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USB disconnect — Parallax Forums

USB disconnect

NewzedNewzed Posts: 2,503
edited 2006-07-15 19:17 in Propeller 1
With the Demo board connected to USB and running, if you use the On/Off switch to turn the board Off, do you have to click on the "Safely Remove" icon first?· I know you have to click on that icon if you are removing the USB connection from the PC.

Sid

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2006-07-15 17:57
    The USB to serial converter is powered by the USB bus (you can see the lights flash when you plug it in - even if the board is not otherwise powered). You only have to tell the PC when you intend to unplug the USB connector.
  • cgraceycgracey Posts: 14,133
    edited 2006-07-15 18:27
    I thought this was only an issue for USB thumb drives that might need a 'write-buffer' message before going off-line. I plug and unplug FTDI-based·stuff every day with abandon and have never had any trouble. I think it's just the storage devices that have this issue. USB is meant to be 'plug-and-play', not 'Mother-may-I?'. Of course, it's likely that the PC would get this simple concept all twisted up.


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    Chip Gracey
    Parallax, Inc.

    Post Edited (Chip Gracey (Parallax)) : 7/15/2006 6:35:36 PM GMT
  • NewzedNewzed Posts: 2,503
    edited 2006-07-15 18:56
    Chip, the other day I was downloading some pictures from my digital camera and pulled the USB cable without clicking on the icon.· My PC rebooted itself and I got a screen message that it had recovered from a serious error.· I thought pulling a hot USB cable was a No-No.

    Mike, the Demo board doesn't use a converter.· It plugs straight into the USB port.

    Sid
  • Mike GreenMike Green Posts: 23,101
    edited 2006-07-15 19:17
    There's an FTDI USB UART mounted right on the demo board next to the USB connector. As far as I'm concerned, that's a USB to serial converter, just already soldered in.

    Chip, you're basically right in that the "owner" of the USB connection to a storage class device like a thumb drive is the file system of the OS and it usually wants to know if the device is about to be removed because some write buffers might not have been written to the device yet. For other devices, it depends on how they're used and who's using them (like how the driver is implemented). I've seen 'Don't Do That!!' messages from both Windows and the Mac OS when I didn't expect them for non-storage devices including serial-USB ports. Usually it's if the device has been opened by some program and not yet closed. On the other hand, I've often pulled non-storage USB devices with nary a peep. The Mac seems to be better behaved than Windows in this regard, but "your mileage may vary". It probably has to do with who wrote the driver and how well they did it.
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