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GPS Receiver / Module GE-2525LPX

Introduction
GE-2525LPX low power and small form factor board is the newest generation of GPS module. The module is powered by latest SiRF Star III single chip and iTrac Wireless proprietary navigation technology that provides you with stable and accurate navigation data. The smallest form factor and miniature design is the best choice to be embedded in a device such as portable navigation device, personal locator, speed camera detector and vehicle locator.

Product Features

  • 20 parallel channels
  • SMT type with stamp holes
  • TCXO design
  • 0.1 second reacquisition time
  • Small form factor with embedded SiRF Star III single chip technology.
  • NMEA-0183 compliant protocol/customize protocol.
  • Enhanced algorithm for navigation stability
  • Excellent sensitive for urban canyon and foliage environments.
  • DGPSBAS (WAAS, EGNOS and MSAS) support
  • Auto recovery while RTC crashes
  • Trickle power supported
  • Build-in LNA and saw filter

Product Applications

  • Automotive navigation
  • Personal positioning and navigation
  • Marine navigation
  • Timing application

Product Pictures
GE-2525LPX

Table 1-1 The interface board pin definition

Pin No. GE-2525LPX Pin No. GE-2525LPX
1 VCC 16 GND
2 GND 17 RF-IN
3 Bootselect 18 GND
4 RXA 19 V-ANT
5 TXA 20 VCC-RF
6 TXB 21 V-BAT
7 RXB 22 RESET-IN
8 GPIO14 23 GPIO10
9 RF-ON 24 GPIO1
10 GND 25 GPIO4
11 GND 26 GPIO0
12 GND 27 GPIO13
13 GND 28 GPIO15
14 GND 29 PPS
15 GND 30 GND

GE-2525LPX Series Block Diagram
GE-2525LPX engine board consists of SiRF star III single chipset technology;
4Mbits flash memory, and proprietary software. The system is described as follows.

  • External antenna.
  • 4 Mega bits flash memory.
  • 22 pin I/O pin.

GE-2525LPX Technical Specification
Impedance: 50Ω

Table 1-2 Technical Specifications

No Function Specification
GPS receiver
1 Chipset SiRF Star III, GSC3f/LPx
(Digital, RF in a single package)
2 Frequency L1 1575.42MHz.
3 Code C.A. Code.
4 Channels 20 parallel
5 Chip Sensitivity -159dBm.
6 Chip Cold start 35 sec @ open sky (Typical)
7 Chip Warm start 35 sec @ open sky (Typical)
8 Chip Hot start 1 sec @ open sky (Typical)
9 Reacquisition less than 1s
10 Position accuracy 10meters at 2D RMS.
11 Maximum altitude 18000 m
12 Maximum velocity 514 m/s
13 Trickle power mode Duty cycle ≤ 34%. (Variable)
14 Update rate Continuous operation: 1Hz
15 DGPS WAAS, EGNOS
Interface
16 LNA 15dB Gain. (Typical)
17 I/O Pin 30pin
Power consumption
18 Vcc DC 3.3 ±5%
19 Current Avg. 48mA@3.3V(without ext. antenna)
Environment
20 Temperature Operating : -40 ~ 85°C
Storage : -40 ~ 85°C
21 Humidity ≤95%

Application Circuit

Note:

