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  1. #21
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    Okay, so I reiterate what was said before.
    Increase the RC time constant of the reset so that nRST goes up just after Vcc got steady.
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    •   Alt16th February 2018, 17:07

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  2. #22
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    Hi,

    Here are the transient responses where yellow is the input voltage and blue is the reset voltage
    This makes no sense to me.
    Usually the RESET circuit is supplied by the same supply voltage than the microcontroller.
    But in your case the RESET output voltage is higher than the supply voltage.

    Are you sure you didnīt mix the colors? --> blue= supply, yellow = RESET

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. Thank you.



  3. #23
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    Quote Originally Posted by KlausST View Post
    Hi,


    This makes no sense to me.
    Usually the RESET circuit is supplied by the same supply voltage than the microcontroller.
    But in your case the RESET output voltage is higher than the supply voltage.

    Are you sure you didnīt mix the colors? --> blue= supply, yellow = RESET

    Klaus
    Yes, that's right, it is vice versa. I wrote it wrong.
    Cheers,
    Ogulcan



    •   AltToday, 07:41

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  4. #24
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    In a forum post, I read that noise in oscillator may cause the oscillator to lock and prevent the MCU booting unless reset is applied.

    I checked my oscillator behavior and sow that I have a noisy oscillator compared to my previous design. So, do you have any suggestions based on this?

    Thanks,
    Ogulcan
    Cheers,
    Ogulcan



  5. #25
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    Hi,

    How did you measure the "noisy" oscillator? Show the measurement results.

    Best is to keep on the datasheet recommendations.
    * Read the microcontroller datssheet oscillator section
    * read the XTAL datasheet

    Additionally you need to use a good PCB layout with solid GND plane, power supply capacitors next to each power supply pin, short wiring to the XTAL, low impedance connection of XTAL_capacitors to GND.
    This safes from noisy / unreliable oscillator clock.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. Thank you.



    •   AltToday, 10:58

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  6. #26
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    Quote Originally Posted by KlausST View Post
    Hi,

    How did you measure the "noisy" oscillator? Show the measurement results.

    Best is to keep on the datasheet recommendations.
    * Read the microcontroller datssheet oscillator section
    * read the XTAL datasheet

    Additionally you need to use a good PCB layout with solid GND plane, power supply capacitors next to each power supply pin, short wiring to the XTAL, low impedance connection of XTAL_capacitors to GND.
    This safes from noisy / unreliable oscillator clock.

    Klaus
    You can see it by oscilloscope, but when you take the screenshot, there is not much difference, but there is a significant difference when you see it in real. I need to take a video I guess.

    I tried to do my best for the oscillator in general. But there are too much signal lines around. I put as much via around oscillator as possible but I guess it did not help.
    Cheers,
    Ogulcan



  7. #27
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    Re: MCU does not boot on power up, only starts when reset button is pressed

    Hi,
    You can see it by oscilloscope, but when you take the screenshot, there is not much difference, but there is a significant difference when you see it in real. I need to take a video I guess.
    you have a ROHDE & SCHWARZ scope...it should be no problem to show us what you mean.

    I tried to do my best for the oscillator in general. But there are too much signal lines around. I put as much via around oscillator as possible but I guess it did not help.
    This is no useful information. Neither for us nor does it help you with your problem.
    Why donīt you show us your PCB layout? Too secret?

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. Thank you.



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