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Exp board, wont run w/o usb? — Parallax Forums

Exp board, wont run w/o usb?

TJHJTJHJ Posts: 243
edited 2008-03-19 15:41 in Propeller 1
So If I dont have my usb plugged into the board, it turns on for about a second and then resets?
Any Ideas why?
Works find once its got the usb cable plugged into it. after a power reset.

Thanks
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Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-03-18 22:01
    There's a known problem with the PropPlug/PropClip when it's left attached to a Prop device without the USB present or powered.
    Intermittently, you can get spurteous resets with power coming from the transmit (to the PC) line on the Propeller. The solution is to disconnect it or to add additional loading to the DTR and receive (from the PC) line. Something as simple as a 1K resistor to ground will help.
  • joeldjoeld Posts: 49
    edited 2008-03-19 03:53
    Did you happen to be using full duplex serial or some similar method to talk back through the usb port to a debug terminal such as hyperterminal? I found that leaving a serial connection to the usb port running in a cog with the usb disconnected caused problems similar to what you describe.
  • TJHJTJHJ Posts: 243
    edited 2008-03-19 15:17
    I kinda spoke wrong, Im sorry. I meant demo board.
    But its dead now... So I guess it was just on its way out.

    Thanks anyway.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-03-19 15:41
    Here is another thread that deals with the same issue. Putting a 1K pullup on A30 has been a successful workaround for some users. It's not a pretty solution, since it keeps the FTDI chip in the Prop Plug powered through an I/O pin. But that's what prevents the errant resets. Hopefully, Parallax will change the Prop Plug design to include an LVC-type I/O buffer on RX and TX before they have any more of them made, which would solve the problem once and for all.

    -Phil
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