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[lwip-users] Delay fixes dropped packets

From: JM
Subject: [lwip-users] Delay fixes dropped packets
Date: Sat, 8 Aug 2009 20:17:43 -0700 (PDT)

I'm using lwIP on a Stellaris micro, and saw lots of dropped packets.  Upon further investigation, it turns out these packets were failing TCP checksum.  I noticed that if I enabled debugging in the correct areas, and enough of it, the issue went away.  Long story short, after lots of trial and error I discovered that if I disable debugging and add a delay of 300us at the very end, before the return, in ip_output_if(), it fixes the problem.  If I decrease the delay, the problem starts appearing and becomes worse as I continue to decrease the delay. 

The driver for the onboard ethernet controller is from the Luminary driver library.  I don't imagine that a very high percentage of users here use the same chip I'm using, but generally speaking, any idea what I can look for; what would cause this?  I'm mainly recieving data.  It's streaming audio data so once I initiate it, the stack only has to ACK. 

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