Author Topic: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)  (Read 455184 times)

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Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #900 on: August 07, 2017, 08:01:36 pm »
There is a Trimble version on ebay sale for ~$60. The seller does not advertise it as a GPSDO, but rather a GPS OCXO.

He has several, so I was wondering if anyone has some incite? Worth the gamble? It looks a little crusty as in the can is flaking. I just recall reading here somewhere someone bought one that was not disciplining and that since it was labeled as just an OCXO that is nothing to complain about. I don't really want an OCXO for that price.
 

Offline texaspyro

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #901 on: August 07, 2017, 08:34:08 pm »
I bought a couple of $60 dollar units (don't remember the seller) and they worked fine.   YMMV...  there are a lot of damaged units out there that have parts broken off the boards.
 

Offline cdev

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #902 on: August 13, 2017, 07:11:02 pm »
Do all the symmetricom units have the same 50 pin header that the Trimble-Symmetricom "UCCM" device does?

A True Position GPSDO I recently got also has a very similar looking header. (actually two pairs of similar looking test points. See photos) Perhaps they mate with a test jig and are used during manufacturing or repair, or maybe they are a broadcast industry or telecom standard. Who knows?

I have not had the time to go through the pins yet. Need to clean up first. And need some time. My desk is such a mess its scary.




 
« Last Edit: August 13, 2017, 07:28:02 pm by cdev »
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Offline texaspyro

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #903 on: August 13, 2017, 07:27:48 pm »
Do all the symmetricom units have the same 50 pin header that the Trimble-Symmetricom "UCCM" device does?

A True Position GPSDO I recently got also has a very similar looking header.
 

No, the Trueposition devices do not have anything remotely like it.  I don't know what you think is a connector... all the connections are standard pin headers.

The Symmetricom devices have a flat cable header that was removed for that photo...
 

Offline cdev

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #904 on: August 13, 2017, 07:37:59 pm »

It looks like a card connector. Its on the opposite end from the crystal oven. There are two pairs of 50 pins each 

They are numbered such to lead one to think they were pins  "1 2" at the top,  and "99 100" at the bottom of each bank. So whatever pin header it has that connects to it, it has two of them, 100 pins each.

They must use pogo pins or similar and clamp on..

Quote from: texaspyro on Today at 13:27:48>Quote from: cdev on Today at 13:11:02
Do all the symmetricom units have the same 50 pin header that the Trimble-Symmetricom "UCCM" device does?

A True Position GPSDO I recently got also has a very similar looking header.
 

No, the Trueposition devices do not have anything remotely like it.  I don't know what you think is a connector... all the connections are standard pin headers.

The Symmetricom devices have a flat cable header that was removed for that photo...
"What the large print giveth, the small print taketh away."
 

Offline Bryan

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #905 on: August 13, 2017, 07:40:51 pm »
Did you have  a look here. http://tipok.org.ua/node/53

-=Bryan=-
 

Offline TheSteve

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #906 on: August 13, 2017, 07:44:01 pm »
Do all the symmetricom units have the same 50 pin header that the Trimble-Symmetricom "UCCM" device does?

All of the UCCM units have that connector(it was removed in the linked pics) and it was used to connect to the cellular base station equipment they were removed from.
VE7FM
 

Offline cdev

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #907 on: August 13, 2017, 09:26:03 pm »
Why not use the RPI as your NTP server? The USB-Ethernet problem? They have greatly reduced the jitter from that by setting the low latency flag via setserial.

David Taylor has info on his satsignal.eu site about how PPS over a USB-to-UART adapter compares to real PPS using a serial port or GPIO.  (But its Windows-specific)

If somebody has no serial port and no GPIOs,  USB may be their only option.

The link above has lots of info.

People can use a pair of resistors as a voltage divider so that RPI GPIOs and UARTs, etc. are not fed 5 volts, if your GPSDO outputs 5 volts..


Quote from: texaspyro on 2017-01-16, 02:36:40>Quote from: edpalmer42 on 2017-01-16, 00:25:28
The best NTPD performance is obtained by having the 1 PPS on one of the RS-232 control leads.  The Tbolt doesn't do this unless you do the hardware mod yourself, but other GPSDOs do.  If LH doesn't pass that on to its virtual port, NTPD will only have the ASCII to work from and won't provide its best performance.

You would just wire the 1PPS signal from the receiver to whatever pin your NTP expects.  For 1PPS in via the serial port (the standard pin used by NTP is the carrier detect line) you would wire the 1PPS signal to the the virtual com port connector CD pin.  Heather passes the data stream from the receiver through to the virtual com port which then feeds NTP.

