sd card read-modify-write back. possible?

giannissam · 2009-03-10 21:35

Hi all.
I've been searching the forum for some days and i cant find a way to read a file from an sd manipulate it and write it back to sd.
Porthos os says it can copy files but i cant see the "copy" routine in the spin code

is there a way to do it?
thanx in advance.

Post Edited (giannissam) : 3/10/2009 10:43:53 PM GMT

Chris Savage · 2009-03-10 21:37

Read-Modify-Write doesn't isn't really read/write at the same time. Your subject is a little misleading.

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Chris Savage
Parallax Engineering

giannissam · 2009-03-10 21:43

Sorry. i changed it.

mctrivia · 2009-03-10 22:10

check out http://obex.parallax.com/objects/92/ I have used this with great suces reading files off uSD cards on my modules. I know it can write also just have not played with that yet

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Oldbitcollector (Jeff) · 2009-03-10 22:16

Here's a thread with a little tutorial that might help too

http://forums.parallax.com/showthread.php?p=747794

OBC

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giannissam · 2009-03-16 23:57

hello again.
i tried to make a file-copy program (attached).
Steps:

1. Read the source file character by character.
2. Save each character temporarily in a variable (read_buf)
3. Close the source file
4. At the first time open the target file in write mode and then append mode. Each time writing the read_buf contents.

Good thing: it works for small text files
Bad thing: you better make plans for the next week (or perhaps a month) before trying to copy more than 5Mbytes

I tried to copy a wav file (windows xp start up sound) in mono (about 212Kb) and it took several hours to copy 14Kb

thinking to make read_buf bigger (to store more characters) in order to have less openings and closings of files.

Any ideas?
can "Pread" and "Pwrite" routines be used for my perpose?

thx in advance.

Harrison. · 2009-03-17 00:47

Try using the modified fsrw object I posted here: http://forums.parallax.com/showthread.php?p=751612.

Rayman · 2009-03-17 01:12

Nice one Harrison! I was hoping someone would tackle the multiple files from SD problem...

giannissam · 2009-03-17 11:39

Can you please give me some info for your code?
what does Fullduplexserial do?

sd card read-modify-write back. possible?

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