1.5.1.4 Antenna Connector The GPS 15H & 15L sensors provide a MCX female connector for connection to an active GPS antenna, so the antennas cable should be terminated in MCX male. A suitable antenna is Garmins GA 27C Antenna (Garmin Part Number 010-10052-05). Other antennas that are terminated in male BNC connectors may be adapted via a Garmin MCX to BNC Adapter Cable (Garmin Part Number 010-10121-00).
Electrical Characteristics
1.5.2.1 Input Voltage GPS 15H: 8.0 VDC to 40 VDC unregulated GPS 15L: 3.3 VDC to 5.4 VDC (must have less than 100 mV peak-to-peak ripple)
1.5.2.2 Input Current GPS 15H: 60 mA peak, 50 mA nominal @ 8.0 VDC 40 mA peak, 33 mA nominal @ 12 VDC 15 mA peak, 12 mA nominal @ 40 VDC GPS 15L: 100 mA peak, 85 mA nominal @ 3.3 to 5.0 VDC
1.5.2.3 GPS Receiver Sensitivity -165 dBW minimum
Environmental Characteristics
Operating Temperature: Storage Temperature: -30C to +80C -40C to +90C
GPS 15H & 15L Technical Specifications Page 4

GPS Performance

1.5.4.1 Receiver WAAS Enabled, 12 parallel channel GPS receiver continuously tracks and uses up to 12 satellites (up to 11 with PPS active) to compute and update your position. 1.5.4.2 Acquisition Times Reacquisition: Less than 2 seconds Warm: Cold: AutoLocate: SkySearch: Approx. 15 seconds (all data known) Approx. 45 seconds (initial position, time, and almanac known; ephemeris unknown) 5 minutes (almanac known; initial position and time unknown) 5 minutes (no data known)
1.5.4.3 Update Rate 1 second default; NMEA 0183 output interval configurable from 1 to 900 seconds in 1-second increments. 1.5.4.4 Accuracy GPS Standard Positioning Service (SPS) Position: < 15 meters, 95% typical Velocity: 0.1 knot RMS steady state DGPS (USCG/RTCM) Position: 3-5 meters, 95% typical Velocity: 0.1 knot RMS steady state DGPS (WAAS) Position: < 3 meters, 95% typical Velocity: 0.1 knot RMS steady state PPS Time: 1 microsecond at rising edge of PPS pulse (subject to Selective Availability) Dynamics: 999 knots velocity (only limited at altitude greater than 60,000 feet), 6g dynamics

GPS 15H & 15L Technical Specifications Page 5

Interfaces

1.5.5.1 GPS 15H & 15L Electrical Characteristics True RS-232 output (Port 2 output not used at time of publication), asynchronous serial input compatible with RS-232 or TTL voltage levels, RS-232 polarity. User selectable NMEA 0183 baud rate (300, 600, 1200, 2400, 4800, 9600, 19200, 38400). Factory setting is 4800 baud.
1.5.5.2 Port 1 Protocols Configurable between NMEA 0183 Versions 2.00 and 3.00. ASCII output sentences: GPALM, GPGGA, GPGLL, GPGSA, GPGSV, GPRMC, and GPVTG (NMEA-approved sentences); and PGRMB, PGRME, PGRMF, PGRMM, PGRMT, and PGRMV (Garmin proprietary sentences). NMEA 0183 Outputs (see section 4.2 for full protocol specifications) Position, velocity and time Receiver and satellite status Differential Reference Station ID and RTCM Data age Geometry and error estimates NMEA 0183 Inputs (see section 4.1 for full protocol specifications) Initial position, date and time (not required) Earth datum and differential mode configuration command, PPS Enable, GPS satellite almanac Configurable for binary data output including GPS carrier phase data
1.5.5.3 Port 2 Protocols Real-time Differential Correction input (RTCM SC-104 message types 1, 2, 3, 7, and 9) 1.5.5.4 PPS 1 Hz pulse, programmable width, 1 s accuracy

Antenna Specifications

Should be an active antenna with the following specifications: Gain: Antenna should provide between 10 dB to 30 dB net gain between the antenna feed point and the connection to the GPS 15H & 15L. Consider all amplifier gains, filter losses, cable losses, etc. when calculating the gain. RF Connection: GPS 15H & 15L RF Connection: MCX Female connector (on the GPS 15H & 15L board). Antenna Connection: MCX Male connector (on the end of the antenna cable). Garmin Antenna: GPS 27C (Garmin Part Number 010-10052-05) provides the required MCX Male connector. Other Garmin antennas terminated in a BNC Male connector may also be used if a Garmin MCX to BNC Adapter Cable (Garmin Part Number 010-10121-00) is used. Place the MCX to BNC Adapter Cable between the connector on the end of the antenna cable and the connector on the GPS 15H & 15L.
GPS 15H & 15L Technical Specifications Page 6

Noise Figure/Gain:

The total noise figure on the external antenna must be 7 dB. Refer to the table below.

