A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)

[NivagSwerdna]

OK... I'm on to unit#2...

Hooked up to my TTi EL302RD supply and set to 5V 2A... when I turn it on I get... 3.27v and 1.25A with the CC lit...  on the output of the squealing TI boost converter I get 9V.

What's all that about then?  Sounds like I've fallen into a trap for young players?

After a while the squealing dies down and the OCXO is nicely warm and the power supply goes to 5V 770mA and CC goes out.

Fingers crossed

[Vgkid]

Sounds like what both of mine do.

[NivagSwerdna]

Sounds like what both of mine do.

Do you know why my Power supply goes into CC mode?  It should be able to deliver up to 2A @ 5V?  Is it something to do with inductive loads?

[Vgkid]

Can your psu go above 2A, i think mine might take about 2.2A

[NivagSwerdna]

Can your psu go above 2A, i think mine might take about 2.2A

"The EL302RD has two independent and isolated outputs each with a 0
to 30V, 0 to 2A capability and its own on-off switch. The outputs can
be wired in either series or parallel to provide voltages up to 60 volts
or currents up to 4 amps."

It's rated as dual 0-2A 0-30V.  I might try them in parallel and see what happens... it appears you can do that and get up to 4A.

[hs3]

Hooked up to my TTi EL302RD supply and set to 5V 2A... when I turn it on I get... 3.27v and 1.25A with the CC lit...

I have just tested with EL302D. Set to 6V and 2A. I get the same behavior that you described above. I also tried paralleling the outputs but no improvement.

This is with the same Symmetricom unit that works with Rigol DP832 set to 6V 3A as discussed couple pages earlier.

So it doesn't seem to be suitable load for the EL302D supplies.

There is probably a reason why the fuse at the input is 10A on the Symmetricom module.

[NivagSwerdna]

Interesting.

When I was powering from 2 supplies... 5V @ 250mA and 12V @ 500mA during warm up the total was around 7.25W or equiv of 1.45A @ 5V.
Even with inefficiency of the DC-DC converter that should be under 2A @ 5V.  I think the EL302RD just isn't oommpfy enough.

By the way...

UCCM-P > SYSTem:STATus?
-------------------------------------------------------------------------------
090-03861-03   serial number W560935175   firmware ver 1.0.0.2-01     LINK mode
-------------------------------------------------------------------------------
Reference Status __________________________   Reference Outputs _______________
   Ref 8KHz 0: [LOS]
                                              TFOM     2             FFOM     0
                                              UCCM-P Status[ACTIVE]

>> GPS: [phase:  1.77e-08]
ACQUISITION ................................................ [ GPS 1PPS Valid ]
Tracking: 6 ____   Not Tracking: 4 ________   Time ____________________________
PRN  El  Az  C/N   PRN  El  Az                GPS      01:57:23     19 MAR 2016
 10  29  52   42     1  51 274                GPS      Synchronized to UTC
 11  67 280   34     3  16 214                ANT DLY  +0.000E+00
 14  29  90   34     8  62 161                Position ________________________
 22  62 186   31    32  31  97                MODE     Hold
 27  31 143   35
 28  27 311   36                              LAT      N  51:**:**.***
                                              LON      W   0:**:**.***
                                              HGT               +10.90 m  (MSL)




ELEV MASK  5 deg
-------------------------------------------------------------------------------

Command Complete
UCCM-P >


We have lift off!  Just need to know how to route the LEDs to the front panel now and maybe do some serial interfacing for an LCD showing FFOM to front panel.

[davebb]

That's good news,was it your missing cap,
Dave

[NivagSwerdna]

That's good news,was it your missing cap,
Dave

No.  I gave up on that unit and it is on its way back to China. 

I bought another and although that had one missing cap, it was easily fixed and working now.   

I think the original had some big issues, certainly wasted a huge amount of my time.

I'm now plotting what to do with the interface.  I'm tempted to add an Arduino based front-end to display FFOM etc on a front panel, but really I should do the LEDs first.

Does anyone actually know the meaning of the 5 LEDs on the board?

[davebb]

Hi others have put some info on the LEDs on the 1page ,
I may fit 4 LEDs but 2 will tell you its good the green for lock
And the red for 1pps,

So you had to send the unit back to China, what was the cost of that ,has he given you a refund or do you have to wait for him to receive it
Dave

[NivagSwerdna]

So you had to send the unit back to China, what was the cost of that ,has he given you a refund or do you have to wait for him to receive it

That's a work in progress.  Under Paypal/EBAY Buyer protection if item is "Not As Described" then Seller has to pay return postage and offer refund (although they might try and convince you otherwise).

