Global Sat ET-318 User manual

ET-318
Specifications are subject to be changed without notice.
Page 1 of 16
Version 1.3.1
GPS Engine Board
ET-318
Globalsat Technology Corporation
16F., No. 186, Jian-Yi Road, Chung-Ho City, Taipei Hsien 235, Taiwan
Tel: [phone]/ Fax: [phone]
[e-mail]
www.globalsat.com.tw
USGlobalSat, Inc.
14740 Yorba Court, Chino, CA 91710
Tel: [phone] / Fax: [phone]
[e-mail]
www.usglobalsat.com

ET-318
Specifications are subject to be changed without notice.
Page 2 of 16
Version 1.3.1
Product Information
Product Part I.D. ET-318
Product Description: SMT GPS Board
Product Features:
9SiRF StarIII/FLP chipset
9Very high sensitivity (Tracking Sensitivity: -159 dBm)
920 channels
9Extremely fast TTFF (Time To First Fix) at low signal levels
9Compact size
9One size component, easy to mount on another PCB board
9Support NMEA 0183 and SiRF binary protocol
Product Specifications
GPS Receiver
Chipset SiRF StarIII/FLP
Frequency L1, 1575.42 MHz
Code 1.023 MHz chip rate
Protocol NMEA 0183
Default: GGA, GSA, GSV, RMC, VTG, GLL
SiRF binary and NMEA Command
Available Baud Rate 4,800 to 57,600 bps adjustable
Channels 20
Sensitivity -159dBm
Cold Start 42 seconds average
Warm Start 38 seconds average
Hot Start 1 second average
Reacquisition 0.1 second average
Accuracy Position: 10 meters, 2D RMS
5 meters, 2D RMS, WAAS enabled

ET-318
Specifications are subject to be changed without notice.
Page 3 of 16
Version 1.3.1
Velocity: 0.1 m/s
Time: 1us synchronized to GPS time
Maximum Altitude 18,000 meter
Maximum Velocity 515 meter/second
Maximum Acceleration 4G
Jerk 20m/sec **3
Datum WGS-84 Default
Interface
I/O Connector Type
External Antenna Port
Physical Characteristic
Dimensions 0.6” x 0.55” x 0.11” (15.2 x 14 x 2.8 mm)
DC Characteristics
Power Supply 3.3V ±5% DC Input
Power Consumption 42mA (Continuous Mode)
25mA (Trickle Mode)
Environmental Range
Humidity Range 5% to 95% non-condensing
Operation Temperature -40C to 85C
Storage Temperature -40C to 85C
Recommended GPS Active/Passive Antenna Specifications
Frequency: 1575.42+2 MHz
Axial Ratio: 3 dB Typical
Output Impedance: 50Ω
Polarization: RHCP
Output VSWR: 1.5 Max.
Active Option: Low Noise Amplifier
Amplifier Gain: 20~26dB Typical
Output VSWR: 2.0 Max.
Noise Figure: 2.0 dB Max.

ET-318
Specifications are subject to be changed without notice.
Page 4 of 16
Version 1.3.1
2. Technical Information
Pin Assignment
Pin Signal Name I/O Description
1 GND G Analog Ground
2 RF_IN RF GPS Signal input
3 GND G Analog Ground
4 NRESET I Reset (Active low)
5 VCC_IN PWR DC Supply Voltage input
6 VBAT PWR Backup voltage supply
7 RXB I Serial port B
8 TXB O Serial port B
9 GND G Analog Ground
10 BOOTSEL Boot mode
11 TXA O Serial port A
12 RXA I Serial port A
13 GPIO1 I General –purpose I/O
14 GPIO14 I General –purpose I/O
15 TIMEMARK O One pulse per second
16 GPIO13 I General –purpose I/O
17 GPIO15 I General –purpose I/O
ET-318-01 Bottom View

ET-318
Specifications are subject to be changed without notice.
Page 5 of 16
Version 1.3.1
Pin Explanation
VCC_IN
This is the main DC supply for a 3.3V +- 5% DC input power module board.
GND
GND provides the ground for digital part.
BOOTSEL
Set this pin to high for programming flash.
RXA
This is the main receiver channel and is used to receive software commands to the board from SIRFdemo
software or from user written software. Pull up if not used.
RXB
This is the auxiliary receiving channel and is used to input differential corrections to the board to enable
DGPS navigation. Pull up if not used.
TXA
This is the main transmitting channel and is used to output navigation and measurement data to
SiRFdemo or user written software.
TXB
For user’s application (not currently used).
RF_IN
This pin receiver signal of GPS analog .due to the RF characteristics of the signal the design has to certain
criteria. The line on the PCB from the antenna (or antenna connector) has to be a controlled microstrip line
at 50Ω.
PPS
This pin provides one pulse-per-second output from the board, which is synchronized to GPS time. This is
not available in Trickle Power mode.
VBAT (memory Back-up)
This is the battery backup input that powers the SRAM and RTC when main power is removed. Typical
current draw is 15uA. Without an external backup battery, the module/engine board will execute a cold star
after every turn on. To achieve the faster start-up offered by a hot or warm start, a battery backup must be
connected. The battery voltage should be between 2.0v and 5.0v. (NOTE:This pin must be kept “HIGH” for
operation. From Vcc connect a 470 Ohm resistor in series with a 3.2v Zener diode to Ground. Then, connect the VBAT input to
Zener’s cathode to pull the input “HIGH”.)
TIMEMARK
This pin provides one pulse-per-second output from the board, which is synchronized to GPS time. This is
not available in Trickle Power mode.

