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Thread: Teensy 4.1 possible to hook up sdram?

  1. #1
    Junior Member
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    Teensy 4.1 possible to hook up sdram?

    Hi,

    I've checked in the datasheet of the 1060 that it has an external memory interface for sdram. So I'm thinking and research how hard it would be to hook up some sdram (around 64MB) to the teensy or if it isn't possible at all.

    There is this other board called daisy with an stm m7 64mb sdram an dac on board. So I was wondering if something like this could be achieved with the teensy.

    Kind regards

    Biwog

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Not possible. Many of the required signals are not accessible.

    But you can add QSPI PSRAM.

    https://www.pjrc.com/store/psram.html

    The raw performance for cache misses is obviously lower for 4 bit QSPI compared to 8 or 16 bit SDRAM. But for many common uses where the 32K cache helps, the speed can be pretty good.

  3. #3
    Senior Member+ Frank B's Avatar
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    I'm afraid currently there is no good solution for more than 16MB RAM.
    One could come up with the idea of simply using multiple (more than 2) PSRAMs on QSPI. But that's difficult because they would need multiple chipselect lines - and even if you do that, the very useful cache would get into trouble. You would have to disable it. That would be very negative for the performance.

    However, if you don't need it to be superfast, and do not need the cache, you can just add a few chips to SPI.
    Last edited by Frank B; 01-18-2021 at 02:28 PM.

  4. #4
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    Quote Originally Posted by PaulStoffregen View Post
    Not possible. Many of the required signals are not accessible.

    But you can add QSPI PSRAM.

    https://www.pjrc.com/store/psram.html

    The raw performance for cache misses is obviously lower for 4 bit QSPI compared to 8 or 16 bit SDRAM. But for many common uses where the 32K cache helps, the speed can be pretty good.
    Ok, Thanks. Will this change on a future Teensy version?

  5. #5
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    SDRAM needs about 26 pins to connect to it, several control lines and an 8-bit databus and 12 or so address bits.

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