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I'm using an Attiny85 to interact with a computer using an USB connection, and everything works fine except when I restart my computer and the Attiny85 is connected. When Windows end to boot up the Attiny85 isnt't recognized, and on Device Manager it's listed like this:

Unknown USB Device (Device Descriptor Request Failed)

If I unplug the Attiny85 and then plug it back in, everything works just fine.

Is there any to make it detectable at boot time without having to always unplug/plug it?

EDIT:

More details:

I'm using this board ATtiny85 USB Mini Dev Board

and libusb-win32 as the USB driver

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    The ATTiny doesn't really do USB. Making it interface with a USB port using something like V-USB is a hack at best. You shouldn't expect it to work properly in all respects.
    – Tom Carpenter
    Commented May 6, 2017 at 10:49
  • You could use an oscilloscope and/or a USB protocol analyzer to find out what exactly V-USB does wrong, but in any case such a hacky software emulation cannot be fixed. Better use a microcontroller that actually supports USB (e.g., a Teensy).
    – CL.
    Commented May 6, 2017 at 10:54
  • Added more details (board and USB driver) to help in problem analyis
    – Gonçalo Cardoso
    Commented May 6, 2017 at 11:53

1 Answer 1

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I don't have enough reputations to make a comment so I will drop my 2 cents here.

There should be more elegant way to do this but as a fast solution I would recommend two things:

  1. If it is possible, add a push button to your board to reset the MCU manually when the PC is booted up.

  2. You can make a software reset after powering up the board by a certain time (e.g. 10 sec) by using watchdog timer.

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  • I can't use the button idea because the board will be inside a case, and it wouldn't be practical. The idea about the watchdog timer won't work because the board is always connected, so when the PC is off I would be executing the reset procedure at every 10 seconds, and I don't know if it would "like it".
    – Gonçalo Cardoso
    Commented May 7, 2017 at 17:43
  • @GonçaloCardoso Regarding watchdog timer, you can use watchdog timer just one time. You can handle this in your code.
    – Macit
    Commented May 7, 2017 at 18:10
  • But at what time would that be?
    – Gonçalo Cardoso
    Commented May 7, 2017 at 18:20
  • @GonçaloCardoso The time completely depends on your application. To perform a software reset one time look at this link.
    – Macit
    Commented May 7, 2017 at 18:42
  • The problem is that I need to make the restart when Windows boots up, and I haven't managed to find a way for the board to detect it.
    – Gonçalo Cardoso
    Commented May 7, 2017 at 19:23

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