Thanks everyone for the advice, both on and off list.
I do see voltage transitions on P0.5 of the C8051F330D, which is pin 19
on the DIP version of the microprocessor. So it appears that the serial
data pulses are making it from the Thunderbird to the input to the
microprocessor.
However, voltage as measured from the microprocessor VDD to GND (pins 6
to 5) is 4.94VDC. The C8051F330D manufacturer's spec for VDD is 4.2VDC
"Absolute Maximum Rating." Didier's speculation seems on point . . .
overvoltage on the microprocessor has likely damaged it.
There is a caveat: The way the iCruze is constructed has the C8051F330D
sandwiched between two PCB's and not readily visible. So I am assuming
that the microprocessor is a C8051F330D, but that is not verified (at
least not by me). Getting at the microprocessor requires desoldering the
16-pin header which connects its PCB to the display PCB.
Not sure where to go from here . . . trash can?
Steve
On 6/5/2011 4:25 PM, shali...@gmail.com wrote:
Check that the serial data is going to the processor. The schematic is on my
web site www.ko4bb.com look for GPS Monitor
You should see the inverted serial data on the processor pin that is driven by
the NPN transistor used as an inverter and level converter. I forgot the pin
number and I am not in range of a computer.
While you are at it, check that the processor is powered from 3V. Some units
sold by fluke.l applied 5V to the processor. If you see 5V, the processor is
probably toast.
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: Steve<stev...@suddenlink.net>
Sender: time-nuts-boun...@febo.com
Date: Sun, 05 Jun 2011 15:23:55
To: Discussion of precise time and frequency measurement<time-nuts@febo.com>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] fluke.l monitor for Thunderbolt
David,
Thanks for the suggestions. There is continuity to the PCB in the iCruze.
Not sure what to make of the voltage levels on pin 2 of the DB9. Using
just a scope connected to the Thunderbolt, the voltage switches from -10
to +10. With the laptop connected, it switches from -9 to +9. With the
iCruze connected, it switches from -6 to +6.
I don't know if the -6 to +6 is normal, but it seems low to me for RS-232.
Taking the troubleshooting to the next level on the iCruze involves
desoldering a 16-pin header. I dunno . . . .
Steve
On 6/5/2011 4:56 AM, David Bobbett wrote:
Steve,
The two lines of text are what the iCruze will display when it thinks
it doesn't have any data. The RS232 input on my system can be
unplugged and that is exactly what is shown on the display in those
circumstances.
Personally, I would start with the simple stuff, just continuity check
the '232 lines from the iCruze plug all the way back to the PCB.
If that doesn't work, there's a circuit diagram of the device on
Didier's web site.
73 de David, G4IRQ
On 04/06/2011 22:17, Steve wrote:
About a year ago I installed one of the iCruze monitors from fluke.l
on a Thunderbolt GPS receiver. I paralleled the iCruze with the
serial port on my laptop PC. Sometimes the PC was connected,
sometimes not. The iCruze worked OK either way.
Last week I noticed the iCruze was no longer functioning as before.
It now alternates between two lines of text: "Trimble LED Monitor"
and "Waiting for GPS". Whether the laptop is connected or not does
not make a difference. The laptop running tboltmon works ok with or
without the iCruze paralleled across the serial data line.
I substituted another Thunderbolt and saw the same results.
The iCruze has about 10VDC on its power input.
I not particularly competent at serial communications or
oscilloscopes, but on the DB9 feeding the iCruze I can see the
transition of voltage from about -6VDC to about +6VDC. I didn't look
at those voltage levels when I installed the iCruze last year so I
don't know if that's what it has always been or not.
I have rebooted the iCruze several times as well as the Thunderbolt
and laptop, no change in iCruze behavior.
Any advice as to where to go from here?
Thanks.
Steve
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