ET-318
Specifications are subject to be changed without notice.
Page 6 of 16
Version 1.3.1
GPIO Functions
Several I/Os are connected to the digital interface connector for custom applications.
Application Circuit
R46
560R
1 2
C1
1U
1 2
TXA
RXB
RESET
BATTER Y
GPIO15
50 ohm microstrip line
GPIO13
RXA
R5
SAW FILTER
1 2
U1 GPS
6
5
4
3
2
1
7
8
9
10
11
12
13
14
15
17
16
VBAT
VCC_IN
NRESET
GND
RF_IN
GND
RXB
TXB
GND
BOOTSEL
TXA
RXA
GPIO1
GPIO14
TIMEMARK
GPIO15
GPIO13
GPIO1
3.3V
GPIO14
Antenna
1.
RB715F
3
1
2
BOOTSEL
TXB
C2
0.1U
1 2
option
VCC_RF
TIMEMARK
LNA
21 ..
Recommended Layout PAD

ET-318
Specifications are subject to be changed without notice.
Page 7 of 16
Version 1.3.1
Mechanical Layout

ET-318
Specifications are subject to be changed without notice.
Page 8 of 16
Version 1.3.1
3. Software Commands
NMEA Output Command
GGA-Global Positioning System Fixed Data
Table B-2 contains the values for the following example:
$GPGGA,161229.487,3723.2475,N,12158.3416,W,1,07,1.0,9.0,M,,,,0000*18
Table B-2 GGA Data Format
Name Example Units Description
Message ID $GPGGA GGA protocol header
UTC Time 161229.487 hhmmss.sss
Latitude 3723.2475 ddmm.mmmm
N/S Indicator N N=north or S=south
Longitude 12158.3416 dddmm.mmmm
E/W Indicator W E=east or W=west
Position Fix Indicator 1 See Table B-3
Satellites Used 07 Range 0 to 12
HDOP 1.0 Horizontal Dilution of Precision
MSL Altitude19.0 meters
Units M meters
Geoid Separation1meters
Units M meters
Age of Diff. Corr. second Null fields when DGPS is not used
Diff. Ref. Station ID 0000
Checksum *18
<CR><LF> End of message termination
SiRF Technology Inc. does not support geoid corrections. Values are WGS84 ellipsoid heights.
Table B-3 Position Fix Indicator
Value Description
0 Fix not available or invalid
1 GPS SPS Mode, fix valid
2 Differential GPS, SPS Mode , fix valid
3 GPS PPS Mode, fix valid

ET-318
Specifications are subject to be changed without notice.
Page 9 of 16
Version 1.3.1
GLL-Geographic Position-Latitude/Longitude
Table B-4 contains the values for the following example:
$GPGLL,3723.2475,N,12158.3416,W,161229.487,A*2C
Table B-4 GLL Data Format
Name Example Units Description
Message ID $GPGLL GLL protocol header
Latitude 3723.2475 ddmm.mmmm
N/S Indicator n N=north or S=south
Longitude 12158.3416 dddmm.mmmm
E/W Indicator W E=east or W=west
UTC Position 161229.487 hhmmss.sss
Status A A=data valid or V=data not valid
Checksum *2C
<CR><LF> End of message termination
GSA-GNSS DOP and Active Satellites
Table B-5 contains the values for the following example:
$GPGSA,A,3,07,02,26,27,09,04,15,,,,,,1.8,1.0,1.5*33
TableB-5GSADataFormat
Name Example Units Description
Message ID $GPGSA GSA protocol header
Mode1 A See Table B-6
Mode2 3 See Table B-7
Satellite Used107 Sv on Channel 1
Satellite Used102 Sv on Channel 2
.
Satellite Used1Sv on Channel 12
PDOP 1.8 Position dilution of Precision
HDOP 1.0 Horizontal dilution of Precision
VDOP 1.5 Vertical dilution of Precision
Checksum *33
<CR><LF> End of message termination
1. Satellite used in solution.

ET-318
Specifications are subject to be changed without notice.
Page 10 of 16
Version 1.3.1
TableB-6Mode1
Value Description
M Manual-forced to operate in 2D or 3D mode
A 2D automatic-allowed to automatically switch 2D/3D
TableB-7Mode2
Value Description
1 Fix Not Available
2 2D
3 3D
GSV-GNSS Satellites in View
Table B-8 contains the values for the following example:
$GPGSV,2,1,07,07,79,048,42,02,51,062,43,26,36,256,42,27,27,138,42*71
$GPGSV,2,2,07,09,23,313,42,04,19,159,41,15,12,041,42*41
TableB-8GSVDataFormat
Name Example Units Description
Message ID $GPGSV GSV protocol header
Number of Messages12 Range 1 to 3
Message Number11 Range 1 to 3
Satellites in View 07
Satellite ID 07 Channel 1(Range 1 to 32)
Elevation 79 degrees Channel 1(Maximum90)
Azimuth 048 degrees Channel 1(True, Range 0 to 3
5
SNR(C/No) 42 dBHz Range 0 to 99,null when not tr
a
……. …….
Satellite ID 27 Channel 4 (Range 1 to 32)
Elevation 27 Degrees Channel 4(Maximum90)
Azimuth 138 Degrees Channel 4(True, Range 0 to 3
5
SNR(C/No) 42 dBHz Range 0 to 99,null when not tr
a
Checksum *71
<CR><LF> End of message termination
Depending on the number of satellites tracked multiple messages of GSV data may be required.