SNR (dB)

10.0 10.0

Gain (dB)

NF=1.3dB NF=2.3dB NF=3.3dB NF=4.3dB NF=5.3dB NF=6.3dB NF=7.3dB
Table 1: Gain vs. SNR for Given Noise Figure
Properly bias the antenna from an on-board source or an external source: Bias voltage from on-board source: GPS 15H supplies 3.3 VDC to the center conductor of the MCX female, relative to the connector shell ground. GPS 15L supplies 3.0 VDC to the center conductor of the MCX female, relative to the connector shell ground In both the GPS 15H and 15L, the source resistance of the DC supply to the center conductor of the connector is approximately 10 Ohms, which is included as a current limiting resistance. This resistance allows the receiver to survive momentary shorting of the antenna port. The GPS 15H and 15L sensors with serial numbers between 27700000 and 28099999 can detect if the antenna is shorted. GPS 15H and 15L sensors no in the serial number range listed above do not have a provision to protect against a continuously shorted antenna port. The antenna must not draw more than 60 mA. Bias voltage from external source: 4.0 to 8.0 VDC bias through the series combination of an on-board ~10 Ohm current limiting resistance and a Schottky diode. The antenna must not draw more than 60 mA.

GPS 15H & 15L Technical Specifications Page 7
GPS 15H & 15L WIRE DESCRIPTIONS AND WIRING DIAGRAMS
The GPS 15H-F & 15L-F use an eight-contact flex circuit LIF (low insertion force) connector. The GPS 15H-W & 15L-W use an eight-pin JST connector (mating wire harness included). See section 1.5.1.3.
GPS 15H & 15L WIRE DESCRIPTIONS
Signal Name BACKUP POWER Description This input provides external power to maintain the real-time clock. This enables the user to provide backup power if needed for longer than the on-board backup battery provides (roughly 21 days). Input voltage must be between +2.8 and +3.4 VDC. Power and Signal Ground GPS 15L: +3.3 to +5.4 VDC (100 mV ripple) input. Peak operating current is 100 mA. Nominal operating current is 85 mA. This voltage drives an LDO with a nominal 3.0 VDC output. GPS 15H: Unregulated 8.0 to 40 VDC input. Peak operating current is 40 mA @ 12 VDC input. Nominal operating current is 33 mA @ 12 VDC input. This voltage drives a switching regulator with a nominal 3.3 VDC output. Although a regulated supply is not required, the peak-to-peak voltage ripple on this line should be kept to less than 100 mV. Serial Asynchronous Output RS-232 compatible output normally provides serial data which is formatted per NMEA 0183, Version 2.0. This output is also capable of outputting phase data information; see Appendix B: Binary Phase Output Format for details. The NMEA 0183 baud rate is selectable in the range of 300 to 38400 baud. The default baud rate is 4800. First Serial Asynchronous Input RS-232 compatible with maximum input voltage range of -25 < V < 25. This input may also be directly connected to standard 3 to 5 VDC CMOS logic that utilizes RS-232 polarity. The low signal voltage requirement is < 0.6 V, and the high signal voltage requirement is > 2.4 V. Minimum load impedance is 500. This input may be used to receive serial initialization/ configuration data as specified in section 4.1 Received NMEA 0183 Sentences. This input allows the user to supply an external RF bias voltage in the range of 4 VDC to 8 VDC to the active antenna. The voltage should be from a clean, regulated supply and should be well isolated from potential sources of interference. The supply should not share RF current paths with other system devices such as microprocessors or other RF circuits. By default, the unit uses an internal voltage to power the active antenna. Note: This pin is only operational on units whose serial numbers are higher than the serial numbers given below: 010-00240-01 GPS 15H-W serial no. 81301857 010-00240-02 GPS 15L-W serial no. 81408976 010-00240-11 GPS 15H-F serial no. 81901632 010-00240-12 GPS 15L-F serial no. 82001471 One-Pulse-Per-Second Output Typical voltage rise and fall times are 100 ns. Impedance is 250. The open circuit output voltage toggles between the low (0 V) and the high (3.3 V for 15H and 3.0 V for 15L). The default format is a 100 ms wide active-high pulse at a 1 Hz rate, with the pulse width configurable in 20 ms increments. Rising edge is synchronized to the start of each GPS second. This output provides a nominal 450 mVp-p signal into a 50 load. The pulse time measured at the 50% voltage point will be approximately 15 ns earlier with a 50 load than with no load. Second Serial Asynchronous Input This input may be used to receive serial differential GPS data formatted per RTCM SC-104 Recommended Standards For Differential Navstar GPS Service, Version 2.2 (see section 4.5 for more details). Table 2: GPS 15H & 15L Wire Descriptions