  • Ground Planes:
    These pins (2, 10~16, 18, 30) should be connect to ground.
  • Serial Interface:
    (i) The TXA pin is the serial output data. (Default NMEA)
    (ii) The TXB pin is the serial output data (Default Null)
    (iii) The RXA pin is the serial output data (Default NMEA)
    (iv) The RXB pin is the serial input data (Default Null).
  • Backup Battery:
    When module is working, must to supply VCC_3V3(P1) and V_RTC_3V3 (P21) power at the same time. It's recommended to connect a backup battery to V_RTC_3V3 pin.
    In order to enable the warm start and hot start features of the GPS receiver.
    If you use backup battery, should be add a bypassing capacitor (10uF) at V_RTC_3V3 pin. It can reduce noise and increase the stability.
  • RF_IN:
    Connecting to the antenna has to be routed on the PCB. The transmission
    line must to be control impedance from RF_IN pin to the antenna or antenna
    connector of your choice. (Impedance 50Ω)
  • Power:
    Connect V_GPS_3V3 pin to DC +3.3V. The power supply must add bypass
    capacitor (10uF and 1uF).It can reduce the Noise from power supply and
    increase power stability.
  • Active antenna bias voltage:
    The VCC_RF_OUT pin (pin 20) is provide voltage 2.85V. If you use active
    antenna, you can connect this pin to V_ANT_IN pin (pin 19) to provide bias
    voltage of active antenna. The bias voltage will be through GPS_RF_IN pin
    to provide active antenna bias voltage from Vcc_RF_OUT pin.
    If your bias voltage of active antenna isn't 2.85V, you can input bias voltage
    to V_ANT_IN pin (pin 19). And input bias voltage of you need. The input
    bias voltage will through GPS_RF_IN pin to provide active antenna bias
    voltage from V_ANT_IN pin.
    PS:
    (1) The maximum power consumption of active antenna is about 85mW.
    (2) The input gain ranges are 19~22dB.
  • GPIO:
    The GPIO pin is recommended to connect to serial resistance(220􀓨),if use
    the GPIO function.
  • If no use GPIO functions, it doesn't connect anything.

Recommend Layout PAD:

Mechanical Layout

GE-2525LPX-Test Software Specification:

No Function Specification
1 Clock offset 88000Hz≤Test rate≤104000Hz
2 Clock Drift Test rate≤200Hz
3 C/No Hi Power Mean Test rate≤39dB
4 C/No Hi Power Sigma Test rate≤2dB
5 Bit Sync Test rate≤5 Sec
6 Frame Sync Test rate≤28 Sec
7 Phase Error Test rate≤0.22
8 RTC  
  RTC Frequency 31000≤Test rate≤33500

Reliability and quality target
MTBF > 10000 hours.

Hardware interface

Table 1-3 Definition of Pin assignment

Pin # Signal Name I/O Description Characteristics
1 VCC_3V3 I DC Supply Voltage input DC +3.3V±5%
2 GND G Ground Reference Ground
3 Bootselect I Boot mode 3.15V≥VIH ≥ 2.0V  -0.3V≥VIL ≥ 0.86V
4 RXA O Serial port A 3.15V≥VIH ≥ 2.0V  -0.3V≥VIL ≥ 0.86V
5 TXA O Serial port A 2.85V≥VOH ≥ 2.14V     VOL ≤ 0.71V
6 TXB O Serial port B 2.85V≥VOH ≥ 2.14V VOL ≤ 0.71V
7 RXB I Serial port B 3.15V≥VIH ≥ 2.0V  -0.3V≥VIL ≥ 0.86V
8 GPIO [14] I/O General
purpose I/O
3.15≥VIH ≥ 2.0V -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V  VOL ≤ 0.71V
9 RF_ON O Indicates
power state
of RF part
VOH = 2.85V  VOL = 0V
10 GND G Ground Reference Ground
11 GND G Ground Reference Ground
12 GND G Ground Reference Ground
13 GND G Ground Reference Ground
14 GND G Ground Reference Ground
15 GND G Ground Reference Ground
16 GND G Ground Reference Ground
17 RF_IN I GPS Signal input 50 Ω@1.57542GHz
18 GND G Ground Reference Ground
19 V_ANT_IN I Active
Antenna
Bias voltage
Receiving DC power supply for active antenna
bias.
20 VCC_RF_OUT O Supply
Antenna
Bias voltage
DC +2.85V ±2%
Current < 30mA
21 V_RTC_3V3 I Backup
voltage
supply
DC +2.5V~+3.6V
Current ≤ 10 uA
22 Reset I Reset
(Active low)
VIH >2.3V  VIL < 0.8V
23 GPIO[10] I/O General
Purpose I/O
3.15V≥VIH ≥ 2.0V  -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V VOL ≤ 0.71V
24 GPIO[1] I/O General
Purpose I/O
3.15V≥VIH ≥ 2.0V  -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V       VOL ≤ 0.71V
25 GPIO4 I/O General
Purpose I/O
3.15V≥VIH ≥ 2.0V -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V  VOL ≤ 0.71V
26 GPIO0 I/O General
Purpose I/O
3.15V≥VIH ≥ 2.0V -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V VOL ≤ 0.71V
27 GPIO[13] I/O General
Purpose I/O
3.15V≥VIH ≥ 2.0V -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V VOL ≤ 0.71V
28 GPIO[15] I/O General
Purpose I/O
3.15V≥VIH ≥ 2.0V -0.3V≥VIL ≥ 0.86V
2.85V≥VOH ≥ 2.14V VOL ≤ 0.71V
29 PPS O One pulse
per second
3.15V≥VIH ≥ 2.0V  -0.3V≥VIL ≥ 0.86V
30 GND G Ground Reference Ground

