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Re: SV: [lwip-users] Odd byte packets in LWIP

From: Andreas Zippel
Subject: Re: SV: [lwip-users] Odd byte packets in LWIP
Date: Tue, 11 Nov 2003 16:45:42 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; de-AT; rv:1.2.1) Gecko/20021204 
Hi
i rewrote the code of the cs8900 driver to accept odd payload length and do a byte transfer in this case. this solution help me very good but with the tradeoff that the throughput goes down a little bit. but it works. 

regards andreas

Jan Wester wrote:

Hi
We have also tested CS8900, we solved the problem by adding a 2k buffer to read out all payloads to and sened that to the controller. 
You can't add space to you payloads, it corrupt your data
//Jan

    -----Ursprungligt meddelande-----
    *Från:* address@hidden
    [mailto:address@hidden *Nishen Naidu
    *Skickat:* den 11 november 2003 13:00
    *Till:* Mailing list for lwIP users
    *Ämne:* Re: [lwip-users] Odd byte packets in LWIP

    Hi,
I'm using a c8900 ethernet chip and I do know it 
    has a problem wit odd length packets.
    Any idea what a solution to this problem might be?
    Do you automatically make all the packets you send out even length?
    I could not do this since the client on the other side requires the
    packet
    length to be correct i.e. odd in this case.
    The packets get sent out correctly if I make the packet even just
    before I call
    the netconn_write, but I don't want to do it this way due to the
    above reason.
    If I make the 'frame length' in the ethernet driver fot lwip even
    then the packets
    still do not get send correctly.
    Any ideas?
Thanks 
    Nishen
----- Original Message ----- 
    *From:* Jan Wester <mailto:address@hidden>
    *To:* Mailing list for lwIP users <mailto:address@hidden>
    *Sent:* Tuesday, November 11, 2003 11:31 AM
    *Subject:* SV: [lwip-users] Odd byte packets in LWIP

    Hi
    I had problem with odd length in the driver for Ethernet Controller,
    depending on the hardware how the Ethernet Controller is connected
    to the processor.
    We use ARM with Davicom Ethernet Controller.
    We also got problem with odd startaddress for buffer, but I think
    what is ARM specific.
    file://Jan

        -----Ursprungligt meddelande-----
        *Från:* address@hidden
        [mailto:address@hidden
        *Nishen Naidu
        *Skickat:* den 11 november 2003 07:29
        *Till:* Mailing list for lwIP users
        *Ämne:* [lwip-users] Odd byte packets in LWIP

        Hi
I'm having a problem sending out packets of odd length on 
        certain occasions.
        Does lwip work well with odd length packets?
        I read the following comment in some lwip sample code:
        /*
Important!!! LwIP data alignment issue: 
           As of now LwIP code does not handle odd byte length packets
        properly. So round packets to even byte
           length by adding space characters (' '). This is true only
        for processors that cannot handle
           mis-aligned memory access.
*/ 
        is this correct??
Thanks 
        Nishen

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