For the serial data the flow is RCVR -> HEATHER RCVR PORT -> HEATHER VIRTUAL PORT -> NTP
For the 1PPS signal it is RCVR -> VIRTUAL PORT CONNECTOR CD pin-> NTP

If you are using a receiver that NTP understands, you could do much the same thing with just a serial "Y" cable and send the receiver serial output signal to both the Heather serial port and the NTP serial port.   But if you are using something like the UCCM receivers that NTP doesn't know about and that only send the time out every other second, Heather can generate a NMEA stream to feed NTP.

My intended configuration is to have a Raspberry PI with the 800x480 touchscreen controlling and monitoring the receiver and spitting out a NMEA stream and 1PPS for feeding NTP.



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Offline texaspyro

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #908 on: August 13, 2017, 10:28:50 pm »

It looks like a card connector. Its on the opposite end from the crystal oven. There are two pairs of 50 pins each 

They are numbered such to lead one to think they were pins  "1 2" at the top,  and "99 100" at the bottom of each bank. So whatever pin header it has that connects to it, it has two of them, 100 pins each.


Weird,  they are not on any of my boards... I have two different types of the Trueposition GPSDO.  I suspect they are not used by whatever equipment they came out of and never had connectors soldered on.  Later revisions of the card probably ditched the connectors.
 

Offline cdev

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #909 on: August 14, 2017, 01:36:36 am »
I think maybe I used the wrong phrases. My card looks just like the one in the PDF file.

Here I highlighted the areas that I am too exhausted to probe now. They probably contain more signals - some may be of interest, perhaps. Or at least monitor-able parameters.

I'm too exhausted to take a probe to it now, it needs to be done while its on, and in my current exhausted state on my messy desk, I would probably zap something.

These kinds of situations are why I really want to make some kind of probe position-er.

"Unsteady hands make Devil's oscilloscope"!



Quote from: texaspyro on Today at 16:28:50>Quote from: cdev on Today at 13:37:59

It looks like a card connector. Its on the opposite end from the crystal oven. There are two pairs of 50 pins each 

They are numbered such to lead one to think they were pins  "1 2" at the top,  and "99 100" at the bottom of each bank. So whatever pin header it has that connects to it, it has two of them, 100 pins each.


Weird,  they are not on any of my boards... I have two different types of the Trueposition GPSDO.  I suspect they are not used by whatever equipment they came out of and never had connectors soldered on.  Later revisions of the card probably ditched the connectors.
"What the large print giveth, the small print taketh away."
 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #910 on: August 17, 2017, 08:39:35 pm »
I have received the Trimble version of this reference, with all of the work already done to build it into an enclosure (similar to the BG7TBL).

I have not been able to figure out the data communication. (I posted previously here initially just being confused about basic serial comms: https://www.eevblog.com/forum/beginners/rs232-rx-vs-tx/)

What I think the builder has done (he uses the 50-pin ribbon cable exclusively) is to route the Trimble's debugging serial port pin 37 Tx to a feedthrough cap, then to a Sipex RS232 level converter chip, then to another feedthrough cap, and then back into the usual communication port pin 33 Rx. The same routing happens with the sibling Rx/Tx ports.

What's interesting is that the RS232 data right out of the Sipex chip looks like normal data you'd expect (TxD (57600 8N1) binary protocol, each 2 seconds bytes that seen as on "TOD EN" command are sent using this port. It's duration is 8ms every second with ±5V levels), but after the cap all of the the signal edges turn into very short pulses (±5V levels) on pin 33 Rx. Those pulses appear on the device RS232 RX pin interface connector as well as Trimble's J5 pin 1 Rx. The TX pin is -5V at J5 pin2 and on the device RS232 Tx pin. So something is happening through that cap or signals on the Trimble board are working to cancel each other out.

The LEDs on the Trimble unit blink mostly as described earlier in this thread, with the ACT and ALM leds briefly red on power-up, then the ACT goes steady green, then starts slow flashing (I see it more as toggling between red and green). If I press the MACT button the ACT led will flash quickly for maybe 20 seconds, then start flashing slow again. I think it's trying to lock. If I leave it long enough, the ACT led will flash quickly, and I think that means it's locked.


My main question now is how should I proceed to try and get communications working and figure out if the unit is really locking? I have considered unsoldering the feedthrough caps connected to pins 33/34 Rx/Tx or perhaps removing the Trimble unit entirely from the builders board and interfacing with J5. But I am wondering about the -5V on the Trimble's Tx pin. Does the Trimble usually transmit or does/can it be configured to not transmit unless commanded to do so? I'm certain I am going to have to disconnect something to remove those pulses from the Rx pins before I can send anything to it.

