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nrf51 (spim) <-> sd card

Stanislav Silnitskiy

Hello! Do I need any extra passives, connecting SD card to SPIM of nRF51? It works fine with MOSI, MISO, SCK, SEL, VCC and GND directly connected, just want to be sure it will not surprise me one day.

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  • 0

    From reading various sources on the internet it seems that you should use pull-up resistors on all logic lines, or else some SD cards may not work. This is because the lines are floating when the SD card is not inserted or when the nRF chip boots up. Using pull-up on all pins seems to be a part of the SD card spec (have not confirmed this).

    Adding pull-up resistors in the layout will not do any harm since you can choose to leave them unconnected. They will take up space however.

  • 0 in reply to Ole Bauck

    "then some time pins are floating". That can cause problems, putting the SD card in some state. I have not experienced this myself, but searding on "SD SPI pull up" on the internet gave a lot of discussion on whether or not pull up was necessary. You will probably get away with no external pull up resistors.

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  • 0 in reply to Ole Bauck

    "then some time pins are floating". That can cause problems, putting the SD card in some state. I have not experienced this myself, but searding on "SD SPI pull up" on the internet gave a lot of discussion on whether or not pull up was necessary. You will probably get away with no external pull up resistors.

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