RECEIVED NMEA 0183 SENTENCES
The following paragraphs define the sentences that can be received on the GPS sensors port. Null fields in the configuration sentence indicate no change in the particular configuration parameter. All sentences received by the GPS sensor must be terminated with <CR><LF>, the ASCII characters for carriage return (0D hexadecimal) and line feed (0A hexadecimal), respectively. The checksum *hh is used for parity checking data and is recommended for use in environments containing high electromagnetic noise. It is generally not required in normal PC environments. When used, the parity bytes (hh) are the ASCII representation of the upper and lower nibbles of the exclusive-or (XOR) sum of all the characters between the $ and * characters, non-inclusive. The hex representation must be a capital letter, such as 3D instead of 3d. Sentences may be truncated by <CR><LF> after any data field and valid fields up to that point will be acted on by the sensor.
Almanac Information (ALM)
The $GPALM sentence can be used to initialize the GPS sensors stored almanac information in the unlikely event of non-volatile memory loss, or after storage of greater than six months without tracking GPS satellites. $GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF> <1> <2> <3> <4> <5> <6> <7> <8> <9> <10> <11> <12> <13> <14> <15> Total number of ALM sentences to be transmitted by the GPS sensor during almanac download. This field can be null or any number when sending almanac to the GPS sensor. Number of current ALM sentence. This field can be null or any number when sending almanac to the GPS sensor. Satellite PRN number, 01 to 32 GPS week number SV health, bits 17-24 of each almanac page Eccentricity Almanac reference time Inclination angle Rate of right ascension Root of semi major axis Omega, argument of perigee Longitude of ascension node Mean anomaly af0 clock parameter af1 clock parameter

GPS 15H & 15L Technical Specifications Page 12
Additional Sensor Configuration Information (PGRMC1)
The $PGRMC1 sentence provides additional information used to configure the GPS sensor operation. Configuration parameters are stored in non-volatile memory and retained between power cycles. The GPS sensor echoes this sentence upon its receipt if no errors are detected. If an error is detected, the echoed PGRMC1 sentence will contain the current default values. Current default values can also be obtained by sending $PGRMC1E to the GPS sensor. $PGRMC1,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>*hh<CR><LF> <1> <2> <3> <4> <5> <6> <7> <8> <9> NMEA 0183 output time 1-900 (sec) Binary Phase Output Data, 1 = Off, 2 = On Automatic Position Averaging when Stopped, 1 = Off, 2 = On DGPS beacon frequency 0.0, 283.5 325.0 kHz in 0.5 kHz steps DGPS beacon bit rate 0, 25, 50, 100, or 200 bps DGPS beacon scanning, 1 = Off, 2 = On NMEA 0183 version 2.30 mode indicator, 1 = Off, 2 = On DGPS mode, A = Automatic, W = WAAS Only, R = RTCM Only, N = None (DGPS disabled) Power Save Mode, P = Power Save mode, N = Normal
At power up or external reset, a stored beacon frequency other than 0.0 causes the GPS sensor to tune the beacon receiver. Configuration changes take effect immediately, with the exception of Binary Phase Output Data, which takes effect on the next power cycle or a reset event. A reset can be commanded by sending the sentence $PGRMI,,,,,,,R (refer to section 4.1.2). If the GPS sensor is in the Binary data mode, it is necessary to send the following eight-byte data stream to the COM 1 input to temporarily change the data format to NMEA 0183. Then send a PGRMC1 sentence that turns off the Binary Phase Output Data format: 10 0A 00 CE (Hexadecimal)
Output Sentence Enable/Disable (PGRMO)
The $PGRMO sentence provides the ability to enable and disable specific output sentences. The following sentences are enabled at the factory: GPGGA, GPGSA, GPGSV, GPRMC, PGRMB, PGRME, PGRMM, PGRMT, and PSLIB. $PGRMO,<1>,<2>*hh<CR><LF> Target sentence description (e.g., PGRMT, GPGSV, etc.) Target sentence mode, where: 0 = disable specified sentence 1 = enable specified sentence 2 = disable all output sentences (except PSLIB) 3 = enable all output sentences (except GPALM) 4 = restore factory default output sentences The following notes apply to the PGRMO input sentence: 1. If the target sentence mode is 2 (disable all), 3 (enable all), or 4 (restore defaults), the target sentence description is not checked for validity. In this case, an empty field is allowed (e.g., $PGRMO,,3), or the mode field may contain from 1 to 5 characters. If the target sentence mode is 0 (disable) or 1 (enable), the target sentence description field must be an identifier for one of the sentences that can be output by the GPS sensor. If either the target sentence mode field or the target sentence description field is not valid, the PGRMO sentence will have no effect. $PGRMO,GPALM,1 causes the GPS sensor to transmit all stored almanac information. All other NMEA 0183 sentence transmission is suspended temporarily. $PGRMO,,G causes the COM 1 port to change to Garmin Data Transfer format for the duration of the power cycle. The Garmin mode is required for GPS 15H & 15L product software updates. <1> <2>

