NEX ROBOTICS MT3318 Manual de usuario
GPS Receiver MT3318
NEX Robotics Pvt. Ltd. 1
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GPS Receiver MT3318
Figure 1: GPS Receiver MT3318 top and bottom view
Introduction
GPS Receiver MT3318 is based on the MediaTek MTK MT3318 chipset. It has active
patch antenna from Cirocomm. It can track 51 satellites simultaneously. This GPS
receiver gives data output in standard NMEA format with update rate of 1 second at 9600
bps. Receiver has onboard battery for memory backup for quicker acquisition of GPS
satellites. Receiver has 8 pin male berg connector with 2mm pitch. 8 pin female berg
connector comes with this GPS module for external connections.
Note: You may also require general purpose PCB with 2mm pitch for mounting the
receiver on the PCB.
Specifications
•Supply: 3.3V, 45mA
•Chipset: MTK MT3318
•Antenna: High gain GPS patch antenna from Cirocomm
•Data output: CMOS UART interface at 3.3V
•Protocol: NMEA-0183@9600bps (Default) at update rate of 1 second.
•Protocol message support: GGA, GSA, GSV,RMC, VTG
•No. of Satellite simultaneously tracked: 51
•Tracking Sensitivity: On-module antenna : -157 dBm
•Position Accuracy : <3 m
•Max. Update Rate：5Hz (Default: 1 Hz)
•Time to First Fix (Open sky and stationary position)
oObscuration recovery: 0.1 second average
oHot start: <1 seconds average
oWarm start: <34 seconds average
oCold start: <36 seconds average
•Size: 26mm x 26mm x11.7mm
GPS Receiver MT3318
NEX Robotics Pvt. Ltd. 2
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Kit Contains:
•GPS Receiver MT3318
•8 pin Female berg connector with 2mm pitch
•Documentation CD with terminal software from the NEX Robotics and GPS
Cockpit NMEA terminal software
GPS Receiver MT3318
NEX Robotics Pvt. Ltd. 3
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Mechanical Dimension:
Figure 2: Mechanical Dimensions
Figure 3: Inside view of the GPS receiver
GPS Receiver MT3318
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GPS Receiver MT3318 is also available in the following form factors
GPS Receiver MT3318 Module
GPS Receiver is soldered on the PCB with 3.3V low drop voltage regulator, 5V to 3.3V
logic level converter, LEDs for TX, RX and Power.
GPS Receiver MT3318 USB Module
By using this you can be directly interfaced GPS with the PC via USB port. GPS
Receiver is soldered on the PCB with 3.3V low drop voltage regulator, 5V to 3.3V logic
level converter, LEDs for TX, RX and Power has onboard USB module
Connections
GPS receiver has 8pin male berg connector with 2mm pitch for the connections. Table 1
shows the pin connections.
VCC (Pin1) 3.3V DC Supply voltage
GND (Pin2) Ground
RX (Pin3) Receiver pin (on this pin give data from external circuit)
TX (Pin4) Transmitter pin (on this pin get data from satellite)
V-ANT (Pin5) 3.3V DC Supply for external antenna
GND(Pin6) Ground
RESET(Pin7) Please keep no connection (N/C) it remain high when power is on
EXANT(Pin8) External Antenna input pin
Table 1: GPS Receiver MT3318 pin connections
You can use 8 pin female berg connector with 2mm pitch for connections which comes
with the GPS receiver.
Interfacing Microcontroller which is working on 3.3V with the GPS receiver:
Microcontroller interfacing at 3.3V is fairly strait forward process. All you have to do
connect TXD of the uC to RXD of the GPS and RXD of the uC to TXD of the GPS
receiver. And give common ground.
Figure 4: GPS interfacing with the microcontroller at 3.3V logic level
GPS Receiver MT3318
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Interfacing Microcontroller which is working on 5V with the GPS receiver:
Figure 5: GPS interfacing with the microcontroller at 5V logic level
In this case microcontroller is working at 5V while GPS receiver is operating at 3.3V.
