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

[Vgkid]

Looks like both modules work(at least power on correctly), need to order some mcx to sma connectors.

[davebb]

That's good news
Dave

[guido]

Took an old pic (16F627A) out of the stash and hooked it up with a MAX232 to the serial port. And connected an LCD.
The port we are talking to is serial2. Got the basics working using a 3.6864MHz xtal (get an exact baudrate).
I'm becoming old fart, so no arduino Just MPLAB, assembly and an USBEE for debugging.

For now i'm sending a command string and then dump the response on the LCD until a Carriage Return occurs. Since the GPS also replies the command string (echo), i'm only starting after the LF of the command string has passed. Took some tweaking, but it works now.

So "sync:ffom?" to the UCCM and e.g. "PLL stabilized" on the LCD.

Since i'm writing each received byte individually to the LCD after reception, i had to slow down the UCCM.
Switched it to 9600 baud. You can use only capitals: SYST:COMM:SER2:BAUD 9600.

I'm planning on using a 4 line LCD to display some interesting status lines.

[Macbeth]

Switched it to 9600 baud. You can use only capitals: SYST:COMM:SER2:BAUD 9600.

Are you using 8,N,1 ? I can certainly use lower case with mine. With the baud rate I quickly found I had to issue that SYST:COMM:SER2 command to drop it from 57600 default to 19200 instead as otherwise I get a lot of ascii corruption. This could just be the crappy CH340 USB adaptor and equally crappy hub I am using on my PC though 

[Vgkid]

What is the current draw of your units, one takes about 2.2A, while the other takes 2.6A. I think thst one might have an unhappy dc/dc converter. Its inductor gets pretty hot, when it(ocxo) is warming up.

[guido]

Should have said "only the capitals". So you can use "SYST:COMM:SER2:BAUD 9600" instead of "SYSTem:COMMunication:SERial1:BAUD 9600". So less characters to send to the unit.

Communication works fine, either with the pic or with my pc (pentium with win98 and putty ). The only problem i had was that there was not enough time to write a character to the LCD (too lazy to first buffer the string in an array, i'm just writing a received character to the display). So switch the unit to 9600 and there is time enough for that (i'm using interrupts, so it was not a receiver buffer overflow, but i was still writing on the display while a character was received and then already overwritten by the next one). Maybe i could have optimized the LCD routines, but this was also an option. Note the UCCM and pic must be powered at the same time; the pic assumes that the unit starts talking 57600. The UCCM does not remember a change to 9600 when powered off.

Now that the basics are working, it is only a matter of extracting the interesting data. E.g. issue POSSTAT and wait for "visible stat" and display the number behind it (until the CR). Same for "tracked".

I'll probably use LED:GPSLock? to read the status of the LED and use it to switch on a LED via the pic And make a button to switch to DIAG mode and back and maybe another one to switch the output on/off. That kind of stuff. See what goodies are availabe. Note i don't care about GPS time and position; i'm only in it for the 10MHz out in my 'lab'.

No idea about current; the step-up converter in mine was DOA. I'm now doing development without powering the OCXO.

[Nuno_pt]

Hi all,

I'm looking at this GPSDO also to put in my lab, but have a few questions:

What is the OCXO model?
It's worth to change it by an MV89A, since it's a Double OCXO?

It's only for the 10MHz, later will add an amplifier to split the signal to more equipment's,so for now no LCD.

[Vgkid]

51x40x19.,it predates the rakon acquisition of c-mac. So it could either be a c-mac or temex oscillator.

[guido]

You can see the OCXO number in the picture on the first page. Symmetricom part.

Had a look on the internet and found manuals for similar units. Tried a few extra commands (shown with answer):

• *TST?                                                                  +0
• SYST:ERR?                                                           +0,"No error"
• DIAGnostic:ROSCillator:EFControl:ABSolute?      +605912

I'll have another go at it to find the useful stuff.

Don't know how useful the first two test commands are, since i get no errors without antenna and +12V supply to the TCXO. I'll probably use the error request once at start-up.

And i got an LCD with 4 lines today at the local electronics shop (dump). 4x40 So more than enough space to display parameters.

[Vgkid]

You can see the OCXO number in the picture on the first page. Symmetricom .

Its closest equivalent is the Rakon ROX5242T2. The reason for going with rakon is in the model designator 'stp' which was used on both rakon and c-mac ocxo's.  Plus the datecode, frequency output"fo" are similiar.

[guido]

Copied all commands out of the manual of the HP5803B to try them (not all, skipped serial settings and firmware upgrade commands for obvious reasons). Found some more interesting commands:

DIAGnostic:LIFetime:COUNt?   value returned represents 3 hours in the HP, that would be nearly 4 years for mine

GPS:INITial:DATE 2016,1,29
GPS:INITial:TIME 23,59,01
GPS:INITial:POSition N,1,1,1,E,1,1,1,0  (not sure yet what the difference is with GPS:POSition)

you can set date/time and/or position to speed up the survey. I'm planning to use it only here in the lab, so i probably poke the coordinates of my house at startup 

Other stuff:
GPS:POSition:SURVey:PROGress?                     +0
SYNChronization:HOLDover:DURation?                  +0.00000E+00,0
SYNChronization:HOLDover:DURation:THReshold 123
SYNChronization:HOLDover:DURation:THReshold?         +123
SYNChronization:HOLDover:INITiate                  "Data corrupt or stale"
SYNChronization:IMMediate                        "Execution error"
*CLS
SYSTem:LANGuage?                              "INSTALL"
DIAGnostic:QUERy:RESPonse?                        +123

[edpalmer42]

And if you're really adventurous, try this command

SYST:LANG "PFORTH"

It likely won't work, but if it does, it'll put you into the pFORTH interpreter that's underneath HP's Z38xx series of GPSDOs.  A few people have experimented with it, but there's very little info on it.

