Using LwIP on the STM32H7

[Robin Müller]

Thanks for the clarifications. Now I actually understand what the
MPU_Config call from the STM32 example does. I was not sure what that was
for. I reintroduced the lwip sections (from my first mail9
again with the values from the STM32 linker script and used the MPU_Config
call from the STM32 example.
It is now not crashing anymore. I still can't receive UDP packets, but at
least I am now able to run my polling loop.

Kind Regards
Robin Müller



On Thu, 28 Jan 2021 at 18:33, Mr. Andrei Chichak <groups at chichak.ca> wrote:

> Good morning,
>
> I’ve been trying to get ethernet on STM32F7 going using the bsd networking
> stack (not going that well, there is a LOT of undocumented knowledge to
> straighten out).
>
>
> The STM32x7 ethernet controllers need their descriptors and data areas to
> be located on 32-byte boundaries with a combination of cache being turned
> off and buffering being turned off. This is a side effect of the STM32x7
> DMA and data caching.
>
> The examples that ST have for LWiP under FreeRTOS have some issues with
> the linker file having overlapping sections and the stack (above the ETH
> data areas) being left with no cache and no buffering. The space above the
> rx/tx buffers is also less than the stack space minimum specified in the
> linker file as well.  Some rearranging of the ETH descriptors and data
> areas would be prudent. Like push them to the top of SRAM and locate the
> stack below.
>
> To get this all going, they set up the MPU for two overlapping sections,
> one being the top 16kB of SRAM and the other the 256B that contain the ETH
> descriptors. I believe the MPU regions can be set in increments of 32Bytes,
> so setting up the cache and buffering should be do-able without affecting
> the stack.
>
>
>
> In RTEMS it appears that I have to pull the data and lengths out of some
> mbufs (I had to look that up), and push it all into the data areas. Using
> LWiP, I think you do similar things, just pulling the data out of the pbuf
> chains.
>
> On the STM forums is an item about how to actually get a working ETH going
> on ST processors. There’s all sorts of issues including Cube generating
> code for ST’s dev boards that has the incorrect address for the PHY chip.
> Take a look at:
> https://community.st.com/s/question/0D50X0000BOtfhnSQB/how-to-make-ethernet-and-lwip-working-on-stm32
>
> More later,
>
> Andrei
>
>
>
> ---------------------
> Andrei Chichak
>
> Systems Developer
> CBF Systems Inc.
> 225 College Plaza
> 8215 112 Street.
> EDMONTON, ALBERTA
> T6G 2C8
> CANADA
>
> Phone: 780-628-2072
> Skype: andrei.chichak
>
>
>
>
>
>
>
>
>
>
>
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