Hi Paul!
It seems that at least on the 1768 the descriptors and buffers have to
be located in the same block. This fixed my problem....
Jan
On 28.11.2014 21:02, Paul Webber wrote:
> I just finished implimenting 1.41 on the LPC 4078 using parts of the NXP
> examples. The DMA for the MAC works only with the 32K (in the LPC 4078)
> block. I used the linker file to make sure nothing else ended up in that
> memory block. Also if you are using the example provided by NXP there are
> other things in that memory block, descriptors for the DMA and extra buffers.
>
> Paul
>
> ________________________________________
> From: [email protected]
> <[email protected]> on behalf of Simon
> Goldschmidt <[email protected]>
> Sent: Friday, November 28, 2014 4:03 AM
> To: [email protected]
> Subject: Re: [lwip-users] LPC1768 lpc_low_level_input: Packet dropped
> witherrors (0xffffffff)
>
> Jan Menzel wrote:
>> On 28.11.2014 03:07, Grzegorz Niemirowski wrote:
>>> 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.
>
> I don't know the LPC1768, but a quick look at the LPC1769/68/67/66/65/64/63
> Datasheet brings up this:
>
> --- snip ---
> On-chip SRAM includes:
> - 32/16 kB of SRAM on the CPU with local code/data bus for high-performance
> CPU access.
> - Two/one 16 kB SRAM blocks with separate access paths for higher throughput.
> These SRAM blocks may be used for Ethernet, USB, and DMA memory, as well as
> for general purpose CPU instruction and data storage.
> --- snap ---
>
> To me, this implies the first SRAM block is for CPU-only storage (like stack,
> state info, etc) and cannot be used for DMA.
>
>
> Simon
>
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