USGlobalsat EM-408 User Manual

EM-408

Version 1.4.1

GPS Engine Board

EM-408

Globalsat Technology Corporation

16F., No. 186, Jian-Yi Road, Chung-Ho City, Taipei Hsien 235,
Ta iw an
Tel: [phone]/ Fax: [phone]

[e-mail]
www.globalsat.com.tw

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USGlobalSat, Inc.

14740 Yorba Court, Chino, CA 91710
Tel: [phone] / Fax: [phone]

[e-mail]
www.usglobalsat.com

Specifications are subject to be changed without notice.

EM-408

Version 1.4.1

1. Product Information



Product Part I.D. EM-408
Product Description



The EM-408 GPS engine board is low cost but maintains high reliability and accuracy making it an
ideal choice for integration with OEM/ODM systems. The EM-408 features an integrated patch
antenna for complete implementation.

 Product Features

 SiRF Star III high performance GPS chipset
 Very high sensitivity (Tracking Sensitivity: -159dBm)
 Extremely fast TTFF (Time To First Fix) at low signal levels
 Supports the NMEA 0183 data protocol
 Built-in SuperCap to maintain system data for rapid satellite acquisition
 Built-in patch antenna
 Foliage Lock for weak signal tracking
 Compact in size
 All-in-view 20-channel parallel processing
 Superior urban canyon performance
 WAAS / EGNOS support
 RoHS compliant

 Product Specifications

GPS Receiver

Chipset SiRF Star III/LP Single

Frequency L1, 1575.42 MHz

Code 1.023 MHz chip rate

Protocol Electrical Level: TTL level,

Channels 20

Output Voltage Level: 0V~2.85V
Baud Rate: 4800 bps ~ 57,600bps
(adjustable)
Output Message: NMEA 0183 GGA, GSA,
GSV, RMC (VTG, GLL optional)

Specifications are subject to be changed without notice.

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EM-408

Sensitivity -159dBm

Cold Start 42 seconds average

Warm Start 38 seconds average

Hot Start 8 second average

Reacquisition 0.1 second average

Accuracy Position: 10 meters, 2D RMS

5 meters, 2D RMS, WAAS enabled
Velocity: 0.1 ms
Time: 1µs synchronized to GPS time

Maximum Altitude 18,000 meters (60,000 feet) max

Maximum Velocity 515 meter/second (1000 knots) max

Maximum Acceleration 4G

Datum WGS-84

Jerk Limit 20m/sec **3

Physical Characteristics

Version 1.4.1

Dimensions 1.4” x 1.4” x 0.3” (36.4 x 35.4 x 8.3mm)

DC Characteristics

Power Supply 3.3V DC Input

Power Consumption 44mA (Continuous Mode)

25mA (Trickle Power Mode)

Environmental Range

Humidity Range 5% to 95% non-condensing

Operation Temperature -40F to +185F (-40C to 85C)

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Specifications are subject to be changed without notice.

2. Technical Information

 Physical Characteristics

EM-408

Version 1.4.1

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Specifications are subject to be changed without notice.

 Pin Assignment

EM-408

Version 1.4.1

 Pin Explanation

ENABLE/DISABLE: On / Off
VCC:
TX: This is the main transmit channel for outputting navigation and measurement data to user’s

_ navigation software or user-written software.

GND: GND provides the ground for the engine boards. Be sure to connect all grounds.

(DC power input) This is the main DC supply for a 3.3V power module board.

RX: This is the main receive channel for receiving software commands to the engine board from

SiRfDemo software or from user-written software. (NOTE

kept “HIGH” for operation. From Vcc connect a 470 Ohm resistor in series with a 3.2v Zener

diode to Ground. Then, connect the Rx input to Zener’s cathode to pull the input “HIGH”.)

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: When not in use this pin must be

Specifications are subject to be changed without notice.

