SD Card Initialization problem

[andreluizeng]

Hi,

I have two boards to work with sd/mmc card with different pics, board 1 has 18f2620 and board 2 18f4620, both running at 10Mhz (or even 40Mhz pll) with 3.3V. Also I have 3 sd cards: nokia micro sd 256mb, sandisk micro sd 2GB and Kingston SD 2GB.

In board 1 (with 18f2620) I've tested these sd cards and I had success in all three.

but in Board 2 (18f4620) only the micro sds worked. Kingston 2GB doesn't work at all. And in a deeper analysis I found out that Kingston sd card never leaves idle state, and the worst thing is... after sending cmd0 and then cmd1 (cmd55+acmd41) the sd cards respond with 0x01 (idle state) two or three times then the sd card just respond with 0xff. Somebody just experienced this problem too ? What could be causing that? bad pcb layout or sd connector ?

Hope someone can help.

thanks in advance.

Andre
_________________
Andre

[asmallri]

[andreluizeng]

asmallri

dont worry about 40MHz, Im using only 10MHz... a part of my schematic can be viewed in this link:

http://img211.imageshack.us/img211/8601/board1.jpg


this is for board 1 with pic18f2620 the difference from another board is that I have some dipswitches between PIC´s pin and the peripherel connected on it.

I just got more 4 cards to test following by:

Vendor Type Size Result

1 - Lexar professional SD Card 1GB Success
2 - Cannon SD Card 32MB Success
3 - Sandisk MMC Card 32MB Success
4 - Kingston Micro SD 2GB Failure


I dont understand.. Im just having problems with Kingston cards =(

and the result was the same.. after a few answers (0x01) after CMD1 (or CMD55 + ACMD4) the card stop responding (0xff).

thanks in advance.

regards.
_________________
Andre

[ckielstra]

You are switching the power to the SD card by a transistor. The minimum allowed voltage for these cards is 2.7V.
3.3V - Vce voltage of 0.6V = 2.7V

In theory this should be OK, but you have no error margin. It is a simple test to replace the transistor by a jumper.

Are you using the code as posted in http://www.ccsinfo.com/forum/viewtopic.php?t=37463 ?
Read my comments in that thread.

[andreluizeng]

ckielstra

I measured 3.28V on SD card... after that Im sure that the supply voltage is not the problem.


thanks

regards.
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Andre

[andreluizeng]

ckielstra

I made a little modification in this code.. the way that Im sending commands and treating the responses... but In both cases I´ve got the same problem with Kingston Cards.


regards.
_________________
Andre

[ckielstra]

[asmallri]

I suspect your power supply switching logic is the culprit. The circuit is too close to the tolerances - its operation is dependant on HFE of the transistor. To test this theory, short out the emitter-collector.

Logically you would expect the current consumption to be higher on the higher capacity cards however the age of the respective implementation means we cannot assume that is the case.

I have tested Kingston cards without problem and if you are 100% sure your 2620 implementation works, then I would be examining the hardware implementation in greater detail.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[andreluizeng]

Ok, I will make these modifications and see what will happen.

thanks again, you are helping me a lot, I will post results as soon as I can


regards.
_________________
Andre

[andreluizeng]

You were right guys... the problem was in my switching logic... kingston was not hanging out on the edge, when I made the jumper on transistor and it worked. Now Ill try to fix it in a better way is possible, since this circuit is already mounted in a pcb.

thanks again for helping.

regards.
_________________
Andre

[asmallri]

Try a 1K base resistor instead of 2.2K
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[Guest]

asmallri

it worked with 1k5, thanks a lot.

now im going to bed and try to sleep a little, 2:22 am here, and I need to wake up early to go to work... what im doing here is just for fun =)

best regards.