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problem modifying SD example (can't speed up reading)

 
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micro_newbie



Joined: 20 Dec 2008
Posts: 2

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problem modifying SD example (can't speed up reading)
PostPosted: Sat Dec 20, 2008 3:15 pm     Reply with quote

Hi,
I'm working with CCS's "3.3V Ethernet Controller Development Kit" and with the code examples supplied by CCS. I've tried to increase the number of readings from the sd card per minute by changing the spi to hardware control in the mmcsd.c (based on the ex_mmcsd Example but trying to read a 64 byte block with read_data()), but no use.
Can anyone give some pointers about speeding up read time from the sd or even point me to an example?
micro_newbie



Joined: 20 Dec 2008
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can somebody help me
PostPosted: Tue Dec 30, 2008 2:28 am     Reply with quote

can somebody help me
forgot to add this information on my privies message
Version of your compiler 4.073
Target PIC Microcontroller PIC18f67j60
Debug Mode
Target voltage 9v
ckielstra



Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands

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PostPosted: Tue Dec 30, 2008 8:22 am     Reply with quote

When you say it is slow try to be more exact. What reading speed are you getting and how fast do you need it to be?
What is the clock frequency of your PIC?
What does the setup code for your SPI configuration look like?

Have a look at http://www.ccsinfo.com/forum/viewtopic.php?t=33497
In this thread the read from 260kB/s was increased up to 540kB/s (PIC18F67J50 @ 48MHz, 12MHz SPI-Freq.)
This is about the fastest reading speed you will get on a PIC18 in SPI mode. For higher read speeds you'll have to change your hardware and use the 4-bit SD-bus mode.

Try implementing the code or suggestions mentioned in the above thread and when you have problems post your code and questions in this thread.
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