Make Your Own GPS Transmitter with the HC-12 Transceiver

November 10, 2016 by Mark Hughes

Create a tracking device with an HC-12 transceiver, a GPS module, an Arduino, and Google Maps.

The first article in this two-part series, Understanding and Implementing the HC-12 Wireless Transceiver Module, uses the HC-12 to create long-distance data transmission between two Arduino Unos. This article uses a pair of HC-12 transceivers, a GPS module, an Arduino, and Google Maps to create a very simple tracking device.

Item	Cost	More Information
HC-12 transceiver (x2)	$4	Datasheet
GPS Receiver	$16	Datasheet
or Adafruit GPS Logger Shield	$45	Project Guide
Arduino Uno R3 (or compatible)	$45	Reference

Part one of this two-part series discussed the HC-12 transceiver module and described how to hook it up to an Arduino and a power source.

In this article, we will create a remote GPS receiver that can be used to track nearby items without using a cellular network.

For further information on the transceiver module, please see the HC-12 datasheet (PDF).

Adding and Transmitting GPS

The Global Positioning System (GPS) allows users to accurately determine the location of objects on or above the surface of the Earth. Both of the GPS receivers listed at the top of this article transmit National Marine Electronics Association (NMEA) sentences that provide information that includes latitude and longitude, altitude, time, bearing, speed, and a great many other variables at 9600 baud.

The HC-12s can transmit the information from a GPS receiver with no additional programming or circuitry.

You can transmit GPS coordinates to remote locations with as little as a GPS receiver, an HC-12 transceiver, and a battery. Remotely transmitted coordinates would have to be received by another HC-12 transceiver and then processed with a microcontroller or computer.

A simple setup such as the one above would allow you to create a small remote object tracker; it will alert you if the object leaves a predefined area, and then you will have a certain amount of time to track the object before the transmitter goes out of range. You could use this with a vehicle, a pet, or even—if you are concerned about theft—the giant pumpkin that you are growing for the state fair.

If you are in an area with clear line of sight, the transmitters will broadcast up to one kilometer, which is a 15-minute walk (or 5-minute run). The maximum range in urban areas will decrease but should remain adequate to alert you if your luggage is leaving the train station without you, or let you know where your dog ventures when he escapes from your yard.

We can refine this project by passing the GPS data to an Arduino instead of directly to the HC-12. Then, only selected strings can be transmitted to the HC-12. This is useful if you want to increase the range of the HC-12 communication by decreasing the over-the-air baud rate.

The $16 SparkFun GPS module has a default transmission rate of 9600 baud, and this corresponds to an over-the-air rate of 15000 baud. Sending the 9600 baud GPS data to the Arduino and then transmitting only selected information to the HC-12 at 2400 baud will reduce the over-the-air rate to 5000 baud. According to the datasheet, this improves receiver sensitivity by at most 5 dB, which provides a modest increase in range.

The SparkFun GPS receiver provides six sentences at 9600 baud: GPRMC, GPVTG, GPGGA, GPGSA, GPGSV, and GPGLL.

The GPS shield from Adafruit, which is significantly more expensive, can be programmed to transmit select sentences at all standard baud rates.

This is an example data transmission from the receiver to an Arduino. You can decode your own strings with this online tool.

$GPRMC,210154.00,A,3358.88969,N,11756.33387,W,0.824,,200916,,,A*6F
$GPVTG,,T,,M,0.824,N,1.527,K,A*2C
$GPGGA,210154.00,3358.88969,N,11756.33387,W,1,05,1.67,254.3,M,-32.6,M,,*6E
$GPGSA,A,3,13,05,21,18,29,,,,,,,,3.15,1.67,2.66*01
$GPGSV,3,1,11,05,20,044,23,10,10,223,,13,26,083,22,15,37,120,*70
$GPGSV,3,2,11,16,11,322,,18,45,224,23,20,76,043,,21,55,312,22*76
$GPGSV,3,3,11,25,23,195,17,26,27,298,,29,72,108,17*47
$GPGLL,3358.88969,N,11756.33387,W,210154.00,A,A*74

Arduino libraries exist that enable decoding of NMEA sentences into the latitude & longitude pairs below:

