Jackson Labs LTE-Lite, User Manual

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LTE-Lite User Manual
26 © 2020 Jackson Labs Technologies, Inc.
$[JLT Proprietary Status String ID],[filtered UTC offset in ns], [raw UTC offset in ns], [number of
captured 1PPS pulses], [lock status], [EFC voltage], [EFC percentage (0% to 100%)], [estimated
frequency accuracy (similar to 100s ADEV)], [seconds in holdover], [number of Sats tracked (<9)],
[health status]*[NMEA compatible checksum]
N.B: Please note that from time to time this serial port will have short binary messages on it
which are routed to the internal GPS receiver. It is thus recommended that any parser using
the output from this serial port only parses sentences beginning with a valid ‘$’ character, and
that a parser also checks the NMEA checksum at the end of the sentence, and discards any
mesages or data that does not have valid NMEA format without any adverse effects to the
parser itself in case binary messages (essentially random noise) are present on this serial port.
2.5.2.1 Lock Status Definition
Lock Status definitions:
The third binary bit in the status parameter is encoded in the same status as the LOCK-OK LED.
2.5.2.2 Health Status Definition
The proprietary JLT NMEA-like status sentence contains a hexadecimal status word that shows
system health, and oscillator status. Encoding is done by each bit indicating a specific parameter, and
thus all bits are orthogonal to each other and can be easily decoded.
The definition of the health parameter is as follows:
Value State
0 TCXO warmup
1 Holdover
2 Locking (TCXO training)
4 [Value not defined]
5 Holdover, but still phase locked (stays in this state for about 100s after GPS lock
is lost)
6 Locked, no pending events, and GPS is active
If the TCXO coarse-DAC is maxed-out at 255 HEALTH STATUS |= 0x1
If the TCXO coarse-DAC is mined-out at 0 HEALTH STATUS |= 0x2
If the phase offset to UTC is >250ns HEALTH STATUS |= 0x4
If the run-time is < 300 seconds HEALTH STATUS |= 0x8
If the GPS is in holdover > 60s HEALTH STATUS |= 0x10
If the Frequency Estimate is out of bounds HEALTH STATUS |= 0x20