STM32 F303RE USB DMA conflict

[lkaino]

Posted on June 11, 2016 at 18:31

Hello,

I started using USB CDC device in my project which uses F303RE controller. I struggled to get it working until I realized that it is most likely using same DMA channel that I'm using for SPI3 access. I'm using DMA2 channels 1 and 2 for that.Where can I find information of which DMA channel the USB CDC device is using, and is it possible to disable it? Most likely I don't want to disable it as it would eat up the processor cycles. I tried searching from ST documentation and the CDC device source code but couldn't find the used DMA channel. Only reference that I found from ST documentation is that it uses some internal DMA in HS mode. 

[slimen]

Posted on June 13, 2016 at 20:49

Hi,

You can refer to the

http://www.st.com/content/ccc/resource/technical/document/reference_manual/4a/19/6e/18/9d/92/43/32/DM000435pdf/files/DM000435pdf/jcr:content/translations/en.DM000435pdf

, in the section (5.7 DMA register map) which defined the DMA register map. Also, you can have a look to this

/content/ccc/resource/technical/document/user_manual/cf/38/e5/b5/dd/1d/4c/09/DM00108pdf/files/DM00108pdf/jcr:content/translations/en.DM00108pdf

:STM32Cube USB device library. May be this example under the

/content/my_st_com/en/products/embedded-software/mcus-embedded-software/stm32-embedded-software/stm32cube-embedded-software/stm32cubef3.license=1465820663html

package, can help you to develop your application:STM32Cube_FW_F3_V1.5.0\Projects\STM32303C_EVAL\Applications\USB_Device\CDC_Standalone This application exampleshows how to use the STM32F3xx USB device application based on the CDC. So, you'll still have to own the integration with this applicationand get inspiration to achieve you goal. Regards

[slimen]

Posted on June 14, 2016 at 15:20

Hi,

Following the 

http://www.st.com/content/ccc/resource/technical/document/reference_manual/4a/19/6e/18/9d/92/43/32/DM00043574.pdf/files/DM00043574.pdf/jcr:content/translations/en.DM00043574.pdf

, Table 79 (page 276) we don't have DMA requests for USB.

But, could you please confirm that USB works as expected when you disable SPI3 ?

I think we need more details to understand your issue.

 Regards