[time-nuts] Synergy-GPS SSR-6tru Problem Resolved

Art Sepin art at synergy-gps.com
Fri Jul 25 18:17:35 EDT 2014


Once in a while a mea culpa is required and we're posting it here so everyone understands our commitment to the users of Synergy's products. 

The Original Synergy Adaptor Board was designed to allow Motorola's newer 3 volt 12 channel M12+ to plug into an older 5 volt 8 channel UT+ slot. That product worked for hundreds of users over the years until (we found out through your personal aggravation and agony) the recent introduction of Synergy's SSR series of u-Blox based precision timing boards. 

To make sure that the Synergy UT+ Adaptor Board issue is put to bed properly we asked for an external, formal technical review of this product that was introduced fourteen years ago.

The reviewing engineer's first comments were "Ouch! This will not work."  And, "no, the SSR boards do not work the same as the M12 boards on the Synergy Adaptor Board". "The M12+ and M12M receivers have separate serial ports for the two functions (Receiver command RxD and DGPS RxD input) so it does not matter what you do with the RTCM port, pin 5 on UT+ connector and pin 8 on the M12+/M12M connector, if not in use with an M12x receiver."

"The SSR boards, however, had to combine the two serial data streams expected by the M12x navigation receivers into one because the u-Blox receiver modules only use one serial input port for both receiver commands and DGPS correction data. The Synergy Adaptor Boards use a simple gate combiner circuit that worked well when using the M12+ or M12M but left Synergy open to this problem when using an SSR. Both serial lines on the SSR board, pins 2 (Receiver RxD) and 8 (DGPS RxD) are pulled high on the SSR board so open pins are OK but they must not be grounded."

"The solution is for Synergy to make a UT+ Adaptor Board part number available to users who only want to test the features of SSR timing receivers."

That new SSR only Adaptor Board part number, which we'll have available in a few days, will remove R3 (4.7K) and R4 (6.8K) from the adapter board and the compatibility issue will be resolved. In the interim, other users can pull pin 5 of the UT+ connector high (+5V) as you did. 

We apologize for the confusion and frustration, Bob, and thank you for the valuable feedback!

Art Sepin

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Stewart
Sent: Thursday, July 24, 2014 11:27 AM
To: Tom Van Baak; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Synergy-GPS SSR-6tru Problem Resolved

Hi Tom,

I think that an offline conversation with Dusty Morris may have pointed out the root cause.  The SSR-6tru board uses 3V logic, but the Motorola Oncore boards use 5V.  So the Synergy M12 adapter has to do the level shifting to protect the receiver.  It does this for input signals by using a voltage divider composed of a 4.7K resistor on top  (for the 5V input) and a 6.8K resistor on the bottom to ground.  The center tap of these two resistors goes to the receiver.  Normally we would expect an open TTL pin to be a logic high.  But, in this case, an open pin to the 4.7K resistor on top leaves the 6.8K resistor to act as a pull-down on the receiver's input pin.  At least that's my speculation.  I'm no EE.


 From: Tom Van Baak <tvb at LeapSecond.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
Sent: Thursday, July 24, 2014 12:02 AM
Subject: Re: [time-nuts] Synergy-GPS SSR-6tru Problem Resolved

Hi Bob,

That's very good news. Thanks for following through on this issue.

Newcomers to the list should know that unlike many of the large corporations in the T&F business, Synergy has been hobbyist and time-nuts friendly since the beginning. I know a couple of us bought our first GPS receivers from Synergy in the mid-1990's. This was in the early days of GPS where we used Tom Clark's TAC h/w and SHOWTIME.EXE s/w, in the same way we use Trimble's Thunderbolt h/w and Mark/John's HEATHER.EXE s/w today.


----- Original Message ----- 
From: "Bob Stewart" <bob at evoria.net>
To: "Bob Stewart" <bob at evoria.net>; "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Wednesday, July 23, 2014 3:19 PM
Subject: Re: [time-nuts] Synergy-GPS SSR-6tru Problem Resolved

As a reminder, I received an SSR-6tru receiver from Synergy, along with their M12 adapter, which allows you to plug it into a slot for an Oncore GT+, UT+, or VP. I was unable to get the receiver to respond to any commands from the u-blox u-center software.

After a lot of troubleshooting, I discovered that pin-5, the "DGPS IN" pin, must be brought to a logic level high in order for this assembly to work. If it's low, apparently anything going into the board on the Rx line is simply sent back out on the Tx line and not passed to the receiver. I've never owned a GT+ or a VP, so I wasn't aware that a logic high was needed on this pin. The UT+ works just fine with this pin not connected.


time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

More information about the time-nuts mailing list