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SPI multi-master

paddu1
Expert 1195 points

hi,

We want to have 2 AM335x devices connected to the same SD Card,
both to read and write to the card.

Whenever one(Device 1) is reading or writing to the card, the other(Device 2) will be in reset state
so there will only be one master in line at a time.
After finishing the read/write operation from Device 1, it releases the Device 2 from
reset and Device 2 also does the same operation.

The problem is both the Device 1 and Device 2's SPI signals interfere and the signals
don't go Low.

Does anybody tried SPI multi-master, please let me know if there is any suggestions.

Regards.
Paddu

  • 0
    TI__Guru 64490 points

    What specific signals are you using in this scenario?

    Do you have existing target boards with this architecture, or are you experimenting with Evaluation Kits?

    If you are controlling the reset of Device 2 (ie. porz), then you should look at the reset state of the appropriate signals from the Ball Characteristics table 2-7 in the datasheet.  If the signals are held in a hi-impedence state, you are probably in good shape, but if the signals are held in a active state, then there would be conflict.

    I have not implemented this type of structure so my comments are more specific to the electrical aspects, not protocol.

     

  • 0 in reply to BrandonAzbell
    Expert 1195 points

    Thank you..

    According to the datasheet all the SPI signals will be in High impedance during reset state.

    We were able to solve the problem, the device was not actually in the reset state.

    We appreciate your kind support.

    Regards

    paddu.