TXD pin of the microcontroller will have 5V logic level while RXD pin of the GPS will
be operating at 3.3V. We need to use voltage divider network of the resistors to scale
down voltage level of TXD pin of the microcontroller to less than 3.3V.Figure 5 shows
voltage divider network consist of 2.2K ohm and 4.7K ohm resistors which scales down
5V approximately by the factor of 2/3
TXD pin of the GPS receiver can be directly connected to the microcontroller’s RXD pin.
Also connect common ground between both of the devices.
GPS Receiver MT3318
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Acquiring the GPS data:
GPS data can be received by the microcontroller or on the PC using any terminal
software. Following example shows the GPS data acquisition on the PC using terminal
software from the NEX Robotics.
If you are using Serial terminal from NEX Robotics then follow bellow steps
Step1: Install the terminal software from NEX Robotic on the PC which is located in the
documentation CD.
Step 2: Select COM Port in serial terminal setting column.
Step 3: Set Baud rate to 9600
Step 4: Set parity to none, Data bits to 8 and stop bits to one.
Step 5: click on connect button for connection
Connecting GPS module with the PC:
Connect GPS module with the PC using Serial port via MAX232 or equivalent TTL to
RS232 converter or using any USB to Serial Converter.
Note: If you are using USB to Serial Converters from NEX Robotics then for installing
drivers, refer to the respective product manuals.
GPS data accusation on the PC:
When GPS module inside the room:
Figure 6
GPS Receiver MT3318
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Figure 6 shows data when GPS module inside the room. You will not get any data also it
will not detect any satellite inside the room.
When GPS module outside the room:
Figure 7
Figure 7shows data when GPS module outside the room. You will get perfect data in
NMEA-0183 format at 9600bps.
GPS Receiver MT3318
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You can also use GPS Cockpit software to see GPS Data on PC
Figure 8
GPS Receiver MT3318
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GPS Cockpit software is very easy software for GPS data study. It shows GPS data in
different windows. Like you can directly get latitude and longitude on GPS information
window, you can also find out distance between two points in survey window. In signal
quality window displays the signal to noise ratio or carrier to noise. You can also see
satellite position in sky view window.All other important GPS data you can see it on
NMEA terminal window.
Install the GPS Cockpit software on the PC which is located in the documentation CD.
First Set com port and baud rate 9600 in sitting option. Then click Play NMEA file option
Figure 8 shows NMEA cock pit terminal window it having
1:- NMEA Terminal window
2:- Signal quality window
3:- GPS information window
4:- Sky view window
5:- Survey view window
For more information about Cockpit software you can Refer GPS Cockpit user manual
located in the documentation CD.
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NMEA protocol explanation:
1: GPGGA - Global Positioning System Fix Data
2: GPGSA - GPS DOP and active satellites
3: GPGSV - GPS Satellites in view
4: GPRMC: Recommended minimum specific GPS/Transit data
5: GPVTG: Track Made Good and Ground Speed.
GPGGA: Global Positioning System Fix Data
Name Example
Data Description
Sentence Identifier $GPGGA Global Positioning System Fix Data
Time 170834 17:08:34 Z
Latitude 4124.8963, N 41d 24.8963' N or 41d 24' 54" N
Longitude 08151.6838,
W 81d 51.6838' W or 81d 51' 41" W
Fix Quality:
- 0 = Invalid
- 1 = GPS fix
- 2 = DGPS fix
1 Data is from a GPS fix
Number of Satellites 05 5 Satellites are in view
Horizontal Dilution of Precision
(HDOP) 1.5 Relative accuracy of horizontal position
Altitude 280.2, M 280.2 meters above mean sea level
Height of geoid above WGS84
ellipsoid -34.0, M -34.0 meters
Time since last DGPS update blank No last update
DGPS reference station id blank No station id
Checksum *75
Used by program to check for transmission
errors
Courtesy of Brian McClure, N8PQI.
Global Positioning System Fix Data. Time, position and fix related data for a GPS receiver.
eg2. $--GGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx
hhmmss.ss = UTC of position
llll.ll = latitude of position
a = N or S
yyyyy.yy = Longitude of position
a = E or W
x = GPS Quality indicator (0=no fix, 1=GPS fix, 2=Dif. GPS fix)
xx = number of satellites in use
x.x = horizontal dilution of precision
x.x = Antenna altitude above mean-sea-level