Type	UTC Time	Position	Speed	Altitude	HDOP, VDOP, PDOP	Satellites
RMC	2016-09-20T21:01:54Z	33°58'53.38''N, 117°56'20.03''W	0.824 knots
VTG			0.824 knots
GGA	2016-09-20T21:01:54Z	33°58'53.38''N, 117°56'20.03''W		254.3		5
GSA					1.67, 2.66, 3.15	5
GSV						11
GSV						11
GSV						11
GLL	2016-09-20T21:01:54Z	33°58'53.38''N, 117°56'20.03''W

RMC (recommended minimum information), GGA (3D location and accuracy), and GLL (latitude and longitude) all include latitude, longitude, and time. GGA provides altitude, and GSA provides the dilution of precision of the reading (lower numbers indicate greater precision).

The following program is backward-compatible with the two programs presented in part one. It reads the NMEA sentences sent by the GPS to the Arduino, discards all but the selected sentence, and transmits the selected sentence to a remote Arduino when requested. It works with either the SparkFun GPS receiver or the Adafruit GPS logger shield, as shown below. This program allows users to remotely "ping" distant transceivers to determine their location.

GPS data from a remote transmitter received, via a pair of HC-12 transceivers, by a local Arduino

HC-12 transceiver paired with an Adafruit GPS shield

HC-12 transceiver paired with a SparkFun GPS module

Connect the power supply, GPS, Arduino, and HC-12 as shown above.

The SparkFun GPS receiver has only three wires; the fourth signal (GPS RXD) is not needed for basic functionality and is not made available to the user. However, if you use the Adafruit shield, the GPS RX pin is enabled, and you can change the refresh rate and which sentences the GPS transmits, eliminating the need for the portion of the Arduino code at the end of the file that simply deletes unwanted sentences.

One potential problem with using the Arduino UNO for this program is that the SoftwareSerial library can only "listen" to one serial port at a time—data sent to a serial port when the software isn't "listening" on that port will be discarded. The program functions as intended during testing, but I would not consider it a robust solution. If you need multiple serial communication ports in your project, consider the Arduino Mega, or a separate chip such as the ATSAMD21.

If you are tracking a single object near your house, it is sufficient to set upper and lower limits for expected latitude and longitude values. If you are trying to determine the distance between two GPS units, you might consider implementing Vincenty's formula on a 16-bit or 32-bit microcontroller.

/*  HC12 Send/Receive Example Program 3
    By Mark J. Hughes
    for AllAboutCircuits.com

    This code will automatically detect commands as sentences that begin
    with AT and both write them and broadcast them to remote receivers
    when requested.  Changing settings on a local transceiver will also
    change settings on a remote receiver.

    Connect HC12 "RXD" pin to Arduino Digital Pin 4
    Connect HC12 "TXD" pin to Arduino Digital Pin 5
    Connect HC12 "Set" pin to Arduino Digital Pin 6

    Connect GPS GND and 3.3V to Arduino or separate supply
    Connect GPS "RX" to Arduino Digital Pin 7 (optional)
    Connect GPS "TX" to Arduino Digital Pin 8

    Do not power over USB.  Per datasheet, power the HC12 
    with a supply of at least 100 mA current capability, and
    include a 22 uF - 1000 uF reservoir capacitor.
    
    Upload code to two Arduinos connected to two computers.

    Transceivers must be at least several meters apart to work in default mode.

*/

#include 

//--- Begin Pin Declarations ---//
const byte HC12RxdPin = 4;                          // "RXD" Pin on HC12
const byte HC12TxdPin = 5;                          // "TXD" Pin on HC12
const byte HC12SetPin = 6;                          // "SET" Pin on HC12
const byte  GPSRxdPin = 7;                          // "RXD" on GPS (if available)
const byte  GPSTxdPin = 8;                          // "TXD" on GPS
//--- End Pin Declarations ---//

//--- Begin variable declarations ---//
char byteIn;                                        // Temporary variable
String HC12ReadBuffer = "";                         // Read/Write Buffer 1 -- Serial
String SerialReadBuffer = "";                       // Read/Write Buffer 2 -- HC12
String GPSReadBuffer = "";                          // Read/Write Buffer 3 -- GPS

boolean serialEnd = false;                          // Flag for End of Serial String
boolean HC12End = false;                            // Flag for End of HC12 String
boolean GPSEnd = false;                             // Flag for End of GPS String
boolean commandMode = false;                        // Send AT commands to remote receivers
boolean GPSLocal = true;                            // send GPS local or remote flag
//--- End variable declarations ---//

