The CubeMX tool included the calls in Main.c. I'll get some screenshots or code below this reply to reference.

 /* Initialize all configured peripherals */

 MX_GPIO_Init();

 MX_CRC_Init();

 MX_DMA2D_Init();

 MX_DSIHOST_DSI_Init();

 MX_FMC_Init();

 MX_LTDC_Init();

 MX_QUADSPI_Init();

 MX_I2C1_Init();

 MX_DMA_Init();

 MX_DAC_Init();

 MX_TIM2_Init();

 MX_TouchGFX_Init();

Does DAC work without DMA?

DAC does work without DMA, I can make it generate a triangle function easily.

Is the array stored in a DMA-accessible region?

Please see my reply to Georgy below, let me know if I am missing the mark on this. But from what I can tell, it's in RAM, so I think so. 

Do all HAL functions return HAL_OK?

Yes

[Georgy Moshkin]

On some parts variables are placed in memory which does not have DMA access. What is your MCU model? Check STM..._FLASH.ld file in project files tree to see memory addresses configuration.

[Kneepatch]

When checking that file, the only thing that catches my eye is this:

_Min_Heap_Size = 0x1000 ; /* required amount of heap */

_Min_Stack_Size = 0x1000 ; /* required amount of stack */

/* Memories definition */

MEMORY

{

 CCMRAM  (xrw)  : ORIGIN = 0x10000000,  LENGTH = 64K

 RAM  (xrw)  : ORIGIN = 0x20000000,  LENGTH = 320K

 FLASH  (rx)  : ORIGIN = 0x8000000,  LENGTH = 2048K

 SDRAM (rw)   : ORIGIN = 0xC0000000, LENGTH = 16M

 QSPI (r)    : ORIGIN = 0x90000000, LENGTH = 16M

}

Here is what I see in my Build Analyzer:

Does this look like the variable is loaded into DMA accessible RAM, or do you need more information?

[Georgy Moshkin]

Your code placement is wrong, you must place HAL_DAC_Start_DMA code after

 /* USER CODE BEGIN 2 */, not /* USER CODE BEGIN 1 */ - peripherals are not initialized here yet

[Kneepatch]

That was it, thanks again!

[Clem1]

Update: Further to my previous question it seems that there is another hardware-related problem. When debugging the code the execution gets stuck at

 while((__HAL_RCC_GET_FLAG(RCC_FLAG_D2CKRDY) != RESET) && (timeout-- > 0));

 if ( timeout < 0 )

 {

 Error_Handler();

 }

...and here (when commenting out the previous lines)

SystemClock_Config();

so the DMA does not even have a chance to get set up as the program is stuck that early on! Could it be that there is a mismatch between the clock setup of the used board and the example?

******************************************************************************************

I have a follow-up question, which almost identical: I have not used any of the STM32 products, so I am quite struggling with that beast of a STM32H747, which is integrated into an STM32-based Riverdi display. I have managed so far to output single DC-values up to Vref using the DAC, but I have completely failed to make the DMA work, despite a number of examples on the internet. I cannot get my head around the datasheet, which seems to suggest that there are specific (hardware-wired) DMA channels for the DAC, but in practice, one can only work with "streams". So it seems that any of the streams can be selected and the concept of a DMA channel does not exist for the H7. I am mentioning this as some tutorials suggest that certain STM32FXX MCUs seem to require certain DMA channel numbers. But assuming that I can set up the DMA with the GUI MX tool .ioc without being an expert on the MCU's architecture I have is still a problem getting any voltage at the PA4 output. Please find the main.c code and screen-shots below. I am getting desperate here as I almost considering using the other M4 core to spit out the waveform in an endless loop, so any help is highly appreciated!

/* USER CODE BEGIN Header */

/**

 ******************************************************************************

 * @file      : main.c

 * @brief     : Main program body

 ******************************************************************************

 * @attention

 *

 * Copyright (c) 2023 STMicroelectronics.

 * All rights reserved.

 *

 * This software is licensed under terms that can be found in the LICENSE file

 * in the root directory of this software component.

 * If no LICENSE file comes with this software, it is provided AS-IS.