2. 3. 4. 5.

GPS 15H & 15L Technical Specifications Page 13
Tune DGPS Beacon Receiver (PSLIB)
The $PSLIB sentence provides the ability to tune a Garmin GBR 21, GBR 23 or equivalent beacon receiver. $PSLIB,<1>,<2>*hh<CR><LF> <1> Beacon tune frequency, 0.0, 283.5325.0 kHz in 0.5 kHz steps <2> Beacon bit rate, 0, 25, 50, 100, or 200 bps If valid data is received, the GPS sensor stores it in the EEPROM and echoes the PSLIB command to the beacon receiver. If the GPS sensor is using any stored beacon frequency other than 0.0, it will tune the beacon receiver once immediately after power up or external reset.
GPS 15H & 15L Technical Specifications Page 14
TRANSMITTED NMEA 0183 SENTENCES
The subsequent paragraphs define the sentences that can be transmitted on COM 1 by the GPS sensor.
Sentence Transmission Rate
Sentences are transmitted with respect to the user-selected baud rate. Regardless of the selected baud rate, the information transmitted by the GPS sensor is referenced to the one-pulse-per-second output pulse immediately preceding the GPRMC sentence, or whichever sentence is output first in the burst (see Table 3 below). The GPS sensor transmits each sentence (except where noted in particular transmitted sentence descriptions) at a periodic rate based on the user-selected baud rate and user-selected output sentences. The GPS sensor transmits the selected sentences contiguously. The contiguous transmission starts at a GPS second boundary. Determine the length of the transmission with the following equation and Tables 3 and 4: length of transmission = total characters to be transmitted --------------------------------------------characters transmitted per second
Sentence Output by Default? Maximum Characters GPRMC 74 GPGGA 82 GPGSA 66 GPGSV 70 PGRME 35 GPGLL 44 GPVTG 42 PGRMV 32 PGRMF 82 PGRMB 40 PGRMM 32 PGRMT Once per minute 50 Table 3: NMEA 0183 Output Sentence Order and Size Baud Characters per Second Table 4: Characters per Second for Available Baud Rates The maximum number of fields allowed in a single sentence is 82 characters including delimiters. Values in the table include the sentence start delimiter character $ and the termination delimiter <CR><LF>. The factory set defaults result in a once per second transmission at the NMEA 0183 specification transmission rate of 4800 baud.

