[En-Nut-Discussion] SD card perf issue on EIR

[uprinz2 at netscape.net]

Hi Mathieu, 
 
I didn't do anything with SD on my EIR so far. So I never checked for 
proper configuration of that part. But I know that Nut/OS is using a 
combination of hardware and software interfacing on the SPI bus. So, while 
using interrupt driven SPI, the chipselects are done by GPIO. There is a 
two-step improvement possible for that. 
First speed-up is possible by exchanging every NutGpioCfg() by its 
appropriate direct access outr(GPIO_xy, value). 
Second it is possible to configure the SPI interface to directly drive the 
chipselects by hardware. For that some real deep changes have to be 
implemented. Additionally one has to respect some problematic 
constellations given by the chips errata sheet. 
 
In general SD-Access should be done with DMA/PDC and then there are another 
one or two erratas to be obeyed. 
 
I am not sure if I am actually the only one experimenting with the EIR in 
this list ( besides Harald). This is the first support request on EIR since 
the few month I have the device. But I am actually busy with the http 
frontend of it. SD was on my list for a later date. 
 
Best regards, Ulrich 
 
On Mon, 8 Feb 2010 00:20:10 +0100, Mathieu SOULARD <kazh29 at gmail.com> 
wrote: 
> Hi all, 
>  
> I'm facing performances issues using SD cards on my EIR board powered by 
> nut/os 4.8.6. 
>  
> It seems that I can read a file about 10Ko/seconds, which is not enough 
to 
> feed the audio codec with data. 
> The SD card is formated in FAT32. 
>  
> I would like to know someone has experienced such issue, and if you know 
> what could I do to improve it ? 
>  
>  
> Thanks 
> Regards 
>  
> Mathieu 
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