 *

 ******************************************************************************

 */

/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/

#include "main.h"

/* Private includes ----------------------------------------------------------*/

/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/

/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/

/* USER CODE BEGIN PD */

#ifndef HSEM_ID_0

#define HSEM_ID_0 (0U) /* HW semaphore 0*/

#endif

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/

/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

DAC_HandleTypeDef hdac1;

DMA_HandleTypeDef hdma_dac1_ch1;

TIM_HandleTypeDef htim6;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/

void SystemClock_Config(void);

static void MX_GPIO_Init(void);

static void MX_DMA_Init(void);

static void MX_DAC1_Init(void);

static void MX_TIM6_Init(void);

/* USER CODE BEGIN PFP */

#define NS 128

uint32_t Wave_LUT[NS] = {

  2048, 2149, 2250, 2350, 2450, 2549, 2646, 2742, 2837, 2929, 3020, 3108, 3193, 3275, 3355,

  3431, 3504, 3574, 3639, 3701, 3759, 3812, 3861, 3906, 3946, 3982, 4013, 4039, 4060, 4076,

  4087, 4094, 4095, 4091, 4082, 4069, 4050, 4026, 3998, 3965, 3927, 3884, 3837, 3786, 3730,

  3671, 3607, 3539, 3468, 3394, 3316, 3235, 3151, 3064, 2975, 2883, 2790, 2695, 2598, 2500,

  2400, 2300, 2199, 2098, 1997, 1896, 1795, 1695, 1595, 1497, 1400, 1305, 1212, 1120, 1031,

  944, 860, 779, 701, 627, 556, 488, 424, 365, 309, 258, 211, 168, 130, 97,

  69, 45, 26, 13, 4, 0, 1, 8, 19, 35, 56, 82, 113, 149, 189,

  234, 283, 336, 394, 456, 521, 591, 664, 740, 820, 902, 987, 1075, 1166, 1258,

  1353, 1449, 1546, 1645, 1745, 1845, 1946, 2047

};

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**

 * @brief The application entry point.

 * @retval int

 */

int main(void)

{

 /* USER CODE BEGIN 1 */

 /* USER CODE END 1 */

/* USER CODE BEGIN Boot_Mode_Sequence_0 */

 int32_t timeout;

/* USER CODE END Boot_Mode_Sequence_0 */

/* USER CODE BEGIN Boot_Mode_Sequence_1 */

 /* Wait until CPU2 boots and enters in stop mode or timeout*/

 timeout = 0xFFFF;

 while((__HAL_RCC_GET_FLAG(RCC_FLAG_D2CKRDY) != RESET) && (timeout-- > 0));

 if ( timeout < 0 )

 {

 Error_Handler();

 }

/* USER CODE END Boot_Mode_Sequence_1 */

 /* MCU Configuration--------------------------------------------------------*/

 /* Reset of all peripherals, Initializes the Flash interface and the Systick. */

 HAL_Init();

 /* USER CODE BEGIN Init */

 /* USER CODE END Init */

 /* Configure the system clock */

 SystemClock_Config();

/* USER CODE BEGIN Boot_Mode_Sequence_2 */

/* When system initialization is finished, Cortex-M7 will release Cortex-M4 by means of

HSEM notification */

/*HW semaphore Clock enable*/

__HAL_RCC_HSEM_CLK_ENABLE();

/*Take HSEM */

HAL_HSEM_FastTake(HSEM_ID_0);

/*Release HSEM in order to notify the CPU2(CM4)*/

HAL_HSEM_Release(HSEM_ID_0,0);

/* wait until CPU2 wakes up from stop mode */

timeout = 0xFFFF;

while((__HAL_RCC_GET_FLAG(RCC_FLAG_D2CKRDY) == RESET) && (timeout-- > 0));

if ( timeout < 0 )

{

Error_Handler();

}

/* USER CODE END Boot_Mode_Sequence_2 */

 /* USER CODE BEGIN SysInit */

 /* USER CODE END SysInit */

 /* Initialize all configured peripherals */

 MX_GPIO_Init();

 MX_DMA_Init();

 MX_DAC1_Init();

 MX_TIM6_Init();

 /* USER CODE BEGIN 2 */

 HAL_DAC_Start_DMA(&hdac1, DAC_CHANNEL_1, (uint32_t*)Wave_LUT, 128, DAC_ALIGN_12B_R);

 HAL_TIM_Base_Start(&htim6);

 /* USER CODE END 2 */

 /* Infinite loop */

 /* USER CODE BEGIN WHILE */

 while (1)

 {

  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */

 }

 /* USER CODE END 3 */

}