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O'Scope Question — Parallax Forums

O'Scope Question

Fast MiconFast Micon Posts: 16
edited 2005-04-09 02:57 in BASIC Stamp
This is the Optascope plot of a led connected to a Stamp 1 pin.· The code that generates this is something like this:

LOW 7
do something
TOGGLE 7
do something
TOGGLE 7
return to main program

Why the voltage goes from 0V to 1V, then goes to 5V, then goes back to 1V before dropping to 0V again?
bmp
bmp
Strange Behavior.bmp
1M

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-03-21 00:43
    It would be helpful to see the whole program and know what is connected to the pin.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • Fast MiconFast Micon Posts: 16
    edited 2005-03-21 00:47
    Here it goes:

    Main:
    · LOW pREDE···· ······················'Enables LTC1487 receiver
    · SERIN pRODI, cBaud, ($AA), vAddress, vCommand, vCounter···'Waits for sync byte, match ID and then reads command
    · IF vAddress <> cMyID THEN Main···············'Ignores message if not for the node
    · vCounter = vAddress + vCommand - vCounter
    · IF vCounter <> 0 THEN Main·················'Loops if checksum is not correct
    · IF vCommand = $00 THEN CircuitOff··············'Changes the behaviour of pActivity to signal that circuit is off
    · IF vCommand = $01 THEN CircuitOn··············'Changes the behaviour of pActivity to signal thet circuit is on
    CircuitOff:
    · LOW pActivity
    · GOTO StartRead
    CircuitOn:
    · HIGH pActivity
    StartRead:
    · GOSUB ReadTemp·······················'Reads the raw temperature parameters
    · TOGGLE pActivity
    · GOSUB XmitTemp
    · PAUSE 40
    · TOGGLE pActivity
    · GOTO Main
    · END

    I have a led attached to pActivity (which is I/O 7) with a 470ohm resistor.· The pin is sourcing.


    ·
  • BeanBean Posts: 8,129
    edited 2005-03-21 01:05
    The COMPLETE program would help more.
    Most likely you are setting the pin to an input somewhere, but without the complete program that's just a guess.
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out· the "SX-Video Display Module"

    www.sxvm.com

    "A problem well defined, is a problem·half solved."
    ·
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-03-21 01:11
    The issue could be the use of TOGGLE -- it reads the state of the output port and then swaps it.· I suggest that you initialize the LED output to a known state before TOGGLE ever has a chance to run.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • Fast MiconFast Micon Posts: 16
    edited 2005-03-21 01:51
    Here goes the complete program:



    The schematic goes here:



    The other problem I have is very strange too.· When vCommand is $00 the progam works, with the strange behavior explained before.· When ·vCommand is $01 the Stamp resets.

    I really don't understand....
    bas
    bas
    Sensor Temperatura Remoto.bas
    7K
    Sensor.jpg
    909 x 765 - 96K
  • BeanBean Posts: 8,129
    edited 2005-03-21 02:26
    Sounds like you are drawing too much current at some point. This would explain the resetting and the odd voltage level.
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Check out· the "SX-Video Display Module"

    www.sxvm.com

    "A problem well defined, is a problem·half solved."
    ·
  • Fast MiconFast Micon Posts: 16
    edited 2005-04-09 02:57
    I have checked everything and calculated currents again. No excesses whatsoever.

    I finally replaced the BS1 with a new one............and all works perfectly well again. I guess I have an ESD damaged BS1....

    Regards,

    Fernando
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