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5 Special Pass-Through Logs
32 MiLLennium Command Descriptions Manual
5.2 ASCII LOG STRUCTURE
Example 1:
$COM1,747,347131.23,$TM1A,747,347131.000000000,0.000000058,0.00000
0024, -9.000000009,0*78<CR>*2E[CR][LF]
$COM1,747,347131.31,<LF>*4F[CR][LF]
$COM1,747,347131.40,Invalid Command Option<LF>*7C[CR][LF]
$COM1,747,347131.42,Com1>Invalid Command Option<LF>*30[CR][LF]
$COM1,747,347131.45,Com1>*0A[CR][LF]
Example 1, above, shows what would result if a GPSCard logged
TM1A data into the COM1 port of another
GPSCard, where the accepting card is redirecting this input data as a pass-through log to its
COM2 port (log com2
com1a onchanged). Under default conditions the two cards will "chatter" back and forth with the Invalid
Command Option message (due to the command interpreter in each card not recognizing the command prompts
of the other card). This chattering will in turn cause the accepting card to transmit new pass-through logs with the
response data from the other card. To avoid this chattering problem, use the GPSCard
MESSAGES command on the
accepting port to disable error reporting from the receiving port command interpreter or if the incoming data is of
no use to the GPSCard, then disable the command interpreter with the
ACCEPT NONE command.
If the accepting port's error reporting is disabled by
MESSAGES OFF, the $TM1A data record would pass through
creating two records as follows:
Example 1a:
$COM1,747,347204.80,$TM1A,747,347203.999999957,-
0.000000015,0.000000024,
-9.000000009,0*55<CR>*00[CR][LF]
$COM1,747,347204.88,<LF>*48[CR][LF]
The reason that two records are logged from the accepting card is because the first record was initiated by receipt
of the $
TM1A log's first terminator <CR>. Then the second record followed in response to the $TM1A log's second
terminator <LF>.
Note that the time interval between the first character received ($) and the terminating <LF> can be calculated by
differencing the two
GPS time tags (0.08 seconds). This pass-through feature is useful for time tagging the arrival
of external messages. These messages could be any user-related data. If the user is using this feature for tagging
external events then it is recommended that the command interpreter be disabled so that the GPSCard does not
respond to the messages. See the
ACCEPT command in Chapter 2 and Appendix C.
Example 1b illustrates what would result if $
TM1B binary log data were input to the accepting port
(i.e., log com2 com1a onchanged).
$port ID week seconds pass-through data *xx [CR][LF]
Field # Field type Data Description Example
1 $port ID Log header:
Identifies port accepting input data
$COM1
2 week GPS week number 747
3 seconds GPS seconds into the week at time of log 347131.23
4 pass-through data Data accepted into COM1
(up to 80 characters)
$TM1A,747,347131.000000000,
0.000000058,0.000000024,
-9.000000009,0*78<CR>
5 *xx Checksum *2E
6 [CR][LF] Sentence terminator [CR][LF]