To exit from the interpreter the command is apparently 'halt'. 

Ed

[davebb]

Hi today i was having a play as i just got a ftdi usb converter reddy for when i box the unit up
i just looked at
REFerence:TYPE?

and it was set to link, you can set it to GPS
WHAT should this be set to,should it be set to gps?
Thanks Dave

[guido]

Was also looking at this. Made some printouts when locked:

STATUS:
2-2. #Current Reference Type ----------- [LINK]
2-3. #Current Select Reference --------- [GPS 1PPS]
2-4. #Current Reference Status --------- [Ref Analyzing]

UCCM-P > sync:ref:enable?      GPS,LINK
UCCM-P > ref:type?         LINK

Since i have pll locked it seems not to matter that much. But i'll probably set this together with some other initial commands (initial location and 9600 baud). My assumption is that you can enable/disable GPS and LINK separately and ref type selects the primary. But i think that the other one is used as backup (so here GPS since there is no LINK connected). So i'll use:

REFerence:TYPE GPS
SYNChronization:REFerence:DISABLE LINK

But it seems to work fine without

I'm working on a pcb to control the UCCM (same size to put it under the unit) and drive a huge 40x4 display with status info. And then some buttons to enable/disable the output, force the output without lock etc. I'll make the oven 12V switchable (my DC to DC converter was DOA) and also the LCD backlight. So then i can switch it on for a while to achieve a decent gps lock and then switch on the oven one hour before usage or so. Save some energy while it is locking.

By the way, these alarms do something, so handy for the display:
ALARm:HARDware?     10MHz            (no 12V to the TCXO)
ALARm:OPERation?     Antenna Fail   (no GPS antenna)

[Nuno_pt]

guido, that's an interesting project.

[guido]

Currently in breadboard stage. Need to make my mind up what features i want and then see if i put it on vero board or make a pcb.

Currently i'm using junk box parts: 16F627A, MAX232 and i will probably use an I2C I/O chip for driving the LEDs (not enough pins on the pic). I now have room for two pushbuttons (i'm using pin change interrupt). That's output on/off and force output. So no third one to switch between 1 and 2 PPS. But i guess i won't use that ever. There will be a switch, which will switch on a relay. With that the RS232 is switchable between the pic and a DB9 connector. So i can still hook up a pc. i'll probably also use the relay to switch power to the pic and lcd. No use having it running while there is no communication to the unit.

Guess i could use an arduino but i have more than enough (acient) parts available to do the job. And i like coding in assembler 

[Nuno_pt]

An UNO or Mini should do the job, specially the Minii at around 2€.

I guess Date, Hour, GPS: Doing fix/Nº of Sat's, the deviation from 10MHz in ppm if possible, should be enough.

If one like more stuff that is meaningful (and the GPS provide it) like operating voltages, alarms, etc, it could be enter in an menu system, where one button would toggle trough the menus.   

[davebb]

Hi Has anyone come up with how to stop the unit from doing a survey after the power has been off
Thanks Dave

[Macbeth]

Hi Has anyone come up with how to stop the unit from doing a survey after the power has been off
Thanks Dave

Nope. But I think that GPS:INITial:POSition overrides the default that seems to be somewhere in Japan and thus speed up the survey at least.

There must be some command to actually save this kind of data into FLASH, but I haven't found it yet.

[davebb]

ok thanks
Thanks Dave

[guido]

An UNO or Mini should do the job, specially the Minii at around 2€.

I guess Date, Hour, GPS: Doing fix/Nº of Sat's, the deviation from 10MHz in ppm if possible, should be enough.

If one like more stuff that is meaningful (and the GPS provide it) like operating voltages, alarms, etc, it could be enter in an menu system, where one button would toggle trough the menus.

I know. But i have the parts and tools available. And i also already have the software routines from other projects (lcd, serial, i2c). So it is more or less copy/paste. Just the button handling is new (but working now).

As to deviation from 10Mhz...? I would think that the output it generates is 10Mhz for what the device is concerned. Slaved to GPS to be as close as possible. It won't be off and then displaying the error. What you have is the PLL status, which you want to be "PLL stabilized" so the 10MHz out is exact (it won't a 100% but you'll get into time nuttery teritory).

Don't need menu's, 4x40 is enough to dump all relevant data Paid just 10 euros by the way, NOS at the local electronics shop. Just add a separate red LED which switches on if one of the alarm strings is not "NONE" or the output is switched off by the device or the status of the lock led is "off' etc. To make it highly visible that something is wrong.

I tried the GPS:INITIAL:POS (with google maps coordinates), still takes quite some time. But i did not yet compare it to a normal situation. I'm using EZGPIB in serial mode to run some commands every few seconds and log them in a file.

What you can do, if the device is stationary, is to read the coordinates it shows and then program a small micro to just issue the INIT command at power up. No need for the save command. What should also help is to set time and date apperantly.

[davebb]

Hi guido
also the unit does monitor the current the TCXO is using, as when I got mine caps and ic u25  and tracks had broken, when I looked at the log record, it had logged a fault for wrong current reading from the tcxo,
Dave

[guido]

Yes. It is in the POSSTATUS printout at the bottom:

UCCM-P > posstatus
......
  Antenna Voltage: 4765 mV,  Antenna Current: 32 mA

[davebb]

Hi guido 
I don't mean the Antenna Current: 32 mA,
I Do mean the TCXO Current, as you said that you was going to switch it,
Dave

[guido]

Sorry i misunderstood. As for this status, it is easier to just look at the HW alarm (process a single line of text). In case there is no power, it says "10MHz".
I'll probably combine both alarms and show something if one or both are not "NONE". And turn on the red LED