The Z3801As that I have seen have the Motorola Oncore VP 6-channel
receiver which I think predates the UT+, and all have had the rollover
issue.
The problem with swapping in another unit is that unless it sufficiently
imitates the VP at startup, the Z3801A will throw an error and never get
to locked state.
Of course, many of the old units still work fine except for the rollover
providing a bogus date, and external software can easily correct that.
John
----
On 2/5/22 6:19 PM, Bill Beam wrote:
I do not know what Z3801 uses for GPS.
I have several Motorola UT+ GPS modules running.
Older ones with V2 firmware suffer 1024 week rollover failure.
My units with V3.2 and V3.1 do 1024 week rollover correctly.
If you are able to communicate with your device using Lady Heather
she will correct any rollover error and display correct date.
On Sat, 5 Feb 2022 16:36:15 -0500, John Ackermann N8UR wrote:
I think the problem with the Z3801 is that it expects to see specific
handshake things at startup, in Motorola binary protocol. Dropping in a
random GPS will result in a "No GPS" error.
John
----
On 2/5/22 12:44 PM, Keelan Lightfoot wrote:
Depending on whoG€™s GPS chipset is being used, a fix might be possible. IG€™ve
poked around inside the firmware of a number of
Trimble receivers (so far three generations of the 4000 series, and the Placer
series). Because the first week rollover occurred in 1999,
any receiver made close to that date already has logic to handle a week number
rollover. Finding this in the disassembled code is usually
easy because they simply add 1024 to the week number, which usually appears as
an add instruction with a 0x400 immediate operand.
changing a 0x400 to 0x800 will extend the receiverG€™s lifetime another 20
years. The most difficult part of this is figuring out the
processor used on the receiver, and figuring out how to get the patched
firmware back into the receiver.
- Keelan
On Feb 3, 2022, at 8:50 PM, Bill Beam via time-nuts <[email protected]>
wrote:
The date issue is a 1024 week rollover failure in the GPS receiver.
A fix is to replace the GPS receiver with one that does not have this problem.
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Bill Beam
NL7F
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