AVR-Chat

1. For some reason, at power-up (4.5V from linear on-board regulator from PC 5V PSU) the microcontroller starts up temporarily but then stops (or goes to microcontroller heaven). 

I assume you have 5 volt device (Micro)- but stated 4.5 v supplied to it.... This seems to low for anything to be dependable..for a 5 volt device. Remember you stated it worked fine without the linear regulator, that may be do to the fact that the micro was getting the full 5 volts and was happy.

I do think you're right Mike, as it started after I put the linear regulator in, just to protect the microcontroller from the big bad PC PSU, but I want to know WHAT IS IT!

I was wondering what inspired you to protect the microcontroller from the big bad supply PC PSU with the linear regulator in the first place, I would assume the PSU is already regulated. If dirty supply you could add filter. If worried about over voltage,a zener perhaps. It just appears from what you wrote that the problem did not exist until you added the Linear Regulator...Then the problem appeared...This at least can be reversed back to original (without the Linear Regulator) to see if the problem disappears. That would just tell you that a different approach may be necessary.

Also, looking at the reset line with your scope at power up may reveal something. Just a thought. Such as soft on the pull-up (ie. RESET GLITCH) should be nice and clean. but my gut tells me "Power"

Hoping your making progress.
Regards, Mike


  ----- Original Message ----- 
  From: Cat C 
  To: avr-chat@yahoogroups.com 
  Sent: Thursday, March 11, 2010 1:13 PM
  Subject: RE: [AVR-Chat] Code stuck waiting for SPI transmission but only after power-up. (ATMega644P)


    

  I do think you're right Mike, as it started after I put the linear regulator in, just to protect the microcontroller from the big bad PC PSU, but I want to know WHAT IS IT!

  I'm now wondering: Is it possible that the Big Bad PC PSU broke my microcontroller in such a way that it generally works, but something... doesn't?

  Thanks,

  Cat

  > To: AVR-Chat@yahoogroups.com
  > From: benoitmc2@msn.com
  > Date: Thu, 11 Mar 2010 11:54:22 -0800
  > Subject: Re: [AVR-Chat] Code stuck waiting for SPI transmission but only after power-up. (ATMega644P)
  > 
  > Cat,
  > 
  > All you emails seems to me to somehow keep pointing to Power Supply.
  > BrownOut condition during start-up?
  > 
  > If I press the reset button all is fine, so maybe strange things happen because power might go up too slow.
  > 
  > Can you verify this, purhaps a different supply? Hopefully.
  > 
  > Wish I could be of more help.
  > 
  > Mike
  > 



  [Non-text portions of this message have been removed]



  

[Non-text portions of this message have been removed]