RTEMS BSD Net on Atmel SAM Board

[Isaac Gutekunst]

Hi Pavel,

This information is quite helpful. Thank you!

Isaac
On 06/06/2016 04:36 AM, Pavel Pisa wrote:
> Hello Isaac,
>
> On Thursday 02 of June 2016 17:09:31 Isaac Gutekunst wrote:
>> On 06/01/2016 07:18 PM, Pavel Pisa wrote:
>>> Hello Isaac,
>>>
>>> On Wednesday 01 of June 2016 23:09:39 Isaac Gutekunst wrote:
>>>> I believe I solved all my problems. Not enough memory. After updating
>>>> the linker script to use SDRAM, everything appears to be working well!
>>>> (Knock on wood).
>>>
>>> I think that SAM V71 setup with 2 MB of external SDRAM is not much
>>> above minimal limit for use of RTEMS with BSD networking.
>>> If the single chip solution with only 128kB of internal SRAM
>>> is considered (may be with additional 128kB which can be borrow
>>> for some buffer from the instruction TCM) then it cannot
>>> be used with libBSD based networking. So it would worth
>>> to consider lwIP. I hope that it would be integrated to
>>> the RTEMS file operations API as part of this year GSoC.
>>> So this option worth to be considered to support
>>> networking on the small systems.
>>
>> Hi Pavel,
>>
>> Thanks for the info.
>>
>> We will definitely be adding the largest SDRAM chip we can find to our
>> final board, so I imagine we will be okay.
>>
>> Based on the weirdness I've experienced, not having enough RAM doesn't
>> necessarily result in a nice error message. What do you think is a good
>> amount of RAM to give the stack, and how can I be sure it's enough?
>
> I have no experience with libBSD on RTEMS. But I would expect that
> mentioned 2 MB are minimum for stack of this level/complexity.
> When I compare that with Linux then 8 MB SDRAM has been successfully
> used in many wireles routers etc. It has been minimum and I consider
> that it is not enough for latest kernel versions and full GLibC.
> Then 32 MB is OK for Linux.
>
> I expect that 8 MB should be OK for RTEMS and libBSD but some
> statistic about amount of allocated memory for example for
> 4 and 10 TCP/IP connections from Chris or Sebastian would
> be interresting. From my experience with LPC, we have
> found that 512 kB of Flash is too small for complete
> system code+initialization data if we want full RTEMS
> support for networking (TCP, TFTP, remote shell)
> even if we have 32 MB of external SDRAM.
> 1 MB of Flash should be enough for reasonable size application.
> 2 MB even for larger application.
>
> As for classical RTEMS stack, it has lower memory demand
> then libBSD, so I expect that 2 MB would be probably OK.
>
> As for lwIP, we have some experience with TMS570.
> 1 or 2 MB of Flash is OK. 256 kB of internal SRAM
> is OK for something like 4 to 10 TCP/IP connections.
>
> Best wishes,
>
>              Pavel
>
>
>
>