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Propeller Reboot Issue with Propeller Plug — Parallax Forums

Propeller Reboot Issue with Propeller Plug

I've got a design that I would like to leave the Propeller Plug plugged in all the time and just unplug the computer from the USB port. The issue I'm having is when there's
no computer plugged into the Propeller plug. The prop reboots constantly when its starts the Parallax Serial Terminal object. If I disconnect the propeller plug from the prop everything works fine.

Ive attached my code and picture of the board.
Do the demo boards that parallax make have this problem?

Comments

  • The Prop resets when the RST line goes low. On the Prop Plug, when it is not plugged into a computer, there is now way for it to get the power to pull the RST line high, so it falls to the low state. You can try putting a 10k pullup resistor on the RST line to prevent this. The Prop Plug should be able to pull the line low even with the 10k pulling it up.

    If the Prop Plug starts having issues pulling RST low, you could then try increasing the resistor value.

  • Tried that it didn't work. Looks like the Prop Plug REV E has some schematic changes in it. I have like the very first one from 2009. I might try ordering the new one.

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,001
    edited 2021-06-04 20:40

    This is a well-known issue with the Prop Plug. It stems from the fact that the plug is parasitically powered from the Prop's TX line when there's no PC attached. When the line is brought high by starting a serial object, the FTDI chip powers up and pulls RST low, ad infinitem. One cure -- not a great one -- is to add a pull-up resistor to TX so that the FTDI chip is always powered, killing the cycle of resets.

    -Phil

  • msrobotsmsrobots Posts: 3,365

    another trick would be a switch or jumper between /RST and the ProPlug /RST, call it Programming enabled or not.

    Disconnected no resets and no programming.

    Enjoy!

    Mike

  • Run it bare bone,s no buck converter or servos attached, see if it resets. power the prop with its own supply, no buck converter attached, what servo are you running, are they the GM cluster servos

  • @"Phil Pilgrim (PhiPi)" said:
    This is a well-known issue with the Prop Plug. It stems from the fact that the plug is parasitically powered from the Prop's TX line when there's no PC attached. When the line is brought high by starting a serial object, the FTDI chip powers up and pulls RST low, ad infinitem. One cure -- not a great one -- is to add a pull-up resistor to TX so that the FTDI chip is always powered, killing the cycle of resets.

    -Phil

    The latest PropPlug design removes the parasitic powering "feature". If that was the OP issue, a new PropPlug would solve.

  • AwesomeCronkAwesomeCronk Posts: 1,046
    edited 2021-06-05 18:38

    Well that’s good to know about the Prop Plug. I should probably go ahead and get one of the newer ones soon, have sorta been looking to do so for a while.

  • GenetixGenetix Posts: 1,521

    VonSzarvas,

    Can existing Prop Plugs be modified to disable Parasitic power?

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