Linx Technologies RXM-GPS-FM - Manual (Page 12)

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The write and read messages are shown in Figure 20. A write message
triggers an acknowledgement from the module. A read message triggers a
response message containing the requested information.
The module responds to commands with response messages. The
acknowledge message is formatted as shown in Figure 21.
Input Messages
The following outlines the serial commands input into the module for
configuration. There are 3 types of input messages: commands, writes and
reads. The module outputs a response for each input message.
The commands are used to change the operating state of the module.
The writes are used to change the module’s configuration and the reads
are used to read out the current configuration. Messages are formatted as
shown in Figure 18. All fields in each message are separated by a comma.
Figure 19 shows the input commands.
Serial Data Structure
Name Example Description
Start Sequence $PMTK
Message ID
Message Identifier consisting of three numeric
characters.
Payload DATA Message specific data.
Checksum CKSUM
CKSUM is a two-hex character checksum as
defined in the NMEA specification, NMEA-0183
Standard for Interfacing Marine Electronic Devices.
Checksums are required on all input messages.
End Sequence
Each message must be terminated using Carriage
Return (CR) Line Feed (LF) (\r\n, 0x0D0A) to cause
the receiver to process the input message. They
are not printable ASCII characters, so are omitted
from the examples.
Figure 18: Serial Data Structure
Figure 20: Input Write and Read Messages
Input Write and Read Messages
Description Write ID Read ID Response ID
Position Fix Interval 300 400 500
DGPS Source 301 401 501
SBAS Enable 313 413 513
NMEA Output Messages 314 414 514
Set Datum 330 430 530
Static Navigation Threshold 386 447 527
Enable Ephemeris Prediction 869 869 869
Input Commands
Name Description
101 Hot Re-start
102 Warm Re-start
103 Cold Re-start
104 Restore Default Configuration
161 Standby Mode
220 Position Fix Interval
223 Ephemeris Data Receive Time
225 Receiver Duty Cycle
251 Baud Rate
Figure 19: Input Commands
Acknowledge Message
Name Example Description
Start Sequence $PMTK
Message ID 001 Acknowledge Identifier
Command CMD The command that triggered the acknowledge
Flag Flg
Flag indicating the outcome of the command
0 = Invalid Command
1 = Unsupported Command
2 = Valid command, but action failed
3 = Valid command and action succeeded
Checksum CKSUM
CKSUM is a two-hex character checksum as
defined in the NMEA specification, NMEA-0183
Standard for Interfacing Marine Electronic Devices.
Checksums are required on all input messages.
End Sequence
Each message must be terminated using Carriage
Return (CR) Line Feed (LF) (\r\n, 0x0D0A) to cause
the receiver to process the input message. They
are not printable ASCII characters, so are omitted
from the examples.
Figure 21: Acknowledge Message