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Re: [ORE_bits] Re: MegaOre

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  • Aaron Ramsey
    ... Well, almost one year to the day since I played with this board. Its been in the back of my head bugging me. Fired it up today and verified that the 3.3V
    Message 1 of 38 , Nov 1, 2009
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      Aaron Ramsey wrote:
      > DOH! Fire it up last night, everything was looking good with 3.3V and 5V
      > within 0.001V according to my fluke. When to port over some code from my
      > micro-ore and discovered that pretty much every register was named
      > something different. Spent last night tweaking the code and finally had
      > a chance to run it this afternoon.
      >
      > When I powered up the board the speaker was making wacky noises and I
      > could smell something a little funny.... poke around and my processor is
      > smoking hot. I had just changed the crystal from 15M to 10M but didn't
      > think that should cause a problem. Measured the logic voltage and its at
      > 6V! Holy smokes! Pull off the regulator and put on a new one and back to
      > 3.3V.
      >
      > I'm thinking that this regulator must be sensitive to static
      > electricity. I had it on my bed last night when I was playing with the
      > code. :-/
      >
      > The processor seems to still be ok.... only time will tell if I blew
      > anything else on the board. ARG!
      Well, almost one year to the day since I played with this board. Its
      been in the back of my head bugging me.

      Fired it up today and verified that the 3.3V regulator was outputting
      almost 6V. Debated about replacing the regulator and various components
      yet again, then decided that I'd rather be using the board instead of
      debugging the regulator, so I found a linear 3.3V regulator in my junk
      pile and figured out a way to remove the switching regulator and put the
      linear reg in its place with minimal cuts and straps.

      Pulled the massive inductor off and then flipped the board over to
      remove the switching IC..... hold on... what the heck.... I notice a
      resistor which only has solder on one side of it..... DOH! The switcher
      was a resistor divider which sets the output voltage through a feedback
      loop.... one of those resistors was only contacting the PCB when the
      moon was aligned with the stars. Man... I feel like an idiot for missing
      that way back when.

      Still not sure what is smoked on the board but at least I've got a
      fighting chance now. The LCD looks to still be good.

      http://aaronramsey.com/public/megaore-schematic.pdf

      Aaron
    • Aaron Ramsey
      And the carnage continues! ADXL330 was destroyed so now I ve got a shiny new 335 sitting on there. The LCD screen turned out to be smoked.... the backlight was
      Message 38 of 38 , Nov 10, 2009
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        And the carnage continues! ADXL330 was destroyed so now I've got a shiny new 335 sitting on there. The LCD screen turned out to be smoked.... the backlight was still working but wouldn't talk to me over SPI. Plopped a new on in there (alway buy 2!!) and I've got pretty little graphics now.

        Next step is to talk to the RF and see if it made it or not. I'm going to end up having replaced most of the ICs on the board by the time I'm done. ;-) All because I missed one little solder joint. Well, that's a good way to learn not to skip the visual inspection step after assembling. <grin>

        Aaron


        Aaron Ramsey wrote:

        Aaron Ramsey wrote:
        Aaron Ramsey wrote:
        The processor seems to still be ok.... only time will tell if I blew 
        anything else on the board. ARG!
            
        Still not sure what is smoked on the board but at least I've got a 
        fighting chance now. The LCD looks to still be good.
          
        Processor was smoked. ;-) Now that its been replaced and I've got LEDs up and blinky, I need to start writing code to test out all the other stuff that I might have smoked. ADXL330 accelerometer claims it can handle 7V so it might have made it. The MRF24J40MA RF module probably didn't survive given that the other PIC blew up, but you never know. Most of the stuff is easy to replace, aside form the ADXL330 so I should be rolling along pretty soon.

        Aaron

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