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PDB pulse generator question — Parallax Forums

PDB pulse generator question

paulc22paulc22 Posts: 7
edited 2007-08-20 17:52 in Learn with BlocklyProp
Hello.· I am trying to test my program which uses the COUNT instruction to count pulses on a pin.· I want to put some pulses on the pin, and I believe I could/should use the pulse generator on my professional development board.·
Trouble is, I don't know how to use the pulse generator.·

The PDB documentation for the pulse generator is very sketchy (well, actually it lacks a schematic), and it has only 3 short sentences on this feature.·

The PDB schematic doesn't help me much either.· I've read a lot of schematics before, but this one is confusing.· It has lots of pin connections at "GPIO" pins.· I guess GPIO means general purpose I/O, but I still don't know how to actually use it.·

All I want to know is how to use the pulse generator.· I assume it's already grounded on the board.· This seems like such a basic request.· Parallax obviously went through a bit of trouble putting the feature on the board.· Am I the only newbie who cannot figure this out?·

A simple paragraph indicating what we're basically doing, plus a good schematic, plus some sample code would be a GREAT benefit.

Please help.

Paul C
confused.gif·

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-19 16:53
    Paul,

    As this is a more advanced board there is less documentation/tutorials about it. The pulse generator is always sending out a pulse at the frequency listed below the LED lit up. By default at power up the pulse is 1 Hz (Square Wave). Each press of the button cycles through the frequencies (1 Hz, 10 Hz, 100 Hz, 1000 Hz/1 kHz). There really is nothing more to it. Those are the only frequencies you can get. Take care.

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    Chris Savage
    Parallax Tech Support
  • paulc22paulc22 Posts: 7
    edited 2007-08-19 22:47
    Hi Chris.· I have another problem as well.· Each time I press the push button for the pulse generator, it doesn't change from the highest frequency.· I don't have the board in front of me, but it's the one on the far right.· When I first got the board, it would cycle w/each press, but not any more.· Is something fried?· I didn't hook anything to it when it stopped cycling w/each pushbutton click.

    paul
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-20 15:29
    Paul,

    It seems like this is something that recently stopped working? It is hard to say what might be happening. To date I haven’t seen the pulse generator fail on any of these boards.

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    Chris Savage
    Parallax Tech Support
  • paulc22paulc22 Posts: 7
    edited 2007-08-20 17:18
    Yeah, this just happened about a week ago.· Do you have any diagnostics programs or methods I could use to troubleshoot this?

    The PDB documentation in the pulse generator area is very sketchy.· Do you have any more info.· It appears to use a processor IC to do it, and I was surprised it didn't just use a timer or similar (LM555).

    Thanks.

    Paul
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-20 17:52
    Paul,

    There is no troubleshooting you can do, save testing the output frequency at each value. The reason for using the PIC instead of a 555 is that the PIC can handle changing the output by using a button press. This would be significantly more difficult to do with a 555 Timer. You can run a wire from the signal generator output into the audio amplifier input. When the pulse is on 1 you should hear a kind of tick from the speaker. When the setting is on 10 you should hear a rapid clicking. When it is on 100 you should hear a low tone and on 1000/1K you should hear a higher pitch tone. Take care.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
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