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BOE without a tail? — Parallax Forums

BOE without a tail?

RacerXRacerX Posts: 6
edited 2006-06-24 18:33 in General Discussion
I have a small project running on a BOE.· Must be an older BOE as it doesn't have the power switch on it or the servo connectors.

It works fine as long as the serial cable from the computer is plugged in.· If I try to operate without the serial cable plugged in, it goes all wacky on me.

Will the BOE operate without being tethered to the computer?

·

Comments

  • Russ FergusonRuss Ferguson Posts: 206
    edited 2006-06-20 01:44
    The BOE WILL operate without the serial cable being connected.

    What does "all wacky" translate into?
  • RacerXRacerX Posts: 6
    edited 2006-06-20 02:53
    I am reading 8 pushbutton switches using 1K resistors on pin 0 (like the app note in the stamp manual) with the RCtime command.

    HIGH RC ' charge the cap
    PAUSE 10 ' for 10 ms
    RCTIME RC, 1, result ' measure RC discharge time
    IF result<460 THEN GOSUB button_press

    when the serial cable is connected this works fine. But when I disconnect the cable, my button reading routine continuously returns a value less than 460 but higher than 430. Which kicks it into the subroutine for button #8. I suppose I may be able to fine tune the numbers I am using to interpret the switch press, but I am unsure why its happening at all. When I tested my switch values, the lowest number I got when no button was pressed was 518.
  • Bruce BatesBruce Bates Posts: 3,045
    edited 2006-06-20 06:21
    RacerX -

    Without any more information than you've provided so far, I'll take a stab in the dark and suggest looking for a loose or missing ground wire. It may be that the ground is being picked up when the serial cable is available, and when it's not connected, the circuit is incomplete. Thus, you may be seeing the readings of a "floating" circuit.

    A sketch or schematic of how you have the pushbuttons and resistors set up would probably be quite helpful in troubleshooting this problem. Also, make sure the variable "result" is defined as a WORD, since its value can exceed 255, the maximum value for a BYTE variable.

    Regards,

    Bruce Bates

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-06-20 14:59
    How are you powering the BOE Rev. A?· I've heard of people experiencing leeching of power from the computer.· If that's happening you might not be getting enough when the Serial Cable is disconnected.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • RacerXRacerX Posts: 6
    edited 2006-06-20 20:09
    Currently I am powering the BOE with the 9v AC adapter.· Eventually, it'll be 6v from 4 AA batteries.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-06-21 18:44
    I'm going to assume that puts out a DC voltage, not AC...How much current though?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • RacerXRacerX Posts: 6
    edited 2006-06-24 18:33
    Its a 9vdc 1 amp power supply. I got it working like it should though. Bruce, who suggested a bad ground, nailed it. I redid a few things on it when I switched it to run off batteries. the BOE was drawing power from my board, now my board uses power from the boe. Musta been something iffy with my previous wiring. Thanks for the replies all!
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