Definition of Pin assignment
VCC_3V3 (+3.3V DC power Input)
This is the DC power supply input pin for GPS system. It provides voltage to
module.
GND
GND provides the ground .
Boot
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.
RXB
This is the auxiliary receiving channel and is used to input differential
corrections to the board to enable DGPS navigation.
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_ON
This pin indicates state of RF voltage.
GPS_RF_IN
This pin receives GPS analog signal. The line on the PCB between the
antenna(or antenna connector) has to be a controlled impedance line
(Microstrip at 50􀓨).
V_ANT_IN
This pin is reserved as external DC power supply input for active antenna.
If using 2.85V active antenna, pin 20 has to be connected to pin 19.
If using 3.3V or 5V active antenna ,this pin has to be connected to 3.3V or 5V
power supply.
PS: The current must be ≤100mA and voltage ≤12V,if using external power
supply.
VCC_RF_OUT
This pin can provide power 30mA@2.85V for active antenna.

Reset
This pin provides an active-low reset input to the board. It causes the board to
reset and start searching for satellites. If not utilized, it may be left open.
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.
V_RTC_3V3 (Backup battery)
This is the battery backup input that powers the SRAM and RTC when main
power is removed. Typical current draw is 10uA.
The supply voltage should be between 2.5V and 3.6V.
GPIO Functions
Several I/Os are connected to the digital interface connector for custom applications.

Software Interface
NMEA Protocol
NMEA Output Messages: the Engine board outputs the following messages as shown in
Table 2-1:

Table 2-1 NMEA-0183 Output Messages

NMEA Record Description
GGA Global positioning system fixed data
GSA GNSS DOP and active satellites
GSV GNSS satellites in view
RMC Recommended minimum specific GNSS data
GLL Geographic position - latitude/longitude
VTG Course over ground and ground speed

GGA-Global Positioning System Fixed Data
Table 2 contains the values of the following example:
$GPGGA, 161229.487, 3723.2475, N, 12158.3416, W, 1, 07, 1.0, 9.0, M, , , ,0000*18

Table 2 GGA Data Format

Name Example Units Description
Message ID $GPGGA   GGA protocol header
UTC Position 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 2-1
Satellites Used 07   Range 0 to 12
HDOP 1.0   Horizontal Dilution of Precision
MSL Altitude 9.0 meters  
Units M meters  
Geoid Separation   meters  
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

Table 3 Position Fix Indicators

Value Description
0 Fix not available or invalid
1 GPS SPS Mode, fix valid
2 Differential GPS, SPS Mode, fix valid
3-5 Not Supported
6 Dead Reckoning Mode, fix valid

GSA-GNSS DOP and Active Satellites
Table 4 contains the values of the following example:
$GPGSA, A, 3, 07, 02, 26, 27, 09, 04, 15, , , , , , 1.8, 1.0, 1.5*33

Table 4 GSA Data Format

Name Example Units Description
Message ID $GPGSA   GSA protocol header
Mode 1 A   See Table 5
Mode 2 3   See Table 6
ID of Satellite Used 07   Sv on Channel 1
ID of Satellite Used 02   Sv on Channel 2
...     ...
ID of Satellite Used     Sv 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

Table 5 Mode 1

Value Description
M Manual-forced to operate in 2D or 3D mode
A Automatic-allowed to automatically switch 2D/3D

Table 6 Mode 2

Value Description
1 Fix not available
2 2D
3 3D

GSV-GNSS Satellites in View
Table 7 contains the values of 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

