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How to use XMM memory models for SD Card + small SPI SRAM layout? - Page 2 — Parallax Forums

How to use XMM memory models for SD Card + small SPI SRAM layout?

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  • David BetzDavid Betz Posts: 14,516
    edited 2016-04-20 20:31
    Here is the C3 external memory driver.
  • matrixsmastermatrixsmaster Posts: 17
    edited 2016-04-21 00:10
    Thank you!

    Updated after investigation:
    I understood the driver's structure. If I figured out right, there's SD card partial initialization (lines 58-80) in c3_xmem. Why it's there?
    And another question: you said sd_cache isn't supported anymore, but its ported version (without cache logic, as you explained) still in the current master branch (sd_xmem.spin). Is it deprecated?
    I'm asking these questions just to make sure I can rely on some established code as a reference.
  • Thank you!

    Updated after investigation:
    I understood the driver's structure. If I figured out right, there's SD card partial initialization (lines 58-80) in c3_xmem. Why it's there?
    And another question: you said sd_cache isn't supported anymore, but its ported version (without cache logic, as you explained) still in the current master branch (sd_xmem.spin). Is it deprecated?
    I'm asking these questions just to make sure I can rely on some established code as a reference.
    I don't think the sd_xmem.spin driver works. Or, if it does, it won't work for both the SD cache and the SD filesystem. I'll have to check. Also, the C3 driver initializes the SD card because you have to put the SD card into SPI mode to avoid having it interfere with using the same SPI bus to talk to the SPI flash and SRAM chips.

  • David Betz wrote: »
    Or, if it does, it won't work for both the SD cache and the SD filesystem. I'll have to check.
    It would be great! Thank you!
    David Betz wrote: »
    Also, the C3 driver initializes the SD card because you have to put the SD card into SPI mode to avoid having it interfere with using the same SPI bus to talk to the SPI flash and SRAM chips.
    Got it. Just forgot all of them are on a single bus.
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