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Topic: Cheap small capacity SD Cards? (Read 1 time) previous topic - next topic

bratan


The protocol used on SDHC is different not backwards compatible.

I'm having nightmares that soon they'll only stop making non-SDHC cards  :smiley-roll-sweat:
Anyway after digging online, I found decent deal on eBay for lot of used 256Mb microSD cards ($.99 plus shipping), and $.99 adapters. Totally comes up around $2.25 per unit (card+adapter+shipping), not too bad I guess...
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SirNickity


The protocol used on SDHC is different not backwards compatible.


Ehh... in all our cases, we're using the SPI fallback protocol anyway.  That is a non-optional part of the SD spec.  The only thing that differs is the initialization sequence and how blocks are addressed.  It would be foolish to implement a design that didn't interrogate the card to ensure the right method was used, so I don't see backwards compatibility suffering any time soon.

If I'm wrong, I'd love to hear the opposing viewpoint.

bratan



The protocol used on SDHC is different not backwards compatible.


Ehh... in all our cases, we're using the SPI fallback protocol anyway.  That is a non-optional part of the SD spec.  The only thing that differs is the initialization sequence and how blocks are addressed.  It would be foolish to implement a design that didn't interrogate the card to ensure the right method was used, so I don't see backwards compatibility suffering any time soon.

If I'm wrong, I'd love to hear the opposing viewpoint.

It looks like you are right, I had no idea it's backwards compatible. Indeed latest WaveHC library for example does support SDHC cards! :)
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smeezekitty

Then why do SDHC cards behave erratically in very old devices?
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

SirNickity

Maybe it doesn't comply with the recommended interrogation sequence?  There's a flowchart in the SD specs showing you how to properly differentiate.  It's backward compatible.  If you (as a designer) just initialize and go, instead of probing and verifying behavior, you may end up using the wrong command set.  Just a guess.

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