User`s guide

Chapter 3 - Receiver Descriptions

NMEA Command Examples

1. Assume the user desires a single (polled) RMC message. The required

command string (without the optional checksum) is:

$PMOTG,RMC,0000,<CR><LF>

2. Assuming that the user now desires the RMC message to be sent once each second, the

command string would change to:

$PMOTG,RMC,0001,<CR><LF>

NMEA Response Examples

The response to the command in Example 1 above would be:

$GPRMC,hhmmss.ss,a,ddmm.mmmm,n,ddmm.mmmm,w,z.z,y.y,d.d,v*CC<CR><LF>

where:

• ‘$GPRMC’ is the message header

• ‘hhmmss.ss’ is the UTC time of the position fix in hours, minutes, and seconds

• ‘a’ is the current position fix status with ‘A’ designating a valid position, and ‘V’ indicating

an invalid position

• ‘ddmm.mmmm’ is the current latitude in degrees and minutes

• ‘n’ is the direction of the latitude with ‘N’ indicating North and ‘S’ indicating South

• ‘dddmm.mmmm’ is the current longitude in degrees and minutes

• ‘w’ is the direction of the longitude with ‘W’ indicating West and ‘E’ indicating East

• ‘z.z is the current ground-speed in knots

• ‘y.y’ is the current direction, referenced to true North

• ‘ddmmyy’ is the UTC date of the position fix

• ‘d.d’ is the magnetic variation in degrees (always 0.0 with M12+)

• ‘v’ is the direction of the variation (always nulled with M12+)

• ‘CC’ is the checksum

As noted previously, NMEA messages can vary in length. If any value has not been determined

yet the data position will be nulled. For example, if you request the RMC message before the

receiver has tracked any satellites and developed a position solution, the response will look like

this:

$GPRMC,,V,,,,,,,,,,*CC<CR><LF>

For the case where more than one output message is scheduled during the same one second

interval, the receiver will output all scheduled messages but will attempt to limit the number of

bytes transmitted each second to 400 bytes. For the case of multiple output messages, if the next

message to be sent fits into the 400 byte length goal, then the message will be output. For

Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05