49
Commands
Receiver commands allow you to change or query the status of various operating
parameters such as elevation mask, antenna altitude, position mode, etc. In this
context, set commands are used to change the G12’s operating parameters. Query
commands prompt the G12 to output status messages for parameter settings and
receiver operation. If an invalid set or query command is issued, a “not
acknowledged” (NAK) response is output:
$PASHR,NAK*30
Set command messages can be accepted by either serial port. When the G12
receives a valid set command message, it returns an "acknowledged" (ACK)
message:
$PASHR,ACK*3D
The G12 returns a NAK message if the command is invalid. The set command
$PASHS,SAV,Y<Enter> instructs the G12 to save user-entered operation
parameters; the G12 returns $PASHR,ACK*3D to acknowledge that the command
was valid and the instruction was carried out. The set command
$PASHS,SAV<Enter> is incomplete, and would cause the G12 to flag it as an
invalid command by responding with a “not acknowledged” response:
$PASHR,NAK*30.
The set command message structure is as follows:
“Header,Command ID,<Command Parameters>*Checksum<Enter>”
The header field always contains $PASHS. The command identifier field contains
a three character string and is followed by the command parameters. The checksum
is strictly optional. All set commands are terminated with an <Enter> or <CR><LF>
keystroke. All command string elements between the dollar sign ($) and the asterisk
(*), including the command parameters, are comma delimited; that is, the header,
the ID string, and the individual command parameters are separated by commas.
Enter the following set command to set the HDOP mask value:
$PASHS,HDP,6<Enter>
Query commands are used to request current GPS information and receiver status
information such as baud rate settings, position information, and tracking
information. Query command messages can be sent to either of the G12’s serial
ports. Most query commands allow you to designate the port from which the
response message is sent. The G12 acknowledges a valid query command
message by sending the requested response message through the specified port.
If the port is not specified in the query command, the response is sent from the
same port which received the query. The requested information is sent once each
time the command is issued and is not repeated.
G12RevD.book Page 49 Tuesday, April 2, 2002 4:33 PM
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