EM-408

 Mounting

Recommended mounting methods:

a. Use industrial grade double-sided foam tape. Place it on the bottom side of the engine

board.

b. A recessed cavity in your housing design with a foam pad to eliminate shifting or movement.

c. Use provided mounting holes on the GPS engine board PCB.

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

Version 1.4.1

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 Altitude1 9.0 meters
Units M meters
Geoid Separation1 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

SiRF Technology Inc. does not support geoid corrections. Values are WGS84 ellipsoid heights.

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Specifications are subject to be changed without notice.

EM-408

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

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

Table B-5 GSA Data Format

Name Example Units Description

Message ID $GPGSA GSA protocol header

Mode1 A See Table B-6

Version 1.4.1

Mode2 3 See Table B-7

Satellite Used1 07 Sv on Channel 1

Satellite Used1 02 Sv on Channel 2

.

Satellite Used1 Sv on Channel 12

PDOP 1.8 Position dilution of Precision

HDOP 1.0 Horizontal dilution of Precision

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EM-408

5

a

5

a

VDOP 1.5 Vertical dilution of Precision

Checksum *33

<CR><LF> End of message termination

1. Satellite used in solution.

Table B-6 Mode1

Value Description

M Manual-forced to operate in 2D or 3D mode

A 2D automatic-allowed to automatically switch 2D/3D

Table B-7 Mode 2

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

Table B-8 GSV Data Format

Version 1.4.1

Name Example Units Description

Message ID $GPGSV GSV protocol header
Number of Messages1 2 Range 1 to 3
Message Number1 1 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
SNR(C/No) 42 dBHz Range 0 to 99,null when not tr
……. …….
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
SNR(C/No) 42 dBHz Range 0 to 99,null when not tr
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 B-9 contains the values for the following example:

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Specifications are subject to be changed without notice.

EM-408

Version 1.4.1

$GPRMC,161229.487,A,3723.2475,N,12158.3416,W,0.13,309.62,120598,,*10

Table B-9 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
Course Over Ground 309.62 degrees True
Date 120598 ddmmyy
Magnetic Variation2 degrees E=east or W=west
Checksum *10
<CR><LF> End of message termination
SiRF Technology Inc. does not support magnetic declination. All “course over ground” data are
Geodetic WGS48 directions.

VTG-Course Over Ground and Ground Speed
$GPVTG,309.62,T,,M,0.13,N,0.2,K*6E

Table B-9 VTG Data Format

Name Example Units Description

Message ID $GPVTG VTG protocol header
Course 309.62 degrees Measured heading
Reference T True
Course degrees Measured heading
Reference M Magnetic
Speed 0.13 knots Measured horizontal speed
Units N Knots
Speed 0.2 Km/hr Measured horizontal speed
Units K Kilometers per hour
Checksum *6E
<CR><LF> End of message termination

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Specifications are subject to be changed without notice.

EM-408

■ NMEA Input Command
A.) Set Serial Port ID:100 Set PORTA parameters and protocol

This command message is used to set the protocol (SiRF Binary, NMEA, or USER1) and/or the

communication parameters (baud, data bits, stop bits, parity). Generally, this command is utilize
to switch the GPS module back to SiRF Binary protocol mode, where an extensive message
commands are readily available. In example, whenever users are interested in altering
navigation parameters, a valid message sent and is receive by the recipient module, the new
parameters will be stored in battery backed SRAM and then the receiver will restart using the
saved parameters.

