we are currently working on a device that needs us to connect an sd card reader to 2 Arduino’s ( Uno and zero) , however, we just found that it is not possible to do so without a level converter , may we have some help about how to do the proper connection from the sd ( that is already connected to arduino zero) to the level converter and then to the Uno. We want to make sure that both microcontrollers work at the same voltage of 3.3V. The Arduino Uno works at 5V whereas the Zero works at 3.3V which is why we need the level converter

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    You want to have two devices talking to the same SD card? At the same time? You can't.
    – Majenko
    Commented Aug 1, 2021 at 13:05
  • Actually they have to talk to the sd card one after another, one should get the data first and then the other one should transfer it.
    – Alya
    Commented Aug 1, 2021 at 15:35
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    Could you please explain your idea clearly..
    – Alya
    Commented Aug 1, 2021 at 17:56
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    A circuit diagram and a better description of the objective would help in providing answers. It sounds like you have one MCU with an SD card, and a second one without. You want to connect the second MCU and have them both access the SD card? I suggest splitting up all the work and designing a modular approach to who is doing what. In hardware I’ve found devices like Pololu 2595 Logic level shifters useful and easy to connect. I suggest avoiding attempting to have two devices sequentially writing directly to one SD card, rather having one MCU coordinate the SD I/O for all of them.
    – RowanP
    Commented Aug 2, 2021 at 4:18
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    Two devices writing to one SD card like they have exclusive access, without very strict arbitration to control which device is writing or reading which part of the card, will corrupt the file system on the card very quickly. It’s much simpler and safer to have one “master” like @RowanP suggested.
    – StarCat
    Commented Aug 2, 2021 at 7:22


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