[grumpydoc]

Hi yes you have a bad unit , fly seller will tell you he will send another one but he will not send,tell him you want a refund, open a case with ebay, he asked me to close the case I opened as he said  he had sent another one,
I did not close the case, and ebay refunded me from his account , and the replacement unit never did arrive ,
still I did get the broken one working, as I put on a new u25 inverter chip and caps
Dave

Looks like he does this regularly as he promised me a replacement and nothing has shown up. I wouldn't mind if he had actually sold them as "parts or repair". Looks like I will need to put it through ebay.

Now that I look carefully at the pictures C1 is loose in the sellers photos.

The bottom line, I suppose is, if you buy one of these, expect to have to do some repair work.

[Macbeth]

Same here. He asks to send it back. Once you tell him the full cost of tracked and that he has to pay for it he's not happy, so will then pretend to ship a new one out to you. Don't waste your time. Better to just buy another one and then claim the older one as a dud on ebay and use it for repair parts, because you will definitely need them! 

[davebb]

Hi have you seen from a post on here there is a UK seller selling these for the same price, don't know if they are sent in the UK?
Dave

[Bryan]

GPS- Display working 

Is there a link you can share to the project.

Here everything is already described.

Ok, think I found it.
 
http://www.f4ctz.fr/?lang=en

If I understand what others have/are doing they are taking the TX off the GPC receiver circuitry, not the RS232 header circuitry and it outputs a data stream in NMEA format so the above project can read, decipher and display on the LCD?

The reason I ask is there is a  number of Arduino libraries that can read/interpret NMEA data streams.

Hi

The "good stuff" is not in standard NMEA strings. It's in NMEA format proprietary messages or in other even less easy to interpret strings. .

Bob

If you cut into the connections on the RX and TX on the GPS module, you can do a lot of things. The normal "timing info" port does not allow you to do variable NMEA.

No need to cut anything.  You can just listen in pin 3 TX, pin 4 RX and pin 5 1PPS.

From GPSDO to GPS I have seen examples of these commands (not in this order or frequency)...

$PFEC,GPint,GGA01
$PFEC,GPint,GSA01
$PFEC,GPint,GSV00
$PFEC,GPint,VTG00
$PFEC,GPint,ZDA00
$PFEC,GPint,acc00
$PFEC,GPint,anc00
$PFEC,GPint,anc00,acc00
$PFEC,GPint,rrm01
$PFEC,GPint,tps01
$PFEC,GPint,tst00
$PFEC,GPrrq
$PFEC,GPrrs,1,100,1
$PFEC,GPset,M05
$PFEC,GPset,U00000000
$PFEC,GPset,Z1
$PFEC,GPset,t-000080
$PFEC,GPsrq

on the output side I see...

$GPGGA
$GPGSV
various
$PFEC
e.g.
$PFEC,GPacc,XXXXXX0XXXXXXXXXXXX00XXXXX0XXXXX
$PFEC,GPacc,XXXXXXXXXXXXXXXXXXX00XXXXX0XXXXX
$PFEC,GPanc,800106000000,00000000002000000002200000200000
$PFEC,GPanc,800106000000,00000020002220000002200000200000
$PFEC,GPanc,800106000000,00000020002222200002200000200000
$PFEC,GPanc,800106000000,00000020002222222002200000200000
$PFEC,GPrrm,2,2,00,00,00,00,+000,+00
$PFEC,GPtps,160315224627,2,0,1,000000000000,00,00,000000000000,1888,254787
$PFEC,GPtst,0,4850266005,1,C

Steady state (in survey mode at least) is for 1 Hz output looking something like...

$PFEC,GPtps,160315233257,1,0,1,150701000000,00,17,160315231107,1888,257594
$PFEC,GPrrm,2,2,00,00,00,00,+000,+00
$GPGGA,233258,****.3935,N,*****.4444,W,0,00,00.00,000005.1,M,0046.9,M,,
$GPGSA,A,1,,,,,,,,,,,,,00.00,00.00,00.00

I doubt anyone will find that very interesting.   

The protocol spec is here http://www.ko4bb.com/getsimple/index.php?id=download&file=02_GPS_Timing/Furuno/Furuno_GT8031_Protocol_Specification_Rev1.pdf

Monitoring the output of the GPS tx pin and it is returning similar data. Advantage of the output format vs the serial output is it would be easier to process using the comma delimiters. Goal is to output some of the useful data onto a LCD or OLED screen from a Arduino project. Similar to the other project that has been referenced.

[NivagSwerdna]

Monitoring the output of the GPS tx pin and it is returning similar data. Advantage of the output format vs the serial output is it would be easier to process using the comma delimiters. Goal is to output some of the useful data onto a LCD or OLED screen from a Arduino project. Similar to the other project that has been referenced.