Format:
$PSRF100,<protocol>,<baud>,<DataBits>,<StopBits>,<Parity>*CKSUM
<CR><LF>

<protocol> 0=SiRF Binary, 1=NMEA, 4=USER1
<baud> 1200, 2400, 4800, 9600, 19200, 38400
<DataBits> 8,7. Note that SiRF protocol is only valid f8 Data bits
<StopBits> 0,1
<Parity> 0=None, 1=Odd, 2=Even

Example 1: Switch to SiRF Binary protocol at 9600,8,N,1
$PSRF100,0,9600,8,1,0*0C<CR><LF>
Example 2: Switch to User1 protocol at 38400,8,N,1
$PSRF100,4,38400,8,1,0*38<CR><LF>

**Checksum Field: The absolute value calculated by exclusive-OR the 8 data bits of each

character in the Sentence, between, but, excluding “$” and “*”. The hexadecimal value of the
most significant and least significant 4 bits of the result are converted to two ASCII characters
(0-9,A-F) for transmission. First, the most significant character is transmitted.

**<CR><LF> : Hex 0D 0A

B.) Navigation initialization ID:101 Parameters required for start

This command is used to initialize the GPS module for a “Warm” start, by providing real-time

position （in X, Y, Z coordinates), clock offset, and time. This action enables the GPS receiver to
search for the necessary satellite signals at the correct signal parameters. The newly acquired
and stored satellite data will enable the receiver to acquire signals more quickly, and thus,
generate a rapid navigational solution.

When a valid Navigation Initialization command is receive, the receiver will restart using the input

parameters as a basis for satellite selection and acquisition.

Format
$PSRF101,<X>,<Y>,<Z>,<ClkOffset>,<TimeOfWeek>,<WeekNo>,<chnlCount>,<ResetCfg>
*CKSUM<CR><LF>

<X> X coordinate position
INT32

Version 1.4.1

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EM-408

<Y> Y coordinate position
INT32
<Z> Z coordinate position
INT32
<ClkOffset> Clock offset of the receiver in Hz, Use 0 for last saved value if

available.

If this is unavailable, a default value of 75000 for GSP1, 95000 for

GSP 1/LX is used.
INT32
<TimeOf Week> GPS Time Of Week
UINT32
<WeekNo> GPS Week Number
UINT16
Week No and Time Of Week calculation from UTC time
<chnlCount> Number of channels to use.1-12. If your CPU throughput is not high

enough, you could decrease needed throughput by reducing the

number of active channels
UBYTE
<ResetCfg> bit mask
0×01=Data Valid warm/hotstarts=1
0×02=clear ephemeris warm start=1
0×04=clear memory. Cold start=1
UBYTE

Example: Start using known position and time.
$PSRF101,-2686700,-4304200,3851624,96000,497260,921,12,3*7F

C.) Set DGPS Port ID:102 Set PORT B parameters for DGPS input

This command is used to control Serial Port B, an input serial only port used to receive RTCM

differential corrections. Differential receivers may output corrections using different
communication parameters. The default communication parameters for PORT B are set for 9600
Baud, 8data bits, 0 stop bits, and no parity. If a DGPS receiver is used which has different
communication parameters, use this command to allow the receiver decode data correctly.
When a valid message is received, the parameters are stored in a battery backed SRAM.
Resulting, GPS receiver using the saved Parameters for restart.

Format:
$PSRF102,<Baud>,<DataBits>,<StopBits>,<Parity>*CKSUM<CR><LF>

<baud> 1200,2400,4800,9600,19200,38400
<DataBits> 8
<StopBits> 0,1
<Parity> 0=None,Odd=1,Even=2

Example: Set DGPS Port to be 9600,8,N,1
$PSRF102,9600,8,1.0*12

Version 1.4.1

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Specifications are subject to be changed without notice.

EM-408

D.) Query/Rate Control ID:103 Query standard NMEA message and/or set output rate

This command is used to control standard NMEA data output messages: GGA, GLL, GSA, GSV,

RMC, and VTG. Using this command message, standard NMEA message is polled once, or
setup for periodic output. In addition, checksums may also be enable or disable contingent on
receiving program requirements. NMEA message settings are stored in a battery-backed
memory for each entry when the message is accepted.

