[time-nuts] Motorola Oncore UT+ firmware upgrade & backup power questions

Pete Stephenson pete at heypete.com
Fri Mar 13 16:33:48 EDT 2015

Hi all,

After a few years of using a Garmin GPS 18x LVC for timekeeping, my
budget now allows for some upgrades and I had a small field day on eBay:
I acquired a Trimble Thunderbolt, two Trimble Resolution Ts, and two
Motorola Oncore UT+s (seconds purchased for spares and testing).

The documentation for the Trimbles is clear, but I had several questions
regarding the Oncores that I was unable to find clear answers to online.
I would be very much obliged if the folks here might be able to help.

1. Is it possible to upgrade the firmware on the Oncore UT+? If so,
where can one acquire the latest firmware (3.2, I believe) files and how
would go one about installing it? Is this something WinOncore can do? I
ask because the receivers on eBay are of varying vintage and may not be
fully upgraded.

Since Motorola exited the GPS business a relatively long time ago,
firmware updates and directions have proven difficult (impossible so
far) for me to find.

2. The two Oncores I purchased were not factory-equipped with a
rechargeable battery. The user guide says that one can apply "Externally
applied backup power (< +5V)" to pin #1 in order to maintain data in RAM
in case the main power is interrupted.

Can one use a common non-rechargeable coin-cell battery like a CR2032 to
provide this backup power, or does it need to be a rechargeable battery?
Will a CR2032 or the Oncore itself be damaged if such a cell is used?

3. Tom says at
<http://lists.ntp.org/pipermail/questions/2012-October/034001.html> that
in addition to being an input for external backup power, pin #1 on the
Oncore provides current-limited 5V for battery/supercapacitor charging.

Is this true for Oncore receivers that were not factory-equipped with a
rechargeable battery? If true, what is the maximum current that can be
safely supplied by the pin? As above, is it safe to use a
non-rechargeable battery like a CR2032?

If pin #1 can supply power and I wanted to charge a supercapacitor from
that pin, would I also need to include a current-limiting resistor to
prevent the Oncore from sourcing too much current?

I could find nothing in the user guide that says that pin #1 can be used
for charging a battery.
is unclear on whether or not pin #1 can be used for charging batteries,
or if it's safe to use non-rechargeable cells like a CR2032 coin-cell
4. The user manual and the battery backup considerations document says
that the Oncore UT+ draws 5-100 uA (15uA typical) from the backup power
source. Is this a constant draw, even when the main 5V power is being
supplied to the unit, or does the unit only draw current from the
battery when the main power is interrupted?

I'd measure it directly, but none of my multimeters are able to
accurately measure microamperes.

Thank you all for your time and assistance. If any other time-nuts
happen to make it to Bern, Switzerland in the next few years, please let
me know and drinks are on me.


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