Multiple Device SD Card Sharing

Discussion in 'The Projects Forum' started by Riegerb, Nov 24, 2012.

  1. Riegerb

    Thread Starter New Member

    Nov 24, 2012
    Hey Guys!

    I'm working on a project that requires both an Atmel2560 and a connected computer to both have the capability to read/write to an SD card. Basically, the Atmel2560 is connected to the MicroSD on board the PCB through a Hex Converter. The board is designed to operate with connection (and power) to a USB-B port. The Atmel will be dumping data to the SD card continuously however from time to time we need the ability for the computer to explore the SD card and access the data. If that requires pausing the read / write from the Atmel - we can live with it.

    I've been looking into solutions involving the LUFA code using an Atmega32U4 or possibly the VUB300. However, no clear solution is presenting itself.

    Your help / suggestions are greatly appreciated! I'm happy to provide any additional details that are needed.

  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    I've done something similar using Microchip PICs a few times. Microchip provides sample application programs to make a micro work as the middle man for an SD card reader, so to the PC it looks like a SD card reader. That's one end.

    On top of this I graft on the Microchip MSD (Mass Storage Device) library that adds a FAT32 file system. My app does whatever it needs to do, while periodically calling the USB update code. AFAIK calling this 10 or more times a second is sufficient.

    Thus both the PC and the PIC can both access the card, though I doubt they can do so at the same time. For the uses I had (mostly a SD card bootloader) they do not need to access the card at the same time so there was never a question of corrupting the state f the SD card (does it have one? I believe it must).

    That's a direction to look. Sorry I have zero familiarity with Atmel devices and support to suggest anything more specific.