GPS 15H & 15L Technical Specifications Page 15

Transmitted Time

The GPS sensor outputs UTC (Coordinated Universal Time) date and time of day in the transmitted sentences. Before the initial position fix, the on-board clock provides the date and time of day. After the initial position fix, the date and time of day are calculated using GPS satellite information and are synchronized with the one-pulse-per-second output. The GPS sensor uses information obtained from the GPS satellites to add or delete UTC leap seconds and correct the transmitted date and time of day. The transmitted date and time of day for leap second correction follow the guidelines in National Institute of Standards and Technology Special Publication 432 (Revised 1990). This document is for sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C., 20402, U.S.A. When a positive leap second is required, one second is inserted at the beginning of the first hour (0h 0m 0s) of the day that the positive leap is occurring. The minute containing the leap second is 61 seconds long. The GPS sensor would have transmitted this information for the leap second added December 31, 1998 as follows: $GPRMC,235959,A,3851.3651,N,09447.9382,W,000.0,221.9,071103,003.3,E*69 $GPRMC,000000,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*67 $GPRMC,000000,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*67 $GPRMC,000001,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*66 If a negative leap second should be required, one second is deleted at the end of some UTC month. The minute containing the leap second will be only 59 seconds long. In this case, the GPS sensor will not transmit the time of day 0h 0m 0s (the zero second) for the day from which the leap second is removed. $GPRMC,235959,A,3851.3650,N,09447.9373,W,000.0,000.0,111103,003.3,E*69 $GPRMC,000001,A,3851.3650,N,09447.9373,W,000.0,000.0,121103,003.3,E*6A $GPRMC,000002,A,3851.3650,N,09447.9373,W,000.0,000.0,121103,003.3,E*69
Global Positioning System Almanac Data (ALM)
Almanac sentences are not normally transmitted. Almanac transmission can be initiated by sending the GPS sensor a $PGRMO,GPALM,1 command. Upon receipt of this command, the GPS sensor transmits available almanac information on GPALM sentences. During the transmission of almanac sentences, other NMEA 0183 data output is suspended temporarily. $GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF> <field information> can be found in section 4.1.1.

4.2.15 DGPS Beacon Information (PGRMB)
$PGRMB,<1>,<2>,<3>,<4>,<5>,K,<6>,<7>*hh<CR><LF> <1> <2> <3> <4> <5> <6> <7> <8> Beacon tune frequency, 0.0, 283.5325.0 kHz in 0.5 kHz steps Beacon bit rate, 0, 25, 50, 100, or 200 bps Beacon SNR, 0 to 31 Beacon data quality, 0 to 100 Distance to beacon reference station in kilometers Beacon receiver communication status (0 = Check Wiring, 1 = No Signal, 2 = Tuning, 3 = Receiving, 4= Scanning) DGPS fix source (R = RTCM, W = WAAS, N = Non-DGPS Fix) DGPS mode, A = Automatic, W = WAAS Only, R = RTCM Only, N = None (DGPS disabled)
GPS 15H & 15L Technical Specifications Page 19

BAUD RATE SELECTION

Baud rate selection can be performed by sending the appropriate configuration sentence to the GPS sensor as described in the $PGRMC section 4.1.3, field <10>.
ONE-PULSE-PER-SECOND (PPS) OUTPUT
The highly accurate one-pulse-per-second (PPS) output is provided for applications requiring precise timing measurements. The signal is generated after the initial position fix has been calculated and continues until power down. The rising edge of the signal is synchronized to the start of each GPS second. Regardless of the selected baud rate, the information transmitted by the GPS 15H & 15L is referenced to the pulse immediately preceding the NMEA 0183 RMC sentence. The accuracy of the one-pulse-per-second output is maintained only while the GPS 15H & 15L can compute a valid position fix. To obtain the most accurate results, the one-pulse-per-second output should be calibrated against a local time reference to compensate for cable and internal receiver delays and the local time bias. The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 ms and 980 ms as described in $PGRMC section 4.1.3, field <13>.

RECEIVED RTCM DATA

Position accuracy of less than 5 meters can be achieved with the GPS 15H & 15L by using Differential GPS (DGPS) real-time pseudo-range correction data in RTCM SC-104 format, with message types 1, 2, 3, 7, and 9. These corrections can be received by the GPS 15H & 15L on COM 2. The RTCM data must be received at the same baud rate as the COM 1 port. For details on the SC-104 format, refer to RTCM Paper 134-89/SC 104-68 by the Radio Technical Commission for Maritime Services.

