>On Thu, 03 Feb 2011 07:24:34 -0600, "sanaas"
><sanaashaukat@n_o_s_p_a_m.hotmail.com> wrote:
>
>>Hi everybody, 
>>
>>I have interfaced a 4 GB class 4 Kingston micro SD card with MPC5554
using
>>SPI. I have implemented FAT32 file system driver on it.
>>Everything(reading/writing files) works fine when I keep SPI clock at 3
MHz
>>after initialization. With 3 MHz clock I am able to write 1 MB of data in
a
>>file in 1 min which is pretty low speed!! 
>>But when I turn to SPI clock above 3 MHz, the SD card does not
read/write
>>sectors at all!! All I want to do is to increase this speed of data
>>transfer.
>>Has any body done such a thing with speed higher than 3 MHz? I would be
so
>>grateful if any body could help me in this issue as I have been trying
to
>>solve this issue since last so many days but in vain and my FAT32 driver
>>would be of  no use in my application with such a low speed.
>>


Thanks for showing interest in solving my problem and for your
suggestions.
You are right that there should be buffering but people have achieved
speeds in hundreds of KB/s using SD card without using any buffer.My speed
is not even 50KB/s!!
I do have an oscilloscope and I have observed the signals multiple times.
There is no ringing effect as such and you are right that the power supply
and controller should be as close as possible to SD card for high frequency
operation but I am working on a card which is already designed and
manufactured accordingly, so I cannot move any thing!! Well my issue is
still unsolved. Although i am able to run it now at 12.5 MHz speed but
first of all it does not responds in one go and secondly at this speed card
responds too late when I write a sector to it so there is only a few
seconds speed difference between the two. I am trying to solve the issue by
observing SPI signals clk,data in and out etc.	   
					
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On Thu, 03 Feb 2011 07:24:34 -0600, "sanaas"
<sanaashaukat@n_o_s_p_a_m.hotmail.com> wrote:

>Hi everybody, 
>
>I have interfaced a 4 GB class 4 Kingston micro SD card with MPC5554 using
>SPI. I have implemented FAT32 file system driver on it.
>Everything(reading/writing files) works fine when I keep SPI clock at 3 MHz
>after initialization. With 3 MHz clock I am able to write 1 MB of data in a
>file in 1 min which is pretty low speed!! 
>But when I turn to SPI clock above 3 MHz, the SD card does not read/write
>sectors at all!! All I want to do is to increase this speed of data
>transfer.
>Has any body done such a thing with speed higher than 3 MHz? I would be so
>grateful if any body could help me in this issue as I have been trying to
>solve this issue since last so many days but in vain and my FAT32 driver
>would be of  no use in my application with such a low speed.
>
>Thanks,
>Sana

IIRC you need a fair bit of buffering to get high throughput on an SD
card.. even fast cards go away for significant stretches of time, like
a hundred ms or more. 

In article <KMadnZ_gpIMPMdfQnZ2dnUVZ_uidnZ2d@giganews.com>, 
sanaashaukat@n_o_s_p_a_m.hotmail.com says...
> Hi everybody, 
> 
> I have interfaced a 4 GB class 4 Kingston micro SD card with MPC5554 using
> SPI. I have implemented FAT32 file system driver on it.
> Everything(reading/writing files) works fine when I keep SPI clock at 3 MHz
> after initialization. With 3 MHz clock I am able to write 1 MB of data in a
> file in 1 min which is pretty low speed!! 
> But when I turn to SPI clock above 3 MHz, the SD card does not read/write
> sectors at all!! All I want to do is to increase this speed of data
> transfer.
> Has any body done such a thing with speed higher than 3 MHz? I would be so
> grateful if any body could help me in this issue as I have been trying to
> solve this issue since last so many days but in vain and my FAT32 driver
> would be of  no use in my application with such a low speed.
> 

While I am no SPI expert by any means, I have used a LOT of SPI 
peripherals with nary a problem.  I would say you need to start digging 
out the test equipment and look at what is REALLY going on.  A scope to 
make sure your signals are clean and not ringing/bouncing all over the 
place is a good start.  Does the card have decent power supply 
decoupling as close to the SD connector as possible?  Is your SPI really 
working at the speeds you think?  Is it operating in the mode that you 
think?  Is the chip select signal active when it should be?  All things 
you need to find out.  So, a scope and maybe a logic analyzer would be 
called for and some testing is in order.

Hi everybody, 

I have interfaced a 4 GB class 4 Kingston micro SD card with MPC5554 using
SPI. I have implemented FAT32 file system driver on it.
Everything(reading/writing files) works fine when I keep SPI clock at 3 MHz
after initialization. With 3 MHz clock I am able to write 1 MB of data in a
file in 1 min which is pretty low speed!! 
But when I turn to SPI clock above 3 MHz, the SD card does not read/write
sectors at all!! All I want to do is to increase this speed of data
transfer.
Has any body done such a thing with speed higher than 3 MHz? I would be so
grateful if any body could help me in this issue as I have been trying to
solve this issue since last so many days but in vain and my FAT32 driver
would be of  no use in my application with such a low speed.

Thanks,
Sana


	   
					
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