SD card speed optimization 18f2550

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Pripyat
Posts: 1
Joined: 29 Aug 2010 14:51

SD card speed optimization 18f2550

#1 Post by Pripyat » 29 Aug 2010 15:06

I have several general questions:

1) How much faster are A/D conversions if I perform them myself based on the calculations from the datasheet? Or does the function perform these calculations per the datasheet?

2) I am using this command:

Code: Select all

while(1) {
   WordToStr(ADC_Read(0), file_contents);
   Mmc_Fat_Write(file_contents, _FILE_CONTENTS_SIZE);
   }
I am using an external 8MHz oscillator. When I set the clock to 48 Mhz I am getting strange output. When I bump it down to 32 Mhz, the output is accurate. I was under the impression that the SD library function Mmc_Fat_Write() would take care of the Wait states no matter what the clock speed is set at.

3) In short, in what ways can I optimize the speed at which I can get the ADC_Read() values to the card?

[edit] I should add that at 32MHz I am getting ~ 40 writes/second.

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anikolic
mikroElektronika team
Posts: 1775
Joined: 17 Aug 2009 16:51
Location: Belgrade
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Re: SD card speed optimization 18f2550

#2 Post by anikolic » 30 Aug 2010 10:25

Hello Pripyat,

Can you please either share your zipped demonstration project folder, that causes this behavior, or open a Support ticket for private investigation.
We have to eliminate every option, and recreate the error in the original environment, with your configuration bits, and other code parts that could affect code execution.

Thank you!

Best regards,
Aleksandar
Web Department Manager

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