Format:
$PSRF103,<msg>,<mode>,<rate>,<cksumEnable>*CKSUM<CR><LF>

<msg> 0=GGA,1=GLL,2=GSA,3=GSV,4=RMC,5=VTG
<mode> 0=SetRate,1=Query
<rate> Output every <rate>seconds, off=0,max=255
<cksumEnable> 0=disable Checksum,1=Enable checksum for specified message

Example 1: Query the GGA message with checksum enabled
$PSRF103,00,01,00,01*25

Example 2: Enable VTG message for a 1Hz constant output with checksum enabled
$PSRF103,05,00,01,01*20

Example 3: Disable VTG message
$PSRF103,05,00,00,01*21

E.) LLA Navigation initialization ID:104 Parameters required to start using Lat/Lon/Alt

This command is used to initialize the GPS module for a “Warm” start, providing real-time

position (Latitude, Longitude, Altitude coordinates), clock offset, and time. This action enables
the GPS receiver to search for the necessary satellite signals at the correct signal parameters.
The newly acquired and stored satellite data will enable the receiver to acquire signals more
quickly, and thus, generate a rapid navigational solution.

When a valid LLA Navigation Initialization command is receive, then the receiver will restart

using the input parameters as a basis for satellite selection and acquisition.

Format:
$PSRF104,<Lat>,<Lon>,<Alt>,<ClkOffset>,<TimeOfWeek>,<WeekNo>,
<ChannelCount>, <ResetCfg>*CKSUM<CR><LF>

<Lat> Latitude position, assumed positive north of equator and

negative south of equator float, possibly signed

<Lon> Longitude position, it is assumed positive east of Greenwich

and negative west of Greenwich Float, possibly signed

<Alt> Altitude position float, possibly signed

Version 1.4.1

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Specifications are subject to be changed without notice.

EM-408

<ClkOffset> Clock Offset of the receiver in Hz, use 0 for last saved value if

available.

If this is unavailable, a default value of 75000 for GSP1, 95000 for

GSP1/LX is used.
INT32
<TimeOfWeek> GPS Time Of Week
UINT32
<WeekNo> GPS Week Number
UINT16
<ChannelCount> Number of channels to use. 1-12
UBYTE
<ResetCfg> bit mask
0×01=Data Valid warm/hot starts=1
0×02=clear ephemeris warm start=1
0×04=clear memory. Cold start=1
UBYTE
Example: Start using known position and time.
$PSRF104,37.3875111,-121.97232,0,96000,237759,922,12,3*37

F.) Development Data On/Off ID:105 Switch Development Data Messages On/Off
Use this command to enable development debug information if you are having trouble in

attaining commands accepted. Invalid commands will generate debug information that should
enable the user to determine the source of the command rejection. Common input rejection
problems are associated to invalid checksum or parameter out of specified range. Note, this
setting is not preserved across a module reset.

Format: $PSRF105,<debug>*CKSUM<CR><LF>
<debug> 0=Off,1=On
Example: Debug On $PSRF105,1*3E
Example: Debug Off $PSRF105,0*3F

G). Select Datum ID:106 Selection of datum to be used for coordinate transformations

GPS receivers perform initial position and velocity calculations using an earth-centered

earth-fixed (ECEF) coordinate system. Results may be converted to an earth model (geoid)
defined by the selected datum. The default datum is WGS 84 (World Geodetic System 1984)
which provides a worldwide common grid system that may be translated into local coordinate
systems or map Datum. (Local map Datum are a best fit to the local shape of the earth and not
valid worldwide.)

Examples:
Datum select TOKYO_MEAN
$PSRF106,178*32

Version 1.4.1

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EM-408

Name Example Units Description

Message ID $PSRF106 PSRF106 protocol header
Datum 178 21= WGS84

178= Tokyo_Mean
179= Tokyo_Japan
180= Tokyo_Korea

181= Tpkyo_Okinawa
Checksum *32
<CR><LF> End of message termination

Version 1.4.1

* * *

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Specifications are subject to be changed without notice.