PICO DE LAS NIEVES - Canary Islands PITCAIRN ASTRO 1967 - Pitcairn Island PUERTO RICO - Puerto Rico, Virgin Islands QATAR NATIONAL - Qatar QORNOQ - South Greenland REUNION - Mascarene Island ROME 1940 - Sardinia Island RT 90 - Sweden PROVISIONAL SOUTH AMERICAN 1956 - Bolivia, Chile, Colombia, Ecuador, Guyana, Peru, Venezuela SOUTH AMERICAN 1969 - Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay, Peru, Venezuela, Trinidad and Tobago SOUTH ASIA - Singapore PROVISIONAL SOUTH CHILEAN 1963 - South Chile SANTO (DOS) - Espirito Santo Island SAO BRAZ - Sao Miguel, Santa Maria Islands (Azores) SAPPER HILL 1943 - East Falkland Island SCHWARZECK - Namibia SOUTHEAST BASE - Porto Santo and Madeira Islands SOUTHWEST BASE - Faial, Graciosa, Pico, Sao Jorge, and Terceira Islands (Azores) TIMBALAI 1948 - Brunei and East Malaysia (Sarawak and Sabah) TOKYO - Japan, Korea, Okinawa TRISTAN ASTRO 1968 - Tristan da Cunha User defined earth datum VITI LEVU 1916 - Viti Levu Island (Fiji Islands) WAKE-ENIWETOK 1960 - Marshall Islands WORLD GEODETIC SYSTEM 1972 WORLD GEODETIC SYSTEM 1984 ZANDERIJ - Surinam CH-1903 - Switzerland Hu - Tzu - Shan Indonesia 74 Austria Potsdam Taiwan - modified Hu-Tzu-Shan GDA - Geocentric Datum of Australia Dutch
GPS 15H & 15L Technical Specifications Page 23
APPENDIX B: BINARY PHASE OUTPUT FORMAT
In binary phase output mode, GPS 15H & 15L series products transmit two types of packets once per second. One record contains primarily post-process information such as position and velocity information. The second record contains receiver measurement information. For the GPS 15H & 15L, the records are sent at a default baud rate of 9600 baud, 8 data bits, and no parity. To turn these records on, use the $PGRMC1 NMEA sentence as described in section 4 GPS 15H & 15L Software Interface. (Refer to the Garmin GPS Interface Specification for details on how to form and parse Garmin packets. At the time of this printing, these specs are available from the technical support section of our Web site: http://www.garmin.com/support/commProtocol.html.) Note: The satellite data information is also enabled when the position record is enabled. Records sent over RS232 begin with a delimiter byte (10 hex). The second byte identifies the record type (33 hex for a position record and 34 hex for a receiver measurement). The third byte indicates the size of the data. The fourth byte is the first byte of data. The data is then followed by a checksum byte, a delimiter byte (10 hex), and an end-of-transmission character (03 hex). Additionally, any DLEs (0x10) that appear between the delimeters are escaped with a second DLE. Refer to the end of this section for sample code that strips off the DLEs and ETXs. RS232 Packet: - 0x10 - 0x## - 0x## - data bytes - 0x## - 0x10 - 0x03 (DLE is first byte) (Record ID single byte) (Number of data bytes single byte) (See descriptions below) (2s complement of the arithmetic sum of the bytes between the delimiters) (DLE) (ETX is last byte)

The data bytes of each packet contain the record specified by the record ID. A description of each record follows.

Satellite Data Record

The satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain the data for the 12 channels as described below. For each satellite, the following data is available: typedef struct { uint8 uint16 uint8 uint16 uint8 svid; snr; elev; azmth; status; //space vehicle identification (132 and 3364 for WAAS) //signal-to-noise ratio //satellite elevation in degrees //satellite azimuth in degrees //status bit-field

} cpo_sat_data;

GPS 15H & 15L Technical Specifications Page 24
The status bit field represents a set of booleans described below: Bit Meaning when bit is one (1) 0 The unit has ephemeris data for the specified satellite. 1 The unit has a differential correction for the specified satellite. 2 The unit is using this satellite in the solution. This pattern is repeated for all 12 channels for a total of 12 X 7 bytes = 84 (0x54) bytes : typedef struct { cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data cpo_sat_data } cpo_all_sat_data The RS-232 Packet for the Satellite Record looks like: - 0x10 - 0x72 - 0x54 - cpo_all_sat_data - 0x## - 0x10 - 0x03 (2s complement of the arithmetic sum of the bytes between the delimiters) (DLE) (ETX is last byte) (DLE is first byte) (Record ID single byte) (Number of data bytes single byte)
GPS 15H & 15L Technical Specifications Page 25

Position Record

The Position Record has a record identifier of typedef struct { float alt; float epe; float eph; float epv; int fix; double gps_tow; double lat; double lon; float lon_vel; float lat_vel; float alt_vel; float msl_hght; int leap_sec; long grmn_days; } cpo_pvt_data; alt epe eph epv fix gps_tow lat lon lon_vel lat_vel alt_vel msl_hght leap_sec grmn_days Ellipsoid altitude (meters) Est pos error (meters) Pos err, horizontal (meters) Pos err, vertical (meters) 0 = no fix; 1 = no fix; 2 = 2D; 3 = 3D; 4 = 2D differential; 5 = 3D differential; 6 and greater - not defined GPS time of week (sec) Latitude (radians) Longitude (radians) Longitude velocity (meters/second) Latitude velocity (meters/second) Altitude velocity (meters/second) Mean sea level height (meters) UTC leap seconds Garmin days (days since December 31, 1989)
Receiver Measurement Record
typedef struct { unsigned long double unsigned int char unsigned char char char } cpo_rcv_sv_data; typedef struct { double int cpo_rcv_sv_data } cpo_rcv_data; rcvr_tow rcvr_wn cycles pr phase slp_dtct snr_dbhz 190-00266-01 cycles; pr; phase; slp_dtct; snr_dbhz; svid; valid;