We should join forces.  The really interesting stuff is the SCPI ('skippy') on the main serial connection as that includes the FFOM and timing loop info.  The NMEA on the receiver will give you position and time, the position will be fixed for me so that isn't hugely interesting.  The time from the NMEA is always behind actual time, so if you are happy with a time that is 500mS late (and may or may not have been adjusted for GPS versus UTC) that might be OK, you can always use the PPS signal to adjust the edge back.
I haven't yet decided whether to use an Arduino clone (since they are so cheap) or to use a Raspberry Pi and just make it into an NTP server too.  I quite like the idea of these two since it could an open source solution and easily reproducible.  Haven't decided on a display yet... will probably go for a simple 16x2 LCD.

[davebb]

Hi I talked to Dan about the led and it is a bug he thinks it may go off when the survey has Finnished
Dave

[SHF]

Hi I talked to Dan about the led and it is a bug he thinks it may go off when the survey has Finnished
Dave

OK, thanks

[bseishen]

Created a 3d printed mounting plate if anyone wants to use it. Its just a plate with standoffs. Uses m3 screws to hold the GPSDO down.

[Bryan]

Monitoring the output of the GPS tx pin and it is returning similar data. Advantage of the output format vs the serial output is it would be easier to process using the comma delimiters. Goal is to output some of the useful data onto a LCD or OLED screen from a Arduino project. Similar to the other project that has been referenced.

We should join forces.  The really interesting stuff is the SCPI ('skippy') on the main serial connection as that includes the FFOM and timing loop info.  The NMEA on the receiver will give you position and time, the position will be fixed for me so that isn't hugely interesting.  The time from the NMEA is always behind actual time, so if you are happy with a time that is 500mS late (and may or may not have been adjusted for GPS versus UTC) that might be OK, you can always use the PPS signal to adjust the edge back.
I haven't yet decided whether to use an Arduino clone (since they are so cheap) or to use a Raspberry Pi and just make it into an NTP server too.  I quite like the idea of these two since it could an open source solution and easily reproducible.  Haven't decided on a display yet... will probably go for a simple 16x2 LCD.

I am the same, not very interested in the GPS coordinates, but want to know the phase and frequency differences, how many satellites, timing etc. I would like to use a OLED vs a LCD.

http://cyaninfinite.com/tutorials/interfacing-0-96-oled-display-with-arduino-uno

There is a number of Arduino libraries that can interpret NMEA strings, shouldn't be too hard too implement to extract the data that I need. I am sure you have seen the pdf on the NMEA commands that the receiver should support. Was going to try later this weekend and see if I can successfully send the GPS the commands through the receiver and see what it returns. Should be able to get some of the timing information.

[gm8bjf]

Hi have you seen from a post on here there is a UK seller selling these for the same price, don't know if they are sent in the UK?
Dave

I have had a couple from the UK seller. The first one was fine, just needed an SMD cap in the RS232 interface replacing. The second one has been more problematic and I am awaiting a replacement. The seller seems good and volunteered a replacement right away. The boards seem to come from the same source in the Far East as the second one I got had the "oilyness" and more loose/missing parts. However at the price they are not too bad. Mine both had their last loogged co-ordinates in Japan. I see on TaoBao.com they are about the equivalent of £16 !

Brian.

[guido]

Got a package from China today. Slammed some components on the PCB and did some first tests.



Not much to it, designed it with components from the stash. From left to right:
 - connector to LCD (two pins bigger than needed, but i had some flatcable with connector available)
 - pic 16F627A to read the UCCM and write to the LCD, specific xtal frequency to match the baudrates
 - DCDC regulator from 12V to 5V (customer specific version, but Fabrimex was very helpful).
 - RS232 level shifter (using the standard RX/TX header on the UCCM). Relay switches between pic and DB9.



This is the general idea; i am going to stack the PCBs. For testing the readout PCB is on top. I will swap later. The RS232 headers line up. Some resistors are just mounted temporary, as i need to change them later to adjust the brightness of the final LEDs.



It worked in one go  Note the software was written for a 16x2 display untill now. This is why the bottom half on the display is not initialized. This display is two times a 40x2 display, with separate enable lines.

The text is coming from the UCCM (no antenna connected). So reading and writing (i'm switching to 9600 baud) works. And writing to the LCD obviously works.

Now it is only a matter of software to read the various strings from the UCCM and writing them on the display. Got enough space 
This will take a while, not much time at the moment. And then putting it all in a nice enclosure.

[Vgkid]

Nice job  .

[NivagSwerdna]

I see you have 4 LEDs.  Please can you show how/where you are attaching these.

Have you left the old SMD LEDs on the board?

[f1rmb]

Hi,

I see you have 4 LEDs.  Please can you show how/where you are attaching these.

Have you left the old SMD LEDs on the board?

Personally, I've unsoldered the leds and connect new ones on the frontplate:

https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-%28ocxo-furuno-receiver%29/msg823156/#msg823156


Cheers.
---
Daniel