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Re: [lwip-users] LPC1768 lpc_low_level_input: Packet dropped witherrors

From: Jan Menzel
Subject: Re: [lwip-users] LPC1768 lpc_low_level_input: Packet dropped witherrors (0xffffffff)
Date: Fri, 28 Nov 2014 09:17:57 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0

On 28.11.2014 03:07, Grzegorz Niemirowski wrote:
> Jan Menzel <address@hidden> napisal(a):
>> Hi all!
>> It seems that I've found the problem now. For anyone facing the same
>> issue: I have changed the linker script and positioned the buffer
>> descriptors and the receive buffers into the same RAM block. Before this
>> the linker had placed the buffer descriptors in SRAM (0x1000xxxx) and
>> the buffers in AHB-SRAM (0x2007xxxx).
>> Any clue why that matters?
> Does your low level driver use DMA? Is AHB-SRAM accessible by DMA?
Yes, all memory is accessible via DMA. IIRC datasheet says that flash
can not be used with EMAC.
        To my knowledge, the LPC EMAC can not be operated without DMA. One has
to provide buffer descriptors which contain pointer to buffers and
sizes. The EMAC searches this descriptors for a free buffer to store
incoming packets.


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