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[wxsig] RE: T238+ cpu fried?

John Yost k3yjp at yahoo.com
Sun Jan 13 20:54:00 UTC 2008


Thanks for guidance.

This was a working unit, almost a year, working

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 :)


--- 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
> so have had in on and off many times recalibrating
> it,
> still reads about 20mb high.  
> The problem is that on one of the hookup attempts
> the
> jumpers were not set properly and I believe feed
> some
> power back to the t238, cuz the lcd went blank -
> backlite with squares instead of text.
> I've checked the components and all seem ok.  Just
> attempted to reflash the cpu but it is just sitting
> there, so no hope there.
> So the question is, how much would a programmed cpu
> cost, assuming they are still available, and are you
> the right person to contact for one?
> thanks for the project, wx has never been so much
> fun
> or interesting...and I always liked messing with wx
> stuff.
> john K3YJP
> ________
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