12F683, 12LF1840 - Port ON/OFF speeds are different!


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  1. #1
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    Default Re: 12F683, 12LF1840 - Port ON/OFF speeds are different!

    Well, I asked that before...

    I use 2 channels as you can see from scope, and I need to have adjustable dead time between outputs, to avoid short circuit. Is it possible to synchronise 2 PWM generators in that way?

  2. #2
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    Default Re: 12F683, 12LF1840 - Port ON/OFF speeds are different!

    I think that you will not be able to do phase shift (delay) between 2 PWM outputs in same PIC. With 2 PIC's this might bee possible.

    If your system is so time critical that GOTO-command will generate problems then how you will monitor and adjust outputs?
    Therefore I don't see any other options than using HW modules (PWM) and PIC code just monitor and control HW module(s).

  3. #3
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    Default Re: 12F683, 12LF1840 - Port ON/OFF speeds are different!

    With another pic, it can be done easy.

    PIC18F14K22 have everything what you need:
    Enhanced Capture/Compare/PWM (ECCP)
    module:
    - One, two or four PWM outputs
    - Selectable polarity
    - Programmable dead time
    - Auto-shutdown and Auto-restart
    - PWM output steering control
    And all that controlled from comparators outputs.
    If comparator output is low or high(selectable) pwm outpu can go to some state, high or low.
    You can turn on/off hysteresis on comparators, etc...
    Just read this 404 pages and you will know everything you need

  4. #4
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    Default Re: 12F683, 12LF1840 - Port ON/OFF speeds are different!

    Another guess is that PIC18F14K22 won't be available in SOIC-8....

  5. #5
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    Default Re: 12F683, 12LF1840 - Port ON/OFF speeds are different!

    Take a look at the 12F1501, it might do what you want and comes in 8pin package.

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