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SD Card failiers — Parallax Forums

SD Card failiers

BigFootBigFoot Posts: 259
edited 2011-02-23 17:54 in Propeller 1
Have any of you guys had problems with SD Card failures in the field ?

We are using the FSRW Femto drivers and more or less the same circuit
that is on the Parallax Dev boards. We have seen three of the SanDisk 2 GB
cards fail and one of the Kingston cards become readable in the PC but not
in out PoS terminal.

Our circuit is enclosed.
pdf
pdf
Polr74Sd.pdf
23K

Comments

  • localrogerlocalroger Posts: 3,452
    edited 2011-02-22 17:22
    Where did you get your cards? Counterfeit SD cards made with failed-the-test flash are a known problem on some of the cheaper supply channels. Both SanDisk and Kingston fakes have been spotted in the wild.

    I have about ten SD cards, which I use heavily both in props and with SD/USB adapters, and I haven't had a failure yet. But I got them all from domestic retailers like Office Depot, generally on sale but not as cheap as some of the sketchier online sources.
  • MacTuxLinMacTuxLin Posts: 821
    edited 2011-02-22 17:30
    Seen some of those flaky cards myself too.

    And, you might want to try adding another 1uF to your bypass as the writing might consume >100+ mA.
  • RaymanRayman Posts: 14,886
    edited 2011-02-22 18:41
    Make sure your using lastest FSRW (2.6 I think). And, make sure it's using the "safe_spi" sub object.
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-02-22 23:42
    You should have a better cap across the power on the SD socket. I cannot recall the recommended size. I have a 10uF tantalum on my pcbs.
  • BigFootBigFoot Posts: 259
    edited 2011-02-23 07:39
    Thanks for all the ideas, phony cards are a real possibility. There is a 47uF high quality
    tantalum cap very close to the SD card socket on the board. Do you think that is enough ?
    It is also the bulk storage for the processor.
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-02-23 14:43
    It depends on how close it is to both the prop and the sd card, and also what else you have on the pcb. I have 3x 10uF tantalums on my RamBlade. 1 for the card, 1 for the prop and 1 for the sd card. I learnt many moons ago that you need proper decoupling to ensure problem free operation. And our chips have not only got a lot faster, they also power down between operations. This causes a great load on the bulk capacitors that normal 0.1uF and 0.01uF just simply do not provide. You also need to use high quality X7R ceramic capacitors these days for bypassing.
  • UnknownUnknown
    edited 2011-02-23 14:47
    I know some programmers who feel that you can write to a card 5,000 times and not the hype put together by marketers.

    I think that someone should do some real but independent testing.
  • MacTuxLinMacTuxLin Posts: 821
    edited 2011-02-23 17:54
    Just another thought since your's is a commercial project. Did you provide backup power supply while the data are in the mist of being written to the SD when the main power is either switched off or sudden power outage? RC maybe?
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