STM32H7R/S: How to configure an ADC DMA transfer in circular mode using STM32CubeMX

CMYL · ‎2024-11-27

Summary

This article provides a step-by-step guide on how to configure your STM32H7R/S to transfer ADC converted values in DMA circular mode using STM32CubeMX (version 6.12 is used).

For a complete firmware example, refer to the attached project at the end of the article.

1. Step-by-step

Step 1: Navigate to the [Board Selector] (optionally use the BSP to configure LEDs, user button and virtual com port "VCP")

Step 2: Choose [Appli] and [Boot] projects generation, as we’ll put the application code into an external memory, refer to this KB article for complete project configuration.

Step 3: Select [ADC1] and assign it to [Appli] project.

Step 4: Enable the ADC channels that you need (4 channels are enabled here).

Step 5: Configuration

Set [Continuous conversion mode] to [Enable]. This option loops the ADC. When the ADC finishes converting all its channels, it will start again from the beginning.
Set [Enable Regular Conversions] to [Enable].
Configure ADC 1: Set [Conversion Data Management Mode] to [DMA Circular Mode].
After the ADC converts value, it will create a request for the DMA. Circular mode here means that after the ADC finishes all the regular channels, it continues to generate DMA requests in the next run.
Set the [Number of conversion] to [4] (or your preferred value). This will set ADC to do 4 ADC
conversion which we can set.

Step 6: Choose the sequence. You can set the ADC channel for each rank. Each rank is assigned one ADC channel to convert. It's possible to select the same channel each time.

Step 7: Go to the HPDMA settings.

Select [CH0]
Set [Circular Mode] to [Enable]
Set [Request] to [ADC1]
Set [Source Data Settings] data width to [Half Word]
Set [Destination Data Settings] data width to [Half Word]
Set [Destination Data Settings]
Set [Destination Address Increment After Transfer] to [Enable]

Step 8: Generate the code.

Create a table of size 64 (or a multiple of 8, for example).

As the processor is a Cortex®-M7, place the table into noncacheable region (ITCM/DTCM memories (@0x0000000/@0x20000000: Not cacheable and only accessible by the Cortex® M7 and the GPDMA/HPDMA).

If the application needs to put DMA buffers in AXI SRAM (starting from @0x24000000), the user must:

Define a noncacheable region in the MPU and linker configuration file to locate
DMA buffers (this is our choice in this example).
Ensure cache maintenance operations to ensure the cache coherence between the
CPU and the DMAs.
Disable the DCACHE (not recommended).

Find the pseudo-code below:

/* USER CODE BEGIN PD */
#define ADC_CONVERTED_DATA_BUFFER_SIZE 64
/* USER CODE END PD */
/* USER CODE BEGIN PV */
__IO uint16_t uhADCxConvertedData[ADC_CONVERTED_DATA_BUFFER_SIZE]
__attribute__((section("noncacheable_buffer")));
/* USER CODE END PV */
/* USER CODE BEGIN PFP */
static void MPU_AdjustRegionAddressSize(uint32_t Address, uint32_t Size,
MPU_Region_InitTypeDef* pInit);
static void MPU_Config(void);
/* USER CODE END PFP */
int main(void)
{
MPU_Config(void);
….
HAL_ADC_Start_DMA(&hadc1,
(uint32_t *)uhADCxConvertedData,
ADC_CONVERTED_DATA_BUFFER_SIZE
)
…
…
}
….

For a complete firmware example, refer to attached project.

2. Test results

Results in the debug windows are continuously updated as the ADC DMA transfer is in a circular mode. To check the converted values from the table, suspend the debug and analyze the result from the debug watch window.

STM32H7R/S: How to configure an ADC DMA transfer in circular mode using STM32CubeMX

Summary

1. Step-by-step

2. Test results

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