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Re: [lwip-users] Randomly delayed frame (STM32070 package including LwIP

From: address@hidden
Subject: Re: [lwip-users] Randomly delayed frame (STM32070 package including LwIP v1.4.1)
Date: Fri, 4 Jan 2019 22:33:45 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

Am 04.01.2019 um 21:15 schrieb stevestrong:
Jason, thanks for your comment.

I saw that no Rx packets were ever lost, no Rx/TX buffer over- or under-flow
ever occurred.
That finally made me think on DMA and PHY.
I realized that currently my PHY works in 100Mbp half-duplex mode, and that
could eventually be a problem, when many packets arrive and the PHY tries to
send some data in the same time (although the PHY should probably manage

Actually, it is the MAC that has to handle half-duplex retransmission, not the PHY. The PHY can report "half duplex" via MDIO as a result of autonegotiation, but if the MAC is not set to half duplex, too, you'll get lost TX packets.


Then I found on Internet a site which offers a solution for DP83848, a patch
for MBED ETH lib, to work in full-duplex mode.

I implemented it, and ... voila: no more lost packets in 100 tries!
No more delayed packets. Success!

So I can conclude that the issue was most probably due to the heavy traffic
when PHY is working in half-duplex mode.
Does this make sense?

Anyway, thank you all for the invested time and effort, I really appreciate


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