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 who’s GPS chipset is being used, a fix might be possible. I’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 receiver’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 <time-nuts@lists.febo.com>
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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