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<reference id="GUID-CCEAFF83-11E6-511D-9A3E-E5D986F4FCF8" xml:lang="en"><title> NMEA Messages</title><shortdesc>This document describes the NMEA messages supported by

the Bluetooth GPS PSY. </shortdesc><prolog><metadata><keywords/></metadata></prolog><refbody>

<section id="GUID-6B7BCA18-2C7B-405D-AAF5-6F2A9B6DE074"><p>The target audiences for this document are device creators

and GPS hardware vendors who want to know which NMEA messages are

sent from the PSY to a GPS device and which messages the PSY expects

to receive from the device. </p> </section>

<section id="GUID-5303CC1B-0A5D-4F0F-977E-7E9B31F48F20"><title>Introduction</title> <p>The Bluetooth GPS PSY communicates

with a GPS device using the NMEA 0183 protocol. </p> <p>The messages

used for communication between the PSY and a GPS device are listed

in the following sections. </p> <p>Note: The SiRF NMEA messages (those

beginning with <codeph>$PSRF</codeph>) are not sent when a GPS device

reports that it supports PNOK extensions. Positioning and power management

messages for PNOK compatible GPS devices are described in <xref href="GUID-B143DF73-98F6-5491-8328-F5E12AE493A0.dita">PNOK messages</xref>. </p> </section>

<section id="GUID-E16E33C1-6B45-4131-ABE7-ED6DCA0BFF7F"><title>Required background</title> <p>Familiarity with the

following is helpful in understanding this document: </p> <ul>

<li id="GUID-F41B3CC6-67D9-59D8-9027-1F0DE6067899"><p> <xref href="http://www.nmea.org/content/nmea_standards/nmea_standards.asp" scope="external">The NMEA 0183 Protocol</xref>  </p> </li>

<li id="GUID-C33FA805-D195-57EA-93C4-D9D1E82D5C70"><p> <xref href="http://www.sirf.com/" scope="external">SiRF Binary Protocol

Reference Manual</xref>  </p> </li>

<li id="GUID-786BCAA8-399D-5B9D-8D37-3314F1318CE5"><p> <xref href="http://www.sirf.com/" scope="external">SiRF NMEA Reference Manual</xref>  </p> </li>

</ul> </section>

<section id="GUID-A9400274-9901-40F6-ACE0-090E8C19A56C"><title>GPS initialisation messages</title> <p>The PSY sends

initialisation messages to the GPS device in order to: </p> <ul>

<li id="GUID-F842CA2B-7B7E-5980-BF6E-D542409A8771"><p>Set the device

to NMEA mode (to return messages defined by NMEA 0183). </p> </li>

<li id="GUID-54F71FA5-D896-58AA-B4D6-B9F8BE9485D7"><p>Initialise the

device's power mode. </p> </li>

<li id="GUID-87108C5F-7785-547F-99FB-24CDB26B71C7"><p>Specify which

NMEA messages to return, and their rate of return. </p> </li>

</ul> <p><b>Setting NMEA mode</b> </p> <p>The PSY sends an SiRF binary protocol

initialisation message to switch the GPS device to NMEA mode. The

message is "Switch To NMEA Protocol – Message ID 129" (<codeph>0x81</codeph> hexadecimal). This message switches a serial port from binary to

NMEA protocol and sets message output rates and bit rate on the port. </p> <p>The message is: <codeph>\xA0\xA2\x00\x18\x81\x02\x01\x01\x00\x01\x05\x01\x05\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x12\xC0\x01\x6A\xB0\xB3\r\n</codeph>. </p> <p><b>Requesting NMEA messages</b> </p> <p>The PSY sends SiRF NMEA messages

"103—Query/Rate Control" to specify which NMEA messages the device

must return and the rate at which to return them. </p> <p>The NMEA

messages <codeph>GPGGA</codeph>, <codeph>GPRMC</codeph>, <codeph>GPGSV</codeph> and <codeph>GPGSA</codeph> are required with an update interval

of one second. </p> <p>The PSY sends <codeph>$PSRF103</codeph> messages

to the GPS device as a concatenated message list. The following table

contains the details of the messages sent from the PSY to the GPS

device. </p> <table id="GUID-722D5AA5-4C24-59DD-A875-105D4798A20A">

<tgroup cols="3"><colspec colname="col0"/><colspec colname="col1"/>

<colspec colname="col2"/>

<thead>

<row>

<entry>Sent Messages</entry>

<entry>Meaning</entry>

<entry>Notes</entry>

</row>

</thead>

<tbody>

<row>

<entry><p> <codeph> $PSRF103,0,0,1,1*25\r\n</codeph>  </p> </entry>

<entry><p>Sets the device to return GGA messages with an interval

of 1 second. </p> </entry>

<entry><p>Message GGA returns time, position fix and fix type data. </p> </entry>

</row>

<row>

<entry><p> <codeph>$PSRF103,2,0,1,1*27\r\n</codeph>  </p> </entry>

<entry><p>Sets the device to return GSA messages with an interval

of 1 second. </p> </entry>

<entry><p>Message GSA returns GPS receiver operating mode, information

about the satellites used to obtain the position fix, and Dilution

of Position (DOP) data. </p> </entry>

</row>

<row>

<entry><p> <codeph>$PSRF103,3,0,1,1*26\r\n</codeph>  </p> </entry>

<entry><p>Sets the device to return GSV messages with an interval

of 1 second. </p> </entry>

<entry><p>Message GSV returns the number of GPS satellites in view,

satellite ID numbers, elevation, azimuth and Signal to Noise Ratio

(SNR) data. </p> </entry>

</row>

<row>

<entry><p> <codeph> $PSRF103,4,0,1,1*21\r\n</codeph>  </p> </entry>

<entry><p>Sets the device to return RMC messages with an interval

of 1 second. </p> </entry>

<entry><p>Message RMC returns time, date, position, course and speed

data. </p> </entry>

</row>

</tbody>

</tgroup>

</table> <p>The concatenated message list that is sent to the device

is: <codeph>$PSRF103,0,0,1,1*25\r\n$PSRF103,2,0,1,1*27\r\n\      

       $PSRF103,3,0,1,1*26\r\n$PSRF103,4,0,1,1*21\r\n</codeph>. </p> <p><b>Controlling device power mode</b> </p> <p>The PSY sends a full

power mode message (see below) when it initialises the GPS device. </p> </section>

<section id="GUID-AD39B01E-8806-4268-86A1-9AD05B3CBE91"><title>Full power mode message</title> <p>The PSY sends $PSRF107

messages with the parameters to switch the device to full power mode

when required. This message turns off device trickle power mode if

this is the current power state of the GPS device. </p> <p>The message

sent is: <codeph>$PSRF107,0,1000,1000*3d\r\n</codeph>. </p> </section>

</refbody></reference>