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3 wire data only USB

SIMON LATOUR
Prodigy 245 points

Hello All,

We have a special application that may require to do 3 wire data-only usb. ( No 5v line)  Assuming the DSP is implemented as a peripheral and is self powered, do you think it would be possible to do this with the DSP ?

Any of you ever tried it ?

Thanks.

p.s.:  I know it is not standard and not in line with the USB specifications so please do not reply just to tell me this. 

  • 0
    TI__Guru* 84110 points

    Simon,

    It is pretty hard to guess an answer here since you have not told us which device you are using. The answer may be the same for all of them, but there could be driver differences or hardware differences that have to be considered.

    In general, you will have to make the USB pins behave like standard USB pins. You will have to provide power wherever it needs to be so that the peripheral thinks it is being supplied power correctly. And you will have to study the spec to make sure any power-applied or power-removed time regions, if they exist, are handled according to the spec so you can be confident in the drivers' behavior.

    Any debug of and modifications to the driver code will be yours to do, of course.

    It seems reasonable to me that this can be done, but I have not tried it.

    Regards,
    RandyP

  • 0 in reply to RandyP
    Prodigy 245 points

    Thank you Randy for you answer.

    In this case, I ( the dsp) am the peripheral.  I tested it rapidly by simply cutting the 5v wire in a usb cable and it is working.  So yes is is doable if the dsp is the peripheral at lease !