Table 7 GSV Data Format

Name Example Units Description
Message ID $GPGSV   GSV protocol header
Total Number of Messages1 2   Range 1 to 3
Messages Number1 1   Range 1 to 3
Satellites in View 07    
Satellite ID 07   Channel 1(Range 1 to 32)
Elevation 79 degrees Channel 1(Range 00 to 90)
Azimuth 048 degrees Channel 1(True, Range 000 to 359)
SNR (C/No) 42 dBHz Channel 1(Range 0 to 99, null when not tracking)
Satellite ID 27   Channel 4(Range 01 to 32)
Elevation 27 degrees Channel 4(Range 00 to 90)
Azimuth 138 degrees Channel 4(True, Range 000 to 359)
SNR (C/No) 42 dB-Hz Channel 4(Range 00 to 99, null when not tracking)
Checksum *71    
<CR> <LF>     End of message termination

Depending on the number of satellites tracked multiple messages of GSV data may be required.

RMC-Recommended Minimum Specific GNSS Data
Table 8 contains the values of the following example:
$GPRMC, 161229.487, A, 3723.2475, N, 12158.3416, W, 0.13, 309.62, 120598, ,*10

Table 8 RMC Data Format

Name Example Units Description
Message ID $GPRMC   RMC protocol header
UTC Time 161229.487   hhmmss.sss
Status A   A=data valid or V=data not valid
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
Speed Over Ground 0.13 knots True
Course Over Ground 309.62 degrees  
Date 120598   ddmmyy
Magnetic Variation   degrees  
Variation sense     E=east or W=west (Not shown)
Mode A   A=Autonomous, D=DGPS, E=DR
Checksum *10    
<CR><LF>     End of message termination

VTG-Course Over Ground and Ground Speed
Table 9 contains the values of the following example:
$GPVTG,79.65,T,,M,2.69,N,5.0,K,A*38

Table 9 VTG Data Format

Name Example Units Description
Message ID $GPVTG   VTG protocol header
Course over rgound 79.65 degrees Measured heading
Reference T   True
Course over ground   degrees Measured heading
Reference M   Magnetic
Speed over ground 2.69 Knots Measured speed
Units N   Knots
Speed over ground 5.0 Km/hr Measured speed
Units K   Kilometer per hour
Mode A   A-autonomous, D=DGPS, E=DR
Checksum *38    
<CR><LF>     End of message termination

GLL-Geographic Position - Latitude/Longitude
Table 10 contains the values of the following example:
$GPGLL,2503.6319,N,12136.0099,E,053740.000,A,A*52

Table 10 GLL Data Format

Name Example Units Description
Message ID $GPGLL   GLL protocol header
Latitude 2503.6319   ddmm.mmmm
N/S indicator N   N=north or S=south
Longitude 12136.0099   Dddmm.mmmm
E/W indicator E   E=east or W=west
UTC Time 053740.000   hhmmss.sss
Status A   A=data valid or V=data not valid
Mode A   A=autonomous, D=DGPS, E=DR
Checksum *52    
<CR><LF>     End of message termination

GPS Receiver User's Tip

  • GPS signal will be affected by weather and environment conditions, so it is recommended to use the GPS receiver under less shielding environments to ensure GPS receiver has better receiving performance.
  • When GPS receiver is moving, it will prolong the time to fix the position, so it is recommended to wait for the satellite signals locked at a fixed point when first power-on the GPS receiver to ensure to lock the GPS signal at the shortest time.
  • The following situation will affect the GPS receiving performance:
    • i. Solar control filmed windows.
      ii. Metal shielded, such as umbrella, or in vehicle.
      iii. Among high buildings.
      iv. Under bridges or tunnels.
      v. Under high voltage cables or near by radio wave sources, such as mobile phone base stations.
      vi. Bad or heavy cloudy weather.
  • If the satellite signals can not be locked or encounter receiving problem (while in the urban area), the following steps are suggested:
    • i. Please plug the external active antenna into GPS receiver and put the antenna on outdoor or the roof of the vehicle for better receiving performance.
      ii. Move to another open space or reposition GPS receiver toward the direction with less blockage.
      iii. Move the GPS receiver away from the interferences resources.
      iv. Wait until the weather condition is improved.
  • While a GPS with a backup battery, the GPS receiver can fix a position immediately at next power-on if the build-in backup battery is full-recharged.

Package Specification and Order Information
Shipment Method: Tape and reel

Lead-Free Standard Reflow