Re: [lwip-users] Windows 7 Startup crashes LwIP and Free RTOS

[Marco Jakobs]

Hi all,

i reverted in having some looks to it again. Having a deeper look at the 
EMAC driver task (Richard ;-) ), i see really nothing which may cause 
the system to hang. The interrupt just sets the semaphore, and the EMAC 
task reads out all the EMAC buffers if it is triggered by the semaphore.

I discovered this article: 
http://www.zsoltmolnar.hu/blog/embedded/2006_04_01_archive.html and i 
have discovered that RXUBR is not handled by the interrupt. However, 
this should not cause that problems, as - even if the Rx inperrupt is 
missing, the EMAC driver waits maximum 100 tics for the semaphore and 
checks the receive buffers again; the system will not hang due to this. 
But i added the RXUBR to also cause an interrupt and trigger the semaphore.

But let's discuss overruns. When i'm not getting the data fast enough 
out of the 16 available EMAC buffers, the EMAC encounters an overrun. 
Nothing should happen, if all buffers are owned by the software, the 
EMAC will discard the frame. There is no overrun code in the EMAC 
driver, the packet is gone and finish. So:

Question one:
What is the behaviour of LwIP in that case, if there are still some 
frames of the packet in the EMAC buffers but some other frames are 
missing due to the EMAC threw them away because of an overflow?

Question two:
Is there any action needed if the EMAC sets the receive overflow bit?

Thanks for any suggestions
Marco