Thanks
 

Offline pigrew

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #911 on: August 17, 2017, 09:37:12 pm »
My main question now is how should I proceed to try and get communications working and figure out if the unit is really locking? I have considered unsoldering the feedthrough caps connected to pins 33/34 Rx/Tx or perhaps removing the Trimble unit entirely from the builders board and interfacing with J5. But I am wondering about the -5V on the Trimble's Tx pin. Does the Trimble usually transmit or does/can it be configured to not transmit unless commanded to do so? I'm certain I am going to have to disconnect something to remove those pulses from the Rx pins before I can send anything to it.

I recently got a Trimble UCCM module (though not the one nicely packaged; I have only the board). I soldered wires for +5.5V and GND to the board (+5.5 to the fuse near the long FFC conector, and GND to the GND of a RF connector on the bottom of the board). Then, I installed  1x5 0.1in pitch male header at J5. I use J5 to communicate with the board. It uses +/-5 V at 57600/8N1. I connected it to a USB RS232 converter (RS232-level, NOT TTL/3.3V logic) by using female-female dupont-style connectors. PIN1 goes to DB9#3, PIN2 goes to DB9#2, Pin4(gnd) goes to DB9#5. +/-5 is within spec for RS232 levels.

I don't know what happened to your board. Perhaps they accidentally loaded capacitors instead of resistors?

I can communicate with it with putty (terminal emulator), and with Lady Heather. It won't output anything by default. You have to give it a newline to get a command prompt, or enable the PPS messages with "TOD EN" to get it to automatically output something. As provided, it was in position hold mode. You have to tell it to do a factory reset (SYST:PRES) to get it back into 3D tracking/survey mode.

For Lady Heather, you'll have to edit your configuration file. For COM11, I set the parameters (on Windows) of "-11  -br=57600:8:N:1 -rxC -tz=EST5EDT".

Unfortunately, my module seemed VERY deaf. It usually receives only 2-4 channels at a time (with the elevation mask set to 5). It went into holdover fairly often. Other similar-aged modules receive 6-8 channels with the same antenna in the same location with the same cables.
 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #912 on: August 17, 2017, 10:38:00 pm »
OK, I'll give that a shot.

It's odd that there are signals on the Rx line though. The guy has other positive feedback on the device so I thought he might have misloaded something.

 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #913 on: August 18, 2017, 12:59:21 am »
Still not working. Pin 5 is supposed to be ground, right? I get lots of AC noise on the Rx/Tx lines on my scope if I use pin 5 as ground.

Is there any sane reason to connect a Sipex chip between the two UARTS on this board?

I'm about to break out my soldering iron, but am worried that I'll find out that I've destroyed capacitors and ripped traces off a perfectly sound design just because I don't know what I'm doing...
 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #914 on: August 19, 2017, 12:51:16 am »
All, the seller has sent a replacement unit and I have it connected. LH saw it right away and now it is reporting a status of "Settling". This is exciting!!!
 

Offline texaspyro

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #915 on: August 19, 2017, 01:16:17 am »
All, the seller has sent a replacement unit and I have it connected. LH saw it right away and now it is reporting a status of "Settling". This is exciting!!!

Wee-wee down your leg exciting? 
 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #916 on: August 19, 2017, 10:30:07 am »
We are now seeing the status toggle between locked and recovering...not sure why it's reporting that. 5 to 7 sv's green. I started a survey.
 

Offline TiN

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #917 on: August 19, 2017, 12:15:55 pm »
Looks like footprint for some high-density B2B connector, like Samtec BSH.
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Offline cdev

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #918 on: August 19, 2017, 12:48:00 pm »
So is your antenna outdoors and seeing lots of sky sans trees or wires or dogs or blogs or tall buildings or what have you?

If not, expect some degradations in performance.

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Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #919 on: August 19, 2017, 05:22:07 pm »
Nine green SV's, I guess  the survey completed OK. LH stopped upping the % at 99% and then it went back to Position Hold mode, operation mode stays Locked, PLL went Lock, and TFOM was 2.
 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #920 on: September 06, 2017, 06:00:56 am »
Hey all. One of my UCCM boards is not reporting OSC data (stuck at 0.000) and the PLL stays at INIT. I do get DAC and PPS values, however. Do all of these units self report OSC and PLL lock status? This one has much older firmware, in the v1.x range. I'm wondering if this could be a hardware issue or firmware just not supporting the feature?
« Last Edit: September 06, 2017, 06:24:24 am by metrologist »
 

Offline Briain

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #921 on: November 14, 2017, 02:55:58 pm »
Hi folks

Firstly, my first post must begin with a huge thank you to all the contributors to this excellent and fascinating thread, and atop that, a particularly mega-huge thank you to texaspyro for the wonderful LH!!

