Shop OBEX P1 Docs P2 Docs Learn Events
Project only works when PropPlug in-situ — Parallax Forums

Project only works when PropPlug in-situ

HughHugh Posts: 362
edited 2012-01-11 12:47 in Propeller 1
This has me stumped.

I have a project on a protoboard. It only runs if the PropPlug is connected (to the protoboard and the PC). If it is not present the SD card fails to mount.

Any code writing to the EEPROM has been removed.
The reset button on the protoboard doesn't have the same effect as the PropPlug being in place.
There are no connections to pins 28 - 31.

I can only assume that the PropPlug is pinning down some floating voltage somewhere.

Any thoughts?

Thanks
Hugh

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-01-10 05:58
    Have you tested it with the Prop Plug completely removed?

    If you have debug statements sent to the PC with a Prop Plug in place it will reset the Prop.

    Do you have any debug statements?

    I'd suggest posting the code so others can check it.
  • HughHugh Posts: 362
    edited 2012-01-10 06:29
    If either the RX or TX pins of the propPlug are connected when the protoboard powers up it all works OK; if not, it won't mount the SD.
  • HughHugh Posts: 362
    edited 2012-01-10 06:30
    Duane Degn wrote: »
    Have you tested it with the Prop Plug completely removed?

    If you have debug statements sent to the PC with a Prop Plug in place it will reset the Prop.

    Do you have any debug statements?

    I'd suggest posting the code so others can check it.

    Nope. None at all.

    The code is spectacularly poor! :innocent:
  • Mike GreenMike Green Posts: 23,101
    edited 2012-01-10 07:40
    There is a known problem with most of the USB to serial interfaces used where, when there's no PC connected, the TX (or RX) lines can provide enough power to the interface chip to cause it to partly function ... enough to reset the Propeller. That's why everyone is asking about debug statements. Those initialize the TX and RX I/O pins which can supply this power. Once the Propeller finishes its reset sequence, the TX and RX pins are set to input mode and can't supply power. If your program changes that to set up for debugging, it can cause a reset. The simplest solution for this is to never use I/O pins 30 and 31 unless you have a PC connected.
  • RaymanRayman Posts: 14,849
    edited 2012-01-10 09:27
    This sounds like a wiring problem to me. Something must be wrong with the power supply wiring somewhere...

    If you have a voltmeter, try measuring Vdd everywhere and make sure all the ground connections are good...
  • RaymanRayman Posts: 14,849
    edited 2012-01-10 10:34
    BTW: There was a recent post where somebody had an SD card hooked up with long wires and it needed a capacitor to make it work.
    Anyway, you might try adding a ~10 uF tantalum capacitor between Vdd and Gnd near the SD card...
  • HughHugh Posts: 362
    edited 2012-01-11 12:05
    Its a design and installation issue - when I opened the box, the presence of my fingers in the vague area changed the way it functioned. It might be my electric personality, but I suspect (my) poor design and wiring.

    Prop-based Theramin, here I come!
  • Mike GreenMike Green Posts: 23,101
    edited 2012-01-11 12:47
    Propeller input pins, like most CMOS input pins, are high impedance and are very sensitive to electric fields like from stray fingers. It helps to use pullup or pulldown resistors, particularly with switch contacts or other digital devices that sometimes are in a high impedance state as well.
Sign In or Register to comment.