Discussion:
Samsung GPSDO : Chinese surplus
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gandalfg8--- via time-nuts
2018-09-20 13:55:10 UTC
Permalink
These are Samsung's version of the "UCCM" series of GPSDOs. Lady Heather now works with them. I had to tweak the code to handle their funky/erratic end-of-line sequences... various versions of CR/LF, LF, LF/CR. Their STATUS screen and some message responses are also a bit different. They do tell you the antenna current.......


-----------------------------


I'm not sure, but to borrow from Orwell, I do suspect that some Samsung UCCM modules may be more equal than others, so here's a warning to the curious, sorry, M R James that time:-)........


Anyways, after Greg posted information about these earlier this month I bought one of the STP2945LF versions from Ebay auction 332792680396 and the one that arrived a couple of days ago is the actual item currently pictured in that auction, condition is very good and a flatstrip interface connector was an unexpected bonus so certainly no problem there.


Whether or not I've just missed something and ended up reinventing the wheel I don't know, but after first believing wrongly that this unit must be faulty here is what I've found so far......



The supply voltage seems to be quite critical, inasmuch as the alarm light is on if the supply is below approx 5.5 volts, it certainly doesn't like 5 volts, and it comes on again if the supply is increased to just over 6 volts. At the upper limit there's no immediate obvious other effect but at the bottom limit the unit seems to drop immediately into holdover, this from observing plots on a Pendulum counter.
Even when the supply is ok the alarm light is amber rather than green but not sure what that's trying to tell me. Trying different antennas and even a resistive load at the antenna socket makes no difference.



At the moment Lady Heather doesn't seem to be hapy with this one, despite forcing baud rate and receiver type she just didn't want to know at first and insisted there was no data to be seen from the COM port, and initially the unit itself didn't seem to be doing anything very useful either



However, running it into Hyperterminal did show it booting up at 57600, 8-N-1 as expected, and eventually I discovered that this unit has two options for Reference type, GPS or EXT, EXT presumably "external" and I assumed referring to what was supposed to be feeding whatever this was used in, and it defaults to EXT whenever the unit is started or after a hard or soft reset. Fortunately it's possible to run a "Ref : Type GPS" command and the activity LED quickly confirmed that it's now behaving as expected.

If I run a diagnostic:loop command though it's so far always returned a figure of +1.062E-7 for the OCXO but also states that EXT is "unavailable" which might even suggest that the EXT input is an expected input to the GPSDO itself.

Purely speculation of course, and the 1PPS is definitely an output at the moment...



Next oddment, trying yet again to let Lady H see it I left the GPSDO running and terminated the connection in hyperterminal and started Lady H again with the receiver preset as UCCM, still nothing until I brought up the command line help screen and then Lady H started taking data in behind it only to stop again when I closed the help screen.

This was very erratic though, sometimes she'd stay after the help screen was closed but sometimes lock and sometimes randomly updating, either way she certainly wasn't having a good day:-)


What Lady H did manage to do was to switch the output to the continuous data stream mode and the only way I've found so far of stopping this is a hardware or software reset, either of which then sets the Reference typ to EXT again:-(


So that's it for now, still playing but I did think it was worth alerting other potential buyers as to what they might expect.



Not all doom and gloom though, and believe it or not I'm even inclined to recommend it, Lady H has shown over a dozen sats with good signal levels at times, that's pretty remarkable for here, and it does lock quickly and conditioning looks good. It would be interesting to see if holdover improves though, and if it could be persuaded to default to GPS at start up that might perhaps be a bit more useful:-)


Nigel, GM8PZR




















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Mark Sims
2018-09-20 18:26:42 UTC
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I had to make several changes to Lady Heather to work with these... you may have an earlier version.

How are you connecting the serial port? In the photo, I did not see the row of four holes that is on the Trimble / Symmetricom versions.
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gandalfg8--- via time-nuts
2018-09-20 20:55:09 UTC
Permalink
I had to make several changes to Lady Heather to work with these... you may have an earlier version.


How are you connecting the serial port? In the photo, I did not see the row of four holes that is on the Trimble / Symmetricom versions.



---------------
Hi Mark



The serial port connections are on the 50 pin flatstrip header, as per diagram here......


http://tipok.org.ua/node/53



That's based on the Trible/Symmetricom versions and is shown with the connector removed but so far what I've checked matches up.
Fortunately my unit was supplied with a breakout board to convert the flatstrip to a double row of 0.1" spaced holes, and a couple of rows of header strip plus an old flat SCSI cable fitted a treat:-)



I realised there must be variations with this one over and above what you'd sorted earlier but thought it worth a mention in case it gave you any pointers, the real issue though is still that as it stands it can never boot into GPS mode without outside intervention anyway.
I did wonder if it could have received the appropriate configuration commands for whatever unit it was sat in but that should have been obvious to anyone who powered one up, which it might have been of course:-)


For now I've switched to the view that this one may have either a hardware or software fault that's preventing it booting up properly and am currently awaiting further response from the seller.


As it stands it's certainly not a very practical option if it needs a permanently attached PC to manage the boot up, although once booted it is looking quite good, as is the little Ublox LEA-6T.


I'm still intrigued though by the very existence of that EXT/GPS software switch as a configuration option for the GPSDO itself, and wondering just what EXT might actually imply in this instance.



Nigel GM8PZR








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Mark Sims
2018-09-20 22:58:49 UTC
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All the UCCM receivers have a EXT option... but most refer to it as LINK. Heather sets it to GPS on startup. I believe LINK/EXT selects an external PPS/PP2S provided by the base station. I think they normally operate it in GPS mode and switch to EXT if the GPS goes down.

