View source for B0.8051 Interfacing GPS ← B0.8051 Interfacing GPS

[[Category:8051 tutorials]]
The Global Positioning System (GPS) is a satellite-based navigation system that provides location and time information of the GPS device in all weather conditions, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites.<br>
A GPS module is a device that uses Global Positioning System to determine the location of a vehicle or person. GPS receivers are used to provide reliable navigation, positioning and timing services to the users at anytime and anywhere on the earth.  This Global positioning system uses a minimum of 4 satellites to provide the data to the receivers. If the GPS receiver is only able to get signals from 3 satellites, you can still get your position, but it will be less accurate. As mentioned above, the GPS receiver needs 4 satellites to determine the position in 3-dimensions.

[[File:0Gps.png]]

=GPS Module Specs=
{| class="table table-striped table-hover table-condensed table-bordered"
|-class="info"
|Name || Description
|-
|Volatge || Vmin=3.6v and Vmax=6v (Tested with 5v)
|-
|Time To Start || Cold Start 29s(Average under Open Sky)<br>
Warm Start 28s(Average under Open Sky)<br>
Hot Start 1s(Average under Open Sky)<br>
<b>InDoor: GPS modules take more time to get valid data and some times won't work.</b>
|-
|Interface || Full Duplex Serial Interface(UART)
|-
|Baud Rate || Default-9600, Also supports 4800/9600/38400/115200
|-
|Start Bit || 1-bit
|-
|Stop Bit || 1-bit
|-
|Data Bits || 8-bit
|-
|Parity || None
|-
|Update Rate || Default 1Hz, Also supports 1/2/4/5/8/10
|-
|Ouput Frames|| GPGGA, GPGSA, GPGSV, GPRMC and GPVTG
|}

=GPS Frame Formats=
The serial interface protocol is based on the National Marine Electronics Association’s NMEA 0183 ASCII
interface specification.
[[File:GpsLog.png]]

===GGA-GLOBAL POSITIONING SYSTEM FIX DATA===
Time, position and fix related data for a GPS receiver.
<b>$GPGGA,hhmmss.sss,ddmm.mmmm,a,dddmm.mmmm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh<CR><LF></b>

===GLL - LATITUDE AND LONGITUDE, WITH TIME OF POSITION FIX AND STATUS===
Latitude and longitude of current position, time, and status.
<b>$GPGLL,ddmm.mmmm,a,dddmm.mmmm,a,hhmmss.sss,A,a*hh<CR><LF></b>

===GSA - GPS DOP AND ACTIVE SATELLITES===
GPS receiver operating mode, satellites used in the navigation solution reported by the GGA or GNS sentence
and DOP values.<br>
<b>$GPGSA,A,x,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,x.x,x.x,x.x*hh<CR><LF></b>

===GSV - GPS SATELLITE IN VIEW===
Numbers of satellites in view, PRN number, elevation angle, azimuth angle, and C/No. Four satellites details
are transmitted per message. Additional satellite in view information is sent in subsequent GSV messages.
<b>$GPGSV,x,x,xx,xx,xx,xxx,xx,…,xx,xx,xxx,xx *hh<CR><LF></b>

===RMC - RECOMMENDED MINIMUM SPECIFIC GPS/TRANSIT DATA===
Time, date, position, course and speed data provided by a GNSS navigation receiver.
<b>$GPRMC,hhmmss.sss,A,dddmm.mmmm,a,dddmm.mmmm,a,x.x,x.x,ddmmyy,x.x,a,a*hh<CR><LF></b>

===VTG - COURSE OVER GROUND AND GROUND SPEED===
The Actual course and speed relative to the ground.
<b>$GPVTG,x.x,T,x.x,M,x.x,N,x.x,K,a*hh<CR><LF></b>

=GPRMC Frame Decoding=
We will be using this frame for GPS data (time, lat-long). Below table provides the informtion encoded in the GPS frame.
$GPRMC,hhmmss.sss,A,dddmm.mmmm,a,dddmm.mmmm,a,x.x,x.x,ddmmyy,x.x,a,a*hh<CR><LF>
$GPRMC,110831.000,A,1304.8763,N,07733.6457,E,0.79,303.84,010116,,,A*68
{| class="table table-striped table-hover table-condensed table-bordered"
|-class="info"
|Field || Name || Data || Description
|-
|1 || UTC Time || 110831.000 || UTC Time in hhmmss.sss format (000000.000 - 235959.999)
|-
|2 || Status || A || Data Validity A-Valid, V-Invalid(Navigation Warning)
|-
|3 || Latitude || 1304.8763 || Latitude in dddmm.mmmm format, leading zeros transmitted
|-
|4 || N/S Indicator || N || Latitude hemisphere indicator, N-North S-South
|-
|5 || Longitude || 07733.6457 || Longitude in dddmm.mmmm format, leading zeros transmitted
|-
|6 || E/W Indicator || E || Longitude hemisphere indicator, E-East W-West
|-
|7 || Speed Over Ground || 0.79 || Speed Over Ground in Knots (000.0 ~ 999.9)
|-
|8 || Course Over Ground || 303.84 || Course Over Ground in degrees (000.0 ~ 359.9)
|-
|9 || UTC Date || 010116 || UTC Date in ddmmyy format
|-
|10 || Magnetic variation ||  || Magnetic variation in degrees(000.0 ~ 180.0)
|-
|11 || Magnetic variation ||  || Magnetic variation Direction, E-East W-West
|-
|12 || Mode Indicator || A || N - Data Not Valid<br> 
A - Autonomous Mode<br> 
D - Differential Mode<br> 
E - Estimated Mode<br> 
M - Manual Input Mode<br> 
S - Simulator Mode
|-
|13 || Checksum || 68 ||  
|}

Below is the sample code to decode the above frame
<html><script src="https://gist.github.com/SaheblalBagwan/1f78f20eb0d06df4de176f28a51dafae.js"></script></html>

=Code=
Below is the sample code to receive the GPS data, decode it and display it on LCD.
<html><script src="https://gist.github.com/SaheblalBagwan/e3f2566c938d51c050deca7aca0027c0.js"></script></html>

=Track on Google Maps=
Lat = 1304.8763,N = 13+(04.8763/60) = 13.0812716666666667<br>
Long = 07733.6457,E = 77+(33.6457/60) = 77.560761666666667<br>
Now lets paste these values <b>13.0812716666666667, 77.560761666666667</b> on google maps and track the location.
<br><br>
[[File:GpsMap.PNG]]