DCMI With DMA ON STM32H743

[drJonesy]

Hi 

 

I am using a custom board to run a stm32h743 with a ov5640 camera. There is external ram fitted, the camera sets up correctly using i2c, and i can run the capture

HAL_DCMI_Start_DMA(&hdcmi,DCMI_MODE_SNAPSHOT,(uint32_t)pFrameBuffer, (512 * 1024) / 4);

 

However what i am getting in the buffer is just repeated garbage.

 

 

is there any help you can give or at least something to look at.

 

 

[KDJEM.1]

Hello ​@drJonesy ;

 

Could you please give more details like image size?

In snapshot mode, the DMA must ensure the transfer of one frame (image) from the DCMI to the desired memory:

• If the image size in words does not exceed 65535, the stream can be configured in normal mode.
•  If the image size in words is between 65535 and 131070, the stream can be configured in double buffer mode.
• If the image size in words exceeds 131070, the stream cannot be configured in double-buffer mode.
   

For that I recommend you to look at AN5020 Section 6.4.6, Section 6.4.8 and Section 6.4.9 to check the DMA configuration.

Also you can refer to  8.3 DCMI examples based on STM32CubeMX section in AN5020 and get inspired. This section details the following typical examples of DCMI.

I hope this help you!

 

Thank you.

Kaouthar

[drJonesy]

The ov5640 is configured in jpeg mode at the moment.

[KDJEM.1]

Hello ​@drJonesy ,

 

Are you using a embedded synchronization mode or a  the hardware synchronization?

Because, for compressed data (JPEG), the DCMI supports only the hardware synchronization.

 

Thank you.

Kaouthar