Bluetooth GPS Tracer

一個簡單有趣的 GPS 應用，可以拿來用在尋機…

結合現成的三種模組 GPS Module、HC12 RF Module、HC-05 Bluetooth Module 再加上簡單的 App 解 MNEA GPS 格式，就能實現遠距 GPS 追蹤，類似防丟器的概念，但即時距離可達 1 公里。

Combine "CRIUS GPS Module"、"HC12 - Long Range RF Wireless SERIAL Module" and "HC-05 Bluetooth Module"，make remote location trace with 433mhz RF and Bluetooth comunication

App...
https://play.google.com/store/apps/details?id=com.longfellowchen.bluetoothgpstracer

系統架構 - System Architecture…
GPS--[UART]-->HC12-->~~[RF433MHZ]~~-->HC12-->HC-05-->~~[BT2.4G]-->SmartPhone

硬體線路 - Hardware circuit...
基本上只是把模組 UART 線路全串在一起…

Remote device...
GPS-TX ---------------->HC12-RX
GPS-RX ---------------->HC12-TX (option)

Local device
HC05-TX ---------------->HC12-RX(option)
HC05-RX ---------------->HC12-TX

All Module..
VCC ----------------> +5V
GND ----------------> GND

注意事項…
*All module should set the same baud-rate (default is 9600)
*HC12 Module can set transmit power to what you want. (see it's documents)

Convert NMEA format data to latitude and longitude for GMap Latlng

Reference...

http://aprs.gids.nl/nmea/

Format...

$GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,ddmmyy,x.x,a*hh

1    = UTC of position fix

2    = Data status (V=navigation receiver warning)

3    = Latitude of fix

4    = N or S

5    = Longitude of fix

6    = E or W

7    = Speed over ground in knots

8    = Track made good in degrees True

9    = UT date

10   = Magnetic variation degrees (Easterly var. subtracts from true course)

11   = E or W

12   = Checksum

Formula...

Latitude / Longitude = ddmm.mmmm = dd + (mm.mmmm/60) (* -1 for W and S)

Java code...

String str = "$GPRMC,182807.036,A,3731.9404,N,10601.6986,W,0.078542,40.74,050107,,*20"

if( str.startsWith( "$GPRMC" ) )

{

    String[] tags = str.split(",");

    if( tags[2].equals("A") ) {

        String lotdd = tags[3].substring( 0, tags[3].indexOf(".") - 2 );

        String lotmm = tags[3].substring( tags[3].indexOf(".") -2 );

        float lot = Float.valueOf( lotdd ) + Float.valueOf( lotmm )/60;

        if( tags[4].equals("S") )

            lot = -lot;

        String lngdd = tags[5].substring( 0, tags[5].indexOf(".") - 2 );

        String lngmm = tags[5].substring( tags[5].indexOf(".") -2 );

        float lng = Float.valueOf( lngdd ) + Float.valueOf( lngmm )/60;

        if( tags[6].equals("W") )

            lng = -lng;

        LatLng pos = new LatLng( lot, lng );

    } else {

        // Invalid $GPRMC

    }

}