fat.c + mmcsd.c Working but Windows can't read the files

[CoverUp]

I'm using a PIC18f4525 and the fat.c + mmcsd.c library.
Everything works good on PIC.
I can initialize the SD card, format the card, make a file and append data to it.
I can read all the data written...very happy so far.
BUT
Then I put the SD card in a PC running Windows XP and the directory appears to be empty... but if you see the properties of the disk, there's 17mb used (my data written with the PIC).

I'm using a Kingston 2GB SD card.

Any idea what could be wrong??

I format the SD card from pic.. everything work but Windows can read the directory listing

Then I format from Windows using FAT32.. again the PIC can write and read, but nothing appears on Windows.
:(


PD: English is not my native language, sorry for any mistake.

[CoverUp]

Solved!!

if any one want the solution, post but i'll explain it in spanish. sorry for that

[blackdragon]

[rigomm]

Hi CoverUp

[SpoonBilly]

[CoverUp]

The problem with all of this is in the FAT library, basically in the function that is responsible for formatting the card: format(int32 mediaSize).

The problem is the following function creates a partition and then formats the card. This means adding an offset between the logical sector and the physical sector, and this offset is not scheduled later in the FAT library. Then none of functions really points to the logical address that was created when formatting.

The solution is to modify the FAT library and include the offset in all directions, however this is a pain. I do not think anyone has time for that.

My solution:
Never use the function format(), instead format the card directly from Windows when it is new.

If you already formatted using format(), format from Windows does not work, because the offset will be present, even if formatting a thousand times.

If you are in this situation (which is what happened to me) the SD card must be returned to its original state, i.e., it must delete information which was introduced in the famous format(). For this it is sufficient to write (using the library mmcsd) values in the directions 0x00 0x00 0x01 0x02 0x03 0x04 0x05 ... etc. with 0-512 being more than enough.
This translates to reset the first physical sector that contains the information of the partition table.

After you have done this, you can delete the entire contents of the SD card using WinHex and finally format it using Windows.

In this way the logical address and physical address match and both depart from the direction 0, and therefore all the FAT library functions operate.

No attached code. The only code needed is Fat.c and mmcsd.c in its original state. The steps described do not require modifying the libraries.

Greetings and enjoy the solution.

Now the English speakers will have to learn Spanish as well as we learn English: P

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El problema de todo esto esta en la libreria fat, puntualmente en la funcion que se encarga de formatear la tarjeta [ format(int32 mediaSize) ]
El problema es el siguiente, la funcion crea una particion y luego da formato a la tarjeta, esto se traduce en agregar un offset entre el sector logico y el sector fisico, como este offset no esta programado posteriormente en la libreria fat, entonces ninguna de las funciones apunta realmente a la direccion logica que se creo al momento de formatear. la solucion pasa por modificar la libreria fat e incluir el offset en todas las direcciones, sin embargo es una lata.. y no creo que nadie tenga tiempo para eso.

Mi solucion:
No usar nunca la funcion format(), formatear la tarjeta directamente desde windows cuando esta esta nueva.

Si ya formatearon usando format() formatear desde windows no sirve, por que el offset seguira estando presente, aunque formateen mil veces.
Si estan en esta situacion (que fue lo que me paso a mi) deben volver la tarjeta sd a su estado original, es decir, deben eliminar la informacion que introdujo el famoso format(), para ello basta con que escriban (utilizando la libreria mmcsd) valores 0x00 en las direcciones 0x00 0x01 0x02 0x03 0x04 0x05...etc. con un for de 0 a 512 basta y sobra.
Esto se traduce en resetear el primer sector fisico que contiene la informacion de la tabla de particiones.
Luego que han hecho esto, pueden borrar el contenido completo de la tarjeta sd usando el winhex y finalmente formatean usando windows.

De esta forma la direccion logica y la direccion fisica concuerdan y ambas parten desde la direccion 0.
y por tanto todas las funciones de la libreria fat funcionaran.

No adjunto codigo, por que el unico codigo necesario es fat.c y mmcsd.c en su estado original, los pasos que describi no requieren modificar las librerias.

Saludos y disfruten la solucion.

ahora los gringos tendran que aprender español asi como nosotros aprendemos ingles :P

[SpoonBilly]

[SpoonBilly]

But I did solved the problem of unable to read correctly from reserved sector... eventually... accidently...

I was so frustrated that at one point, using the modified mmcsd.c that I posted above, I wrote data into the reserved sectors (address 0x200 to 0x500). forgot what I wrote, but should be something like 0xFF. Then my SD card failed. It couldn't be formatted by computer, and I thought this is it, the SD card is broken...

Then, again, using the modified mmcsd.c, I wrote 0xAA into the reserved sectors (address 0x200 to 0x500). Eventually, the SD card can be formatted and it was back to life.

Since then, the problem of unable to read correctly from reserved sector is gone, the physical and logical sector offset is gone too, and the modified mmcsd.c no longer working (not sure why). I'm using the original mmcsd.c now.

Tried it with another SD card. It works. But this method is extremely dangerous. There is no guarantee that the card will be back to life. So, before someone can explain what happened, better don't try it.

[CoverUp]

I don't know why you say that SD card communicates with PIC through logical address. When you write a byte, the SD store the data pointing to the physical address. In fact, you can write data in a raw mode without any file system.
The reserved sector that you mentioned before, are present due to the partition info in the SD card.. added from format() or may be added by the manufacturer. Anyway, the partition info put the offset to the logical address 0, that Windows use to format the card. In fact all the info that must be in sector 0, are stored in the offset.
So when you delete the data present in the reserved sectors, you are deleting part of the MBR. (this is why I delete the first physical sector using mmcsd library), and this explain why your card stop to function and then work again.
If you delete the MBR the system assume that there is no format at all in the media, allowing to you to re-format the media, this time without the offset.
I recommend to use Winhex or some similar software to see the hex content of the sdcard. This help a lot in the debugging process.

[szkrep]

I'm using an old 128MB SD card. I understood, that the original format() function is buggy (it's also written in a comment in fat.c...) When I format to FAT32 with 512byte sectors in Windows, i can't do anything with the pic library. If I format it with the provided format(), pic works, but windows sees an empty card. I cleared the whole card with the methods above, in winhex the first values are 0. After that windows prompts me to format it, everything ends easily, but in the end the pic won't do anything with the card.
Does Windows 7 have any difference from xp in formatting cards? Any ideas?

[szkrep]

After a few tries it started to work correctly. The funny thing, that it's formatted with the PIC, and that was the solution. Now the computer can also read it -though the printer's SD reader blinks red, that the card is corrupted. Using a laptops internal SD reader (connected to the USB bus) everything works fine.
The "(Example: 'format 5524288' formats a 512MB card)" in the help is incorrect. That value is <desired value in MB>*2*1024 (512*1024*2=1048576; it's the half of it, and mispelled...)

[evsource]

[CoverUp]

Ok. some Updates:

Almost all SD card's manufacturers sell their products allready formated.
(With a VBR on it, ready for use)
So Logical and Physical address never match on new cards, and this library works on Physical address.

Now the quick solution is delete the MBR information of the card using this code:

[championx]

Hi! I'm trying to read and write a 4Gb SD card (SDHC). I'm using the library provided by ccs, but I can't make it work.

Is this library compatible with SDHC cards?

Thanks!

[sigma-mx]

CCS fat library supports up to 32GB
but i think mmcsd library (physical layer library) dont support SDHC command yet.