Pictured below is my recently installed Trimble 57860-20 GPS Bullet antenna (no expense spared on the Shakespear S/S poles, but the weather here can get really quite vicious) and the view behind it (looking to the north) shows part of Edinburgh (Scotland) with the a small section of the River Forth (just visible) and the Fife hills visible in the background. (Edit: I just noticed that the blurry thing to the right of the lower U bolt is actually Edinburgh castle; sorry about the poor image quality, but to be honest, it really is rather a tedious building, so it's best seen from a half-decent distance.)



Below shows a screen-shot from LH with the GPSDO's elevation mask temporarily set at 0 deg (just to obtain a picture of what it could see). I planned it all to give me a 20 deg clearance (and the elevation mask now set to 20 deg) and other than some pesky trees to my east (fetch me a chainsaw, immediately) I pretty much achieved my goal.



I'm currently building a linear regulated multi-rail PSU for my recently procured Trimble Thunderpants, so I will soon have two units permanently installed and running, so I'm now another one who has been fully infected by the GPSDO bug!

Once again, a huge thank you to all concerned!   :)

Bri (GM8PKL)
« Last Edit: November 14, 2017, 08:51:47 pm by Briain »
 

Offline Briain

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #922 on: November 14, 2017, 03:09:52 pm »
Hey all. One of my UCCM boards is not reporting OSC data (stuck at 0.000) and the PLL stays at INIT. I do get DAC and PPS values, however. Do all of these units self report OSC and PLL lock status? This one has much older firmware, in the v1.x range. I'm wondering if this could be a hardware issue or firmware just not supporting the feature?

Hi metrologist

I have one of the Trimble UCCM boards on loan (from another forum member, GM8BJF) and I am aware that he had an issue with the antenna power feed and comms, so I believe that he picked up 5V from elsewhere to feed the antenna and it all then sprung into life, but this also one displays the same outputs (on LH) as you have described in your post (and in addition, after power up you have to press the MACT button to get the 10 MHz output, but it is actually locked). To check it, I have compared its 10 MHz to a fully functional Symmetricom (also borrowed from GM8BJF) and despite these odd conditions, the Trimble oscillator does appear to be fully 'under the whip' (I looked at the two waveforms on a 'scope and they remained perfectly in step over several days).

We had assumed the odd readings on LH were due to the antenna feed modification (and the Trimble thinking there was an antenna issue), so perhaps your results are related to a vaguely similar antenna communications related problem (though not to the extent that you had to arrange a 5V feed to it)?

I guess it could be down to a very early firmware build, but I have read the entire thread and from memory, I don't think that I've seen any other similar posts (which you'd expect to see if it was a firmware build issue) but I'll look at 'mine' very soon and report back with the F/W version installed on it; the unit is running in my cellar - a nice stable environment - and the Raspberry Pi it normally interfaces to is being temporarily used elsewhere, but it will be replaced very soon.

Bri
« Last Edit: November 15, 2017, 08:51:57 am by Briain »
 

Offline metrologist

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #923 on: November 14, 2017, 05:47:59 pm »
Thanks Briain.

Functionally it seems OK. Comparing two units on the scope, I think I recall the units would start to deviate about 180 degrees, as if one went into a tuning routine. Over several hours they would appear locked, but by morning I would notice the separation by leaving my scope on infinite persistence. Once I caught them drifting apart, it looked like one would tune end-to-end and then return to lock.

I don't have any real good equipment (probably more limited by my ability right now) to measure the stability other than that method. I was thinking of clocking the two referenced to a free-running OCXO.
 

Offline Briain

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Re: A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)
« Reply #924 on: November 14, 2017, 07:05:58 pm »
Hi

It's interesting that what you described so closely echoes what my own (err; I mean my loan) one also displays via LH (see attached screen-shot) so that's why I was wondering if the 'fault' might be based on a vaguely related issue (and also perhaps be largely irrelevant)? Before I received this unit, GM8BJF had it running - alongside a Simmetricom unit - into a dual channel 'scope, and it all looked pretty darned good, so after sparking it all up here, that is exactly what I did, and after a few hours of settling time, the two traces remained 'visually locked' (over a several day period) so despite all of the mildly concerning 'alarms' displayed from both the serial terminal outputs and the LH screen, it does appear to all be working just as it should.

Bri

PS I've just recovered the R Pi from its other nefarious duties, but after just consuming a bottle of Finca Carelio (which is 14.5% ABV, by the way) I think that it might be wise to not scrabble about in my cellar of particularly sharp and dangerously pointy things, right at the moment, but despite these dangers (and my great age) I will attempt to do so in the morning, and then - assuming that I survive the ordeal - I'll report back about the F/W, just as promised (and if not, you'll likely read of my untimely demise in the local newspapers; please do feel free to LOL).  ;D
« Last Edit: November 14, 2017, 07:16:51 pm by Briain »
 


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