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io pin voltages high in "low" state — Parallax Forums

io pin voltages high in "low" state

SybilSybil Posts: 12
edited 2005-10-27 15:47 in BASIC Stamp
shakehead.gif please help my io pins are showing ~2 volts in a low condition. any body have any suggestions as to the problem/solution?
thanx

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-27 02:00
    Could you provide more information please?· How did you determine this?· What is your power supply and what code are you running?· And, more importantly, what's connected to the I/O lines?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • SybilSybil Posts: 12
    edited 2005-10-27 03:17
    discovered the problem when doing Chapter 3 ReadPushButtonState.BS2 on page 77 of What is a Microcontroller Student Guide:

    DO
    DEBUG ? IN3
    PAUSE 250
    LOOP

    Have used both 18v power supply and 9v battery.

    Ran the program with nothing attached to the I/O pins and debug terminal displayed 1's instead of the expected 0's. Checked the I/O pins with a multimeter and they showed approx 2 - 3 volts. Also, Vdd only reads 3.8v

    This is a OEM BS2 that I hooked to a breadboard.

    Post Edited (Sybil) : 10/27/2005 3:28:58 AM GMT
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-10-27 03:40
    If you were expecting 0's with nothing attached did you have a pull-down? You must not let an input pin float.

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    Jon Williams
    Applications Engineer, Parallax

    Post Edited (Jon Williams (Parallax)) : 10/27/2005 3:43:44 AM GMT
  • SybilSybil Posts: 12
    edited 2005-10-27 04:13
    thank you, that explains the voltageson the io pins , but i have another problem with vdd. its putting out only 3.7 v and any excercise from the guide that i do involving vdd fails........led's dont light, the pushbutton excercise doesnt respond to the push button
    thanx again
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-10-27 04:20
    You either have a power supply problem, or something on an output that is swamping your Vdd.

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    Jon Williams
    Applications Engineer, Parallax
  • Bruce BatesBruce Bates Posts: 3,045
    edited 2005-10-27 04:27
    Sybil -

    What are you using for a power supply, and how is it connected to the Stamp carrier board?

    Regards,

    Bruce Bates
  • SybilSybil Posts: 12
    edited 2005-10-27 05:11
    am set up to use either a 18v wall adapter or 9v battery to the vin and vss.... same problem with either one

    i get the 3.7 v on the vdd with nothing attached to the output pins

    Post Edited (Sybil) : 10/27/2005 5:14:48 AM GMT
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-10-27 05:29
    Disconnect EVERYTHING except the power supply and try again. Use the 9v supply; we don't recommend anything over 12v on Vin.

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    Jon Williams
    Applications Engineer, Parallax
  • SybilSybil Posts: 12
    edited 2005-10-27 05:53
    the sheet that came with the oem bs2 said 6-24 volts on the vin but regardless i disconnected everything and got 4.9 volts (with 9v battery)at the vdd pin on the board, i guess there is an issue with the ribbon cable i used to connect it to the breadboard. btw a 40 pin ribbon cable from a computer mates nicely to the oem bs2's 20 pin connector, i just cut off one connector and soldered it to the bread board
    do you think the small diameter of the wires could be causing my problem?


    thanx jon

    Post Edited (Sybil) : 10/27/2005 6:00:05 AM GMT
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-10-27 06:03
    It could be, or you could have bad connections. I never use that stuff -- big pain in the patootie [noparse][[/noparse]sp?]. Better to stick with 22/24 gauge wire and use female crimp sockets.

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    Jon Williams
    Applications Engineer, Parallax
  • SybilSybil Posts: 12
    edited 2005-10-27 06:11
    lol
    I am hitting the sack so i wont be a pain in your patootie anymore tonight
    thanx again,
    sybil
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-27 14:30
    Sybil said...
    the sheet that came with the oem bs2 said 6-24 volts on the vin but regardless i disconnected everything and got 4.9 volts (with 9v battery)at the vdd pin on the board, i guess there is an issue with the ribbon cable i used to connect it to the breadboard. btw a 40 pin ribbon cable from a computer mates nicely to the oem bs2's 20 pin connector, i just cut off one connector and soldered it to the bread board
    do you think the small diameter of the wires could be causing my problem?
    thanx jon
    Sybil,

    ·· The BS2-OEM can run up to 24VDC on the Vin pin only.· This is okay on the OEM models of BASIC Stamp since they use the same regulator as most of our Development Boards.· My question is, is this a kit you built?· If so, perhaps there is another problem on the board.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-10-27 15:43
    Thanks, Chris, I missed the OEM part -- was a late night last night....

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    Jon Williams
    Applications Engineer, Parallax
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-27 15:46
    Understood, but regardless of his power input...Either something's wrong with the supply or something's wrong with the board.· That or you are reading the voltages incorrectly (Or bad meter) but your readings are not only incorrect, but the interpreter shouldn't be running at those voltages.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-10-27 15:47
    She discovered the problem was with her wiring loom -- using ribbon cable (the horror!) and probably has a duff connection.

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    Jon Williams
    Applications Engineer, Parallax
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