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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

Alya
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    You want to have two devices talking to the same SD card? At the same time? You can't. – Majenko Aug 01 '21 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 Aug 01 '21 at 15:35
  • if one after another can be avoided with one device telling the other to write for it, it might simplify things. – Abel Aug 01 '21 at 17:18
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    Could you please explain your idea clearly.. – Alya Aug 01 '21 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 Aug 02 '21 at 04:18
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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 Aug 02 '21 at 07:22
  • Think of it like a network. You have one USB hard drive, but two computers. You plug the hard drive in to one computer and share the filesystem across the network to the other computer. You don't plug the hard drive into both computers. That is what you need to do with your SD card. You connect it to one MCU then "share" it with the other one through some other communication medium (network, serial, I2C, whatever is most suitable for your usage). – Majenko Aug 02 '21 at 10:10
  • That’s what we exactly thinking about and what led us to the idea of using a level converter or shifter, the level converter has Tx and Rx pins , through these pins we’re planning to take data from the Arduino zero and send them to the Uno using the Rx, what do you think about the idea? – Alya Aug 02 '21 at 12:57
  • The level converter we currently planning to use is sparkfun 2 Channel 5V 3.3V I2C TTL Logic Level Converter Module – Alya Aug 02 '21 at 13:06
  • https://www.fruugo.eg/2-channel-5v-33v-i2c-ttl-logic-level-converter-module/p-52178967-105041923?language=en&ac=google&gclid=CjwKCAjwr56IBhAvEiwA1fuqGhTPCLet8h74pZrUWV_CKpYDl20vlOBIhPEua3GKtN1ljVWm-dfoZxoCtisQAvD_BwE – Alya Aug 02 '21 at 13:13

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