I have the problem solved.  I realize I left out an important point in that
I'm running my PIC at 5V to connect to a 3.3V powered SD card.  I used
voltage dividers to drive signals into the card and pulled up unused inputs
of the SD card with 47K resistors to 3.3V.  Since the data sheet for the PI=
C
said the SDI input is a Schmidt trigger I figured 3.3V would not be seen as
a logic 1 since the data sheet said it needed something like 0.9Vdd.  So, I
put a 914 signal diode in series with a pull up to 5V on the PIC side.  Thi=
s
works great for old SD cards but not for new.

It turns out that when I measured the voltage on the SD card side when the
SD card was not driving the output, it was 4.3V.  Shame on me.

I disconnected the input to the PIC and put my logic probe on the SD side
and saw that it was responding to repeated CMD0s.  So, I just wired the SD
data out to the PIC data in and I was able to get the SDHC card out of the
idle state and read control registers.

I guess newer cards get a bit angry about the over voltage on DO and refuse
to play.=20

I just wanted to say thanks and pass along another secret about SD card
interfacing and to say sorry for the bother.

   Ted.





trossin wrote:
>=20
> Thanks Joe,
>=20
> It looks like you do the same thing I do except for the 100us delay after
> asserting CS.  Add added that wait to my code but still no luck going int=
o
> SPI mode.  I also gave it a try with a 2 GB Lexar 60x standard capacity
> (SD) card and it behaved the same way as the Pny 4G SDHC (class 4).  It
> did not respond to CMD0 with CS asserted via the SPI DO pin.  I left it
> retrying in an infinte loop and it just never responded.   My 512 MB
> Sandisk SD and 16 MB Canon MMC cards respond right away to CMD0 and I'm
> able to get out of the idle state and read the boot block.
>=20
> I have 47K pull up resistors on all the inputs just like all the examples
> on the web.  I've looked at 5 or 6 different code segments as well but I'=
m
> not seeing anything special.  I will say that everyone does the init
> sequence a little differently.
>=20
>    Ted.
> =20
>=20
> ivp wrote:
>>=20
>>> Any suggestions would be great
>>=20
>> Ted, here's the initialisation sequence I'm using with a dsPIC and
>> 4GB and 8GB SDHC cards, both standard and micro
>>=20
>> My experience with various makes of cards so far has made me
>> wary of some substitution problems, so it's a work in progress,
>> but initialisation seems reliable
>>=20
>> Joe
>>=20
>> ...
>> --=20
>> http://www.piclist.com PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>>=20
>>=20
>=20
>=20

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