On Tue, Nov 8, 2011 at 10:50 AM, IVP <joecolquitt@clear.net.nz> wrote:
>> Unless you are booting an os or equivalent structure from the card,
>> boot sector is not necessary
>
> Yes, I have a couple of uses where the dsPIC's is the only s/w
> involved and I don't have to make the data FAT compatible (ie the
> card is just a big dumb block of memory and I can write anywhere).
> However, I'm working on applications where card files will be written
> by a PC so I had to know how to find them

Food for thought ; you don't need to partition the card to write/read
from, you can bulk write/read as long as the device is recognized by
the os (not the filesystem). A filesystem is not necessary but it
surely will make things simpler.

>
>> I use a tool for these kinds of stuff "dd"
>
> Me too, after it was recommended here not so long ago. AFAIK it
> doesn't have a GUI, just Command prompt
>
> I'm using frhed to view file generated by dd. Together they are very
> helpful for testing s/w and diagnosing problems. It's how I found that
> the Boot Sector wasn't where I expected it

dd lacks gui but it's so straightforward that I doubt you will need
one.It's output will be written to a file and file can be viewed with
vi, pico, kwrite, notepad, frhed and so on.  I live in bash usually
thus it's easy to do any kind of manipulation for directing
input/output of dd.
>
>> u can force the format to put the Boot Sector at 0x000000 but that
>>wouldn't be a bootable disk unless it contains the necessary flags
>
> I've got the other two cards to refer to for how a Boot Sector at 0x0
> is put together if I need to. Now that I understand that these cards have
> a partition it's simple enough to work with that
>

Each SSD card  I have played with allowed multi partition on it even
the old MMC ones. I remember I got ext3, reiserfs and jfs on the same
card.

>
> --------------------------------------
>
> I've written the below, but not tried it yet. The numbers check out
> for the first directory sector at byte 0xBAE000
>
> Boot Sector at 0x2000 * 0x200 =3D byte 0x40000
> numfat =3D 0x2, fatsz32 =3D 0x1EA7, resvdsec =3D 0x22
>
> (0x400000 + 0x200*((2*1EA7 + 22))) =3D 0xBAE000
>
> =A0read_fat: =A0clr =A0 =A0 sec_adr_lo =A0 =A0 =A0 =A0 =A0 =A0 =A0;sector=
 0
> =A0 =A0 =A0 =A0 =A0 clr =A0 =A0 sec_adr_hi
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 #ram2,w8
> =A0 =A0 =A0 =A0 =A0 call =A0 =A0getsector =A0 =A0 =A0 =A0 =A0 =A0 =A0 ;re=
ad 512 bytes, store data at
> ram2
>
> ;find Boot Sector / Root Directory
>
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 ram2,w0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ;=
read first byte of sector
> =A0 =A0 =A0 =A0 =A0 bra =A0 =A0 z,partition =A0 =A0 =A0 =A0 =A0 =A0 ;if 0=
, then Boot Sector is not at
> 0x0
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 ;else E9 or EB
> boot: =A0 =A0 =A0mov =A0 =A0 ram2+numfat,w0 =A0 =A0 =A0 =A0 =A0;BPB_NumFA=
Ts
> =A0 =A0 =A0 =A0 =A0 mul =A0 =A0 ram2+fatsz32 =A0 =A0 =A0 =A0 =A0 =A0;*BPB=
_FATSz32
>
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 ram2+resvdsec,w0
> =A0 =A0 =A0 =A0 =A0 add =A0 =A0 w0,w2,w0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0;=
+BPB_ResvdSecCnt
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 w0,dir_sector =A0 =A0 =A0 =A0 =A0 ;start =
sector of directory
> =A0 =A0 =A0 =A0 =A0 add =A0 =A0 w0,#8,w1
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 w1,offset =A0 =A0 =A0 =A0 =A0 =A0 =A0 ;of=
fset to next cluster
>
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 w0,sec_adr_lo =A0 =A0 =A0 =A0 =A0 ;fetch =
non-00 directory sectors
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 #dir_ram,w8
> =A0 =A0 =A0 =A0 =A0 call =A0 =A0getsector =A0 =A0 =A0 =A0 =A0 =A0 =A0 ;st=
ore at dir_ram
> dir_loop: =A0inc =A0 =A0 sec_adr_lo
> =A0 =A0 =A0 =A0 =A0 skpnz
> =A0 =A0 =A0 =A0 =A0 inc =A0 =A0 sec_adr_hi
> =A0 =A0 =A0 =A0 =A0 call =A0 =A0getsector
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 temp0,w0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0;=
test first byte of sector
> =A0 =A0 =A0 =A0 =A0 bra =A0 =A0 nz,dir_loop
>
> =A0 =A0 =A0 =A0 =A0 return
>
> ;if nothing at sector 0 then look for Boot Sector
>
> partition: mov =A0 =A0 #1,w0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ;Boot Se=
ctor address at 0x1be + 8
> (0x1c6)
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 w0,sec_adr_lo
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 #ram2,w8
> =A0 =A0 =A0 =A0 =A0 call =A0 =A0getsector
>
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 ram2+#0xc6,w0 =A0 =A0 =A0 =A0 =A0 ;fetch =
0x1c6 and 0x1c7, LSW
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 w0,sec_adr_lo
>
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 ram2+#0xc8,w0 =A0 =A0 =A0 =A0 =A0 ;fetch =
0x1c8 and 0x1c9, MSW
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 w0,sec_adr_hi
>
> =A0 =A0 =A0 =A0 =A0 mov =A0 =A0 #ram2,w8 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0;=
get Boot Sector
> =A0 =A0 =A0 =A0 =A0 call =A0 =A0getsector
>
> =A0 =A0 =A0 =A0 =A0 bra =A0 =A0 boot =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0;examine
>

Your code will check if 0xBAE000 is occupied or not, give it a try.

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