------------------
Post by gandalfg8--- via time-nuts
I'm still intrigued though by the very existence of that EXT/GPS software switch as a configuration option for the GPSDO itself, and wondering just what EXT might actually imply in this instance.
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mimitech mimitech
2018-09-21 12:25:11 UTC
Permalink
Hi, Nigel
To select GPS as the default input port, it was required to tie PIN 39 (of
50-pin FPC connector) to GND.
Subject: [time-nuts] Samsung GPSDO : Chinese surplus
These are Samsung's version of the "UCCM" series of GPSDOs. Lady
Heather now works with them. I had to tweak the code to handle their
funky/erratic end-of-line sequences... various versions of CR/LF, LF,
LF/CR. Their STATUS screen and some message responses are also a bit
different. They do tell you the antenna current.......
-----------------------------
I'm not sure, but to borrow from Orwell, I do suspect that some Samsung
UCCM modules may be more equal than others, so here's a warning to the
curious, sorry, M R James that time:-)........
Anyways, after Greg posted information about these earlier this month I
bought one of the STP2945LF versions from Ebay auction 332792680396 and the
one that arrived a couple of days ago is the actual item currently pictured
in that auction, condition is very good and a flatstrip interface connector
was an unexpected bonus so certainly no problem there.
Whether or not I've just missed something and ended up reinventing the
wheel I don't know, but after first believing wrongly that this unit must
be faulty here is what I've found so far......
The supply voltage seems to be quite critical, inasmuch as the alarm
light is on if the supply is below approx 5.5 volts, it certainly doesn't
like 5 volts, and it comes on again if the supply is increased to just over
6 volts. At the upper limit there's no immediate obvious other effect but
at the bottom limit the unit seems to drop immediately into holdover, this
from observing plots on a Pendulum counter.
Even when the supply is ok the alarm light is amber rather than green but
not sure what that's trying to tell me. Trying different antennas and even
a resistive load at the antenna socket makes no difference.
At the moment Lady Heather doesn't seem to be hapy with this one, despite
forcing baud rate and receiver type she just didn't want to know at first
and insisted there was no data to be seen from the COM port, and initially
the unit itself didn't seem to be doing anything very useful either
However, running it into Hyperterminal did show it booting up at 57600,
8-N-1 as expected, and eventually I discovered that this unit has two
options for Reference type, GPS or EXT, EXT presumably "external" and I
assumed referring to what was supposed to be feeding whatever this was used
in, and it defaults to EXT whenever the unit is started or after a hard or
soft reset. Fortunately it's possible to run a "Ref : Type GPS" command and
the activity LED quickly confirmed that it's now behaving as expected.
If I run a diagnostic:loop command though it's so far always returned a
figure of +1.062E-7 for the OCXO but also states that EXT is "unavailable"
which might even suggest that the EXT input is an expected input to the
GPSDO itself.
Purely speculation of course, and the 1PPS is definitely an output at the
moment...
Next oddment, trying yet again to let Lady H see it I left the GPSDO
running and terminated the connection in hyperterminal and started Lady H
again with the receiver preset as UCCM, still nothing until I brought up
the command line help screen and then Lady H started taking data in behind
it only to stop again when I closed the help screen.
This was very erratic though, sometimes she'd stay after the help screen
was closed but sometimes lock and sometimes randomly updating, either way
she certainly wasn't having a good day:-)
What Lady H did manage to do was to switch the output to the continuous
data stream mode and the only way I've found so far of stopping this is a
hardware or software reset, either of which then sets the Reference typ to
EXT again:-(
So that's it for now, still playing but I did think it was worth alerting
other potential buyers as to what they might expect.
Not all doom and gloom though, and believe it or not I'm even inclined to
recommend it, Lady H has shown over a dozen sats with good signal levels at
times, that's pretty remarkable for here, and it does lock quickly and
conditioning looks good. It would be interesting to see if holdover
improves though, and if it could be persuaded to default to GPS at start up
that might perhaps be a bit more useful:-)
Nigel, GM8PZR
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gandalfg8--- via time-nuts
2018-09-21 16:56:12 UTC
Permalink
Hi, Nigel
To select GPS as the default input port, it was required to tie PIN 39 (of

50-pin FPC connector) to GND.



-----------------------
Many thanks for the information, I was just coming to announce the same but you beat me to it, sure makes quite a difference knowing that:-)


I don't know if this was already common knowledge, or if it applies to any of the other Samsung versions, but I originally just used the information from the http://tipok.org.ua/node/53 web page and it isn't shown on the diagram there.



To be fair to the seller, they did try to tell me this when I first queried it not defaulting to GPS but a bit of linguistic confusion initially sent me off in the wrong direction.


All is fine now, with pin 39 grounded it does boot up into GPS mode, and there's no more amber Alarm light.
Aside from anything else the Alarm LED still functions as an over and under supply monitor though, which is a nice little bonus, and overall I'm now very happy with this unit, to the extent that I've even bought another one:-)



Mark,


Many thanks for your explanation of the LINK/EXT situation, I did assume it was related to a non GPS backup but was still intrigued at the possibility that the GPSDO itself might be fed with an external conditioning input, although I suspect that's highly unlikely



I don't know if it will help but I've logged the command set from this one and have also been logging some streamed data and will send that to you off list.


Nigel GM8PZR




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