GPS 15H & 15L Technical Specifications Page 28
APPENDIX D: EPHEMERIS DATA DOWNLOAD (PROGRAMMING EXAMPLE)

Synopsis

This section describes, using an example, how to download ephemeris information from a Garmin 15, 16, 17 or 18 family GPS unit with the exception of the GPS 15-W and the GPS 15-F.
Garmin Binary Format Review
In order to download the ephemeris data, you must first command the unit to output information in Garmin Binary Format (Garmin mode) instead of the default NMEA output format. To put the unit in Garmin mode, connect to the unit using a terminal program and send the following NMEA sentence: $PGRMO,,G*hh<CR><LF> The checksum *hh is used for parity checking data and is not required, but is recommended for use in environments containing high electromagnetic noise. It is generally not required in normal PC environments. When used, the parity bytes (hh) are the ASCII representation of the exclusive-or (XOR) sum of all the characters between the "$ and * characters, non-inclusive. Sentences may be truncated by <CR><LF> after any data field and valid fields up to that point are acted on by the GPS sensor. The unit stays in Garmin mode until the next power cycle. Now that unit is in Garmin binary format, transmitted and received packets are structured as follows: Byte Description Packet Delimiter Packet ID (type) Data Size Data bytes. Checksum Name DLE ID SIZE DATA Notes 0x10 Packet type Number of bytes in data portion(not including escaped DLEs. See below) Not to exceed 256 bytes. 2s complement of the arithmetic sum of all the bytes from the Packet ID byte to the last DATA byte(inclusive) not counting escaped DLEs. See below DLE 0x10 ETX 0x03

CHKSUM

Packet Delimiter End of Packet
The DLE (0x10) is a delimiter byte used in conjunction with the ETX byte to determine beginning and ending of a packet. However, a 0x10 could appear in the data itself, so if this occurs the byte is escaped with another DLE byte (sometimes referred to as DLE stuffing). In other words, if a DLE occurs in the data, another DLE is transmitted immediately after to indicate that it is a data byte and it is not being used as a delimiter. Note that the size byte of the packet does not count the second DLE byte in an escaped DLE pair in the data field. Since a DLE that is a part of the data will have a second DLE to escape it, a single DLE followed by an ETX byte means that the end of a packet has been reached. In order to interpret these packets properly, one must remove the escaped DLE bytes. This can be achieved using an algorithm similar to the Sample C Code fragment on the previous page.
GPS 15H & 15L Technical Specifications Page 29
Ephemeris Download Procedure
The following is the sequence of events that occurs when downloading ephemeris data. Send a packet containing the command that requests ephemeris data (IOP_DOWN_LOAD_EPH). The packet should look like this: TX Packet: Ephemeris Data Request Byte Description Name HEX Value Delimiter DLE 0x10 Command Data ID IOP_CMND_DATA 0x0A Number of bytes in data SIZE 0x02 Request to D/L ephemeris IOP_DOWN_LOAD_EPH 0x5D Pad to 2 bytes DATA 0x00 Checksum calculation CHKSUM 0x97* Delimiter DLE 0x10 End ETX 0x03 * From now on, checksum calculation will not be shown for every packet example The unit returns an acknowledgement packet that looks like this: RX Packet: Acknowledgement Byte Description Delimiter Acknowledgement ID Number of bytes in data Request to D/L ephemeris Pad Checksum calculation Delimiter End of packet Name DLE IOP_ACK_BYTE SIZE IOP_CMND_DATA DATA CHKSUM DLE ETX HEX Value 0x10 0x06 0x02 0x0A 0x00 ---0x10 0x03

