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BS2 I/O pin voltage dip — Parallax Forums

BS2 I/O pin voltage dip

ayoungayoung Posts: 2
edited 2007-09-16 04:21 in BASIC Stamp
Hello,

I have discovered an issue with the BS2 that I cannot figure out. I am not sure if it is a faulty BS2, or if something else could be causing the issue.

I have 4 LEDs (LED with built in resistor) connected to 4 output pins on the BS2. I can manipulate all the LEDs with no problem: flash, on/off, etc. However, when I turn any one of the pins HIGH, the LED lights fine but has a noticeble flicker every 3 to 4 seconds. It does not matter if one LED is lit or all 4 are powered, they will all "flicker" at the same time. There is nothing in the program that would cause this, the only commands are the "HIGH" statement.

It is not a faulty LED, power supply, or voltage regulator·because I can wire the LED directly to the output of the·regulator and the LED does not flicker. I have a digital multi-meter, and although not very responsive, it will show a dip in voltage on the output pin corresponding to the LED flicker. I measure the power supply outlet and regulator outlet·voltage with the DMM and it is rock solid.

The BS2 works fine on inputs, serial communication, etc. The outputs work fine except for the uncommanded flicker.

Has anyone seen this before? Is this possible a BS2 that is going out? It has been used for several years but I have never used it in an application where I had to have a steady output. So, I am not sure if this is a new problem or if it has been there all along.

Thank you in advance for your help and any suggestions! I appreciate all the input on this forum. It is a valuable resource.

Thanks,

AY

Comments

  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-09-16 01:55
    My guess is that the program has ENDed, or is going into a cycle of SLEEP. When the Stamp wakes up every couple of seconds, the pins briefly (~15 mS) become inputs, and the LEDs would flash off. To avoid that, end the program with a STOP command (which keeps the Stamp from going to sleep), or keep it running in a loop.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • allanlane5allanlane5 Posts: 3,815
    edited 2007-09-16 01:58
    Yup, seen this before. This happens when you "END" the program, or do a long "Sleep" -- every 2.5 seconds or so (I forget the exact number) the BS2 'wakes up', sets all pins briefly as inputs (which would turn off an output) then restores the pin states to that commanded by your program.

    The solution to this is to use "Stop", or to put the BS2 into a tight loop like:

    Delay:
    GOTO Delay
  • ayoungayoung Posts: 2
    edited 2007-09-16 02:01
    Wow!

    Thank you Tracy and Allenlane5! That is it. Works perfectly!

    Thanks again to all who contribute to the forum. Have a great evening.

    AY
  • allanlane5allanlane5 Posts: 3,815
    edited 2007-09-16 02:03
    Ah! Great minds think alike.
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-09-16 04:21
    And within 15 minutes too!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
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