// Create Software Serial Ports for HC12 & GPS
// Software Serial ports Rx and Tx are opposite the HC12 Rxd and Txd
SoftwareSerial HC12(HC12TxdPin, HC12RxdPin);
SoftwareSerial GPS(GPSTxdPin, GPSRxdPin);

void setup() {

  HC12ReadBuffer.reserve(82);                       // Reserve 82 bytes for message
  SerialReadBuffer.reserve(82);                     // Reserve 82 bytes for message
  GPSReadBuffer.reserve(82);                        // Reserve 82 bytes for longest NMEA sentence

  pinMode(HC12SetPin, OUTPUT);                      // Output High for Transparent / Low for Command
  digitalWrite(HC12SetPin, HIGH);                   // Enter Transparent mode
  delay(80);                                        // 80 ms delay before operation per datasheet
  Serial.begin(9600);                               // Open serial port to computer at 9600 Baud
  HC12.begin(9600);                                 // Open software serial port to HC12 at 9600 Baud
  GPS.begin(9600);                                  // Open software serial port to GPS at 9600 Baud
  HC12.listen();                                    // Listen to HC12
}

void loop() {
  while (HC12.available()) {                        // If Arduino's HC12 rx buffer has data
    byteIn = HC12.read();                           // Store each character in byteIn
    HC12ReadBuffer += char(byteIn);                 // Write each character of byteIn to HC12ReadBuffer
    if (byteIn == '\n') {                           // At the end of the line
      HC12End = true;                               // Set HC12End flag to true.
    }
  }

  while (Serial.available()) {                      // If Arduino's computer rx buffer has data
    byteIn = Serial.read();                         // Store each character in byteIn
    SerialReadBuffer += char(byteIn);               // Write each character of byteIn to SerialReadBuffer
    if (byteIn == '\n') {                           // At the end of the line
      serialEnd = true;                             // Set serialEnd flag to true.
    }
  }

  while (GPS.available()) {
    byteIn = GPS.read();
    GPSReadBuffer += char(byteIn);
    if (byteIn == '\n') {
      GPSEnd = true;
    }
  }

  if (serialEnd) {                                  // Check to see if serialEnd flag is true
    if (SerialReadBuffer.startsWith("AT")) {        // Check to see if a command has been sent
      if (SerialReadBuffer.startsWith("AT+B")) {    // If it is a baud change command, delete it immediately
        SerialReadBuffer = "";
        Serial.print("Denied: Changing HC12 Baud does not change Arduino Baudrate");
      }
      HC12.print(SerialReadBuffer);                 // Send local command to remote HC12 before changing settings
      delay(100);                                   //
      digitalWrite(HC12SetPin, LOW);                // If true, enter command mode
      delay(100);                                   // Delay before writing command
      HC12.print(SerialReadBuffer);                 // Send command to HC12
      Serial.print(SerialReadBuffer);               // Send command to serial
      delay(500);                                   // Wait 0.5s for reply
      digitalWrite(HC12SetPin, HIGH);               // Exit command / enter transparent mode
      delay(100);                                   // Delay before proceeding
    }
    if (SerialReadBuffer.startsWith("GPS")) {
      HC12.print(SerialReadBuffer);
      GPS.listen();
      GPSLocal = true;
    }
    HC12.print(SerialReadBuffer);                   // Send text to HC12 to be broadcast
    SerialReadBuffer = "";                          // Clear buffer 2
    serialEnd = false;                              // Reset serialEnd flag
  }

  if (HC12End) {                                    // If HC12End flag is true
    if (HC12ReadBuffer.startsWith("AT")) {          // Check to see if a command was received
      digitalWrite(HC12SetPin, LOW);                // If true, enter command mode
      delay(40);                                    // Delay before writing command
      HC12.print(HC12ReadBuffer);                   // Send incoming command back to HC12
      Serial.println(HC12ReadBuffer);               // Send command to serial
      delay(