Then, the unit immediately sends a packet communicating how many data packets to expect for the ephemeris download (a maximum of twelve): RX Packet: Number of Data Packets to Expect Byte Description Delimiter Record ID Number of bytes in data Number of records Pad Checksum calculation Delimiter End of packet Name DLE IOP_RECORDS SIZE NUM_SV DATA CHKSUM DLE ETX HEX Value 0x10 0x1B 0x02 0x0C 0x00 ---0x10 0x03
This packet requires acknowledgement, as shown below (note that the data field contains the IOP_RECORDS ID to indicate the acknowledgement of the IOP_RECORDS packet): TX Packet: Acknowledgement Byte Description Delimiter Record ID Number of bytes in data Pad ID of packet being ACKd Checksum calculation Delimiter End of packet Name DLE IOP_ACK_BYTE SIZE DATA IOP_RECORDS CHKSUM DLE ETX HEX Value 0x10 0x06 0x02 0x00 0x1B ---0x10 0x03
GPS 15H & 15L Technical Specifications Page 30
Next, the unit sends the specified number of packets containing the ephemeris information. An example packet is shown below. Each packet should be acknowledged as before (be sure to modify the ACK packet to indicate what type of packet being acknowledgedfor ephemeris data the ID is 0x35). RX Packet: Ephemeris Data Byte Description Delimiter Ephemeris data ID Number of bytes in data Ephemeris data. Checksum calculation Delimiter End of packet Name DLE IOP_SPC_EPH_DATA SIZE DATA. CHKSUM DLE ETX HEX Value 0x10 0x35 0x78 ---. ---0x10 0x03
The data portion of each packet can then be parsed into an instance of the following structure. Each of these structures represents data from a single satellite.
typedef struct { sint16 wn; float toc; float toe; float af0; float af1; float af2; float ura; double e; double sqrta; double dn; double m0; double w; double omg0; double i0; float odot; float idot; float cus; float cuc; float cis; float cic; float crs; float crc; unsigned char iod; } SDM_spc_eph_type; /* ephemeris data record for SPC /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* /* week number (weeks) reference time of clock parameters (s) reference time of ephemeris parameters (s) clock correction coefficient - group delay (s) clock correction coefficient (s/s) clock correction coefficient (s/s/s) user range accuracy (m) eccentricity (-) square root of semi-major axis (a) (m**1/2) mean motion correction (r/s) mean anomaly at reference time (r) argument of perigee (r) right ascension (r) inclination angle at reference time (r) rate of right ascension (r/s) rate of inclination angle (r/s) argument of latitude correction, sine (r) argument of latitude correction, cosine (r) inclination correction, sine (r) inclination correction, cosine (r) radius correction, sine (m) radius correction, cosine (m) issue of data */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */ */

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Each data member of the ephemeris data structure is indexed into the data array of the ephemeris packet and cast as the appropriate data type. The indices are as follows (note that they correlate to the data members of the structure respectively):
#define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define IDX_EPH_WN IDX_EPH_TOC IDX_EPH_TOE IDX_EPH_AF0 IDX_EPH_AF1 IDX_EPH_AF2 IDX_EPH_URA IDX_EPH_E IDX_EPH_SQRTA IDX_EPH_DN IDX_EPH_M0 IDX_EPH_W IDX_EPH_OMG0 IDX_EPH_I0 IDX_EPH_ODOT IDX_EPH_IDOT IDX_EPH_CUS IDX_EPH_CUC IDX_EPH_CIS IDX_EPH_CIC IDX_EPH_CRS IDX_EPH_CRC IDX_EPH_IOD 116
The last packet is a download complete packet that looks like this: TX Packet: Download Complete Byte Description Delimiter Download Complete ID Number of bytes in data Ephemeris Download ID Pad Checksum calculation Delimiter End of packet Name DLE IOP_DL_CMPLT SIZE IOP_DOWN_LOAD_EPH DATA CHKSUM DLE ETX HEX Value 0x10 0x0c 0x02 0x5D 0x00 ---0x10 0x03
After properly acknowledging this packet (ACK the IOP_DL_CMPLT ID), the ephemeris download is complete.
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APPENDIX E: DECLARATION OF CONFORMITY
Hereby, Garmin Ltd., declares that this GPS 15H/15L is in compliance with the essential requirements and other relevant provisions of Directive 1999/5/EC.
For the latest free software updates (excluding map data) throughout the life of your Garmin products, visit the Garmin Web site at www.garmin.com.
Copyright 20042006 Garmin Ltd. or its subsidiaries Garmin International, Inc. 1200 East 151st Street, Olathe, Kansas 66062, U.S.A. Garmin (Europe) Ltd. Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9DL, U.K. Garmin Corporation No. 68, Jangshu 2nd Road, Shijr, Taipei County, Taiwan www.garmin.com Part Number 190-00266-01 Rev. D