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[wxsig] Fried CPU?

John Yost k3yjp at yahoo.com
Tue Jan 15 16:52:01 UTC 2008


Will,

No activity on the LCD during programing(or any other
time), just the backlite glow and the 1st and 3rd rows
show blocks.  If I turn the contrast up all four lines
display blocks.

Heartbeat led never flashes, has a steady 0.45 volts.
Same, fully populated or with every thing removed
including the button board

When the reset is pressed pins 1, 20 and 31 go to 0.07
volts, close enough to zero?

Looks like the cpu needs to "go to the shop" hi hi

Really appreciate your help with this.

john

--- William Beals <will at beals5.com> wrote:

> John:
> 
> When you try to do downloads, does the LCD panel
> show the text saying that
> it is waiting for the CPU?  If so, that is a good
> sign that the CPU may be
> OK.
> 
> Also, in my long batch of questions, I asked if the
> LED did any blinking at
> all when you tried powering up with as little
> plugged in as possible.
> 
> It is a very long shot, but in case you haven't
> tried it, also check to see
> that the CPU voltage (pins 1, 20,and 31) go down to
> zero volts when you push
> the reset button.
> 
> If the answers are Yes, nothing, and 0V, then I'd be
> willing to bet that the
> CPU is OK, but somehow the code got corrupted. 
> Believe it or not, that has
> been very rare.  I think it has happened twice to my
> knowledge--at least by
> folk communicating on this reflector.
> 
> Good point on needing the special crystal, I forgot
> about that!  Given that,
> your best bet may be to send me the CPU.  If it does
> turn out to be OK, I
> will just reprogram it and send it back.  If it is
> damaged somehow, I'll go
> digging for a spare around here and let you know
> what it cost me.
> 
> will
> 
> 
> 
> -----Original Message-----
> From: wxsig-bounces at lists.tapr.org
> [mailto:wxsig-bounces at lists.tapr.org] On
> Behalf Of John Yost
> Sent: Sunday, January 13, 2008 5:20 PM
> To: TAPR Weather Station SIG Mailing List
> Subject: [wxsig] Fried CPU?
> 
> 
> Will,
> 
> Thanks for guidance.
> 
> This was a working unit, almost a year, working
> perfectly.
> 
> Pins 1, 20 and 31  all 4.95v
> 
> P3 not installed and no solder bridges(I doubled
> checked).  After your email, I tried shorting 7 & 8
> to
> see if it might jump start it, nah.
> 
> U1, pins 2 & 6 are 9.7 and -9.5 respectively.
> 
> I have verified that the 32MHz osc is working by
> monitoring it on my IC7000.  Good strong sig from
> it.
> Also, reheated all the solder joints just to make
> sure
> I didn't have a bad one.
> 
> Tried, again, to load the firmware but it just sits
> there waiting for the cpu to respond.
> 
> What happened.  I was connecting the X1W-1 and X1W-2
> sensors and the AAG sensor to see if they all worked
> together before taking it outside.
> 
> I had connected the barometer several times due to
> my
> improper calibration.  This last time the jumper on
> P1
> was set to EXT and caused the T238's lcd to remain
> lite even when its power was disconnected.  It
> wasn't
> on long that way, but sometimes it doesn't take
> long.
> 
> I didn't think I could run the debugger tools with
> the
> 32MHz osc.
> 
> More thoughts?
> 
> Sure hate when I do oop's like this, fortunately not
> too often :)
> 
> john
> K3YJP
> 
> 
> 
> --- William Beals <will at beals5.com> wrote:
> 
> > John:
> > 
> > (putting this on wxsig as it may be helpful to
> > others)
> > 
> > Ouch!  I'm actually hopeful that your CPU isn't
> > fried though.  They are
> > amazingly tough buggers and in all my years of
> > playing with them, (and lots
> > of stupid moves to try and kill them), I have only
> > "succeeded" a few times.
> > 
> > Getting the LCD backlight is a good sign for power
> > being OK, but worth
> > checking some things a bit later, but first...
> > 
> > First best bet is to unplug everything from the
> > boards except power.  This
> > minimizes the possibility something external
> > (particularly the 1-wire stuff)
> > is causing the CPU to not power up correctly.  If,
> > with nothing else plugged
> > in, you still get no LED flashing or LCD activity,
> > then the problem is
> > definitely isolated to the board.  If things start
> > working, then you should
> > be able to quickly isolate what cable is causing
> the
> > problem.  If your
> > heartbeat LED is on the main board, having the LCD
> > and button board
> > unplugged gets you down to bare minimums.
> > 
> > 
> > Assuming things are still dead, check the voltage
> on
> > pins 1, 20, and 31 of
> > the CPU.  It should be very close to +5V.  If not,
> > then you may have enough
> > voltage for the backlight, but not enough for the
> > CPU to come up.  An oops
> > shorting VCC to GND on the CPU side can fry the
> > reset switch as I instigate
> > a reset by removing power.
> > 
> > Have you messed with P3 at all?  For normal use it
> > shouldn't be used.  If
> > you have any jumpers on it they can stop the CPU
> > from starting.  Shorting
> > pins 7 and 8 in particular have the CPU come up in
> > debug mode which looks
> > very dead unless you have a debugger hooked up.
> > 
> > Check pins 2 and 6 on the MAX232 chip (U1).  Are
> the
> > roughly +9V and -9V
> > respectively?  Being off won't necessarily kill
> the
> > CPU, but will give an
> > indication of the health of the power systems.
> > 
> > If none of those work, hopefully some of the data
> > gathered above will help
> > determine some future steps.  Also, if you have an
> > idea what got messed up,
> > that can give a hint as to what to try next.
> > 
> > If all these fail, the second-last resort is to
> try
> > and use the debugger
> > tools to reprogram the CPU in case somehow the
> flash
> > code got corrupted.
> > That's pretty involved, so will get to that later
> if
> > needed. If that doesn't
> > work then I think I can scrounge up a CPU.  I use
> > them for some other
> > projects as well, so buy a few extras.
> > 
> > will
> > 
> > -----Original Message-----
> > From: John Yost [mailto:k3yjp at yahoo.com] 
> > Sent: Saturday, January 12, 2008 9:26 AM
> > To: will at beals5.com
> > Subject: T238+ cpu
> > 
> > Will,
> > 
> > I believe I have cooked my cpu.  The T238 has been
> > working great for over a year now.  I was
> attempting
> > to add the x1w-1 and x1w-2 sensors to the system. 
> > Have problems getting the barometer to read
> properly
> 
=== message truncated ===



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