Novatel OM-20000041 用户手册

3

Data Logs

44

 MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 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:

$COM1,747,347204.80,$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 

 command in Chapter 2, Page 23 and Appendix C, Page 79.

Example 1b illustrates what would result if $

TM1B

 binary log data were input to the accepting port 

(i.e., log com2 com1a onchanged).

$COM1,747,349005.18,<AA>D<DC1>k<ETX><NUL><NUL><NUL>4<NUL><NUL><NUL>
<EB><STX><NUL><NUL><FE>3M<NAK>A<VT><83><D6>o<82><C3>Z<BE><FC><97>I
<91><C5>iV><7F><8F>O<NUL><NUL><NUL>"<C0><NUL><NUL><NUL><NUL>*6A

As can be seen, the $

TM1B

 binary data at the accepting port was converted to a variation of ASCII hexadecimal

before it was passed through to 

COM

2 port for logging (

MESSAGES

 command set to 

OFF

).

Format:

Message ID =

30 for COM1B; 31 for COM2B

Message byte count = 24 + (length of pass-through data string received (80 maximum))

1

Sync

3

char

0

(header)

Checksum

1

char

3

Message ID

4

integer

4

Message byte count

4

integer

8

2

Week number

4

integer

weeks

12

3

Seconds of week

8

double

seconds

16

4

Pass-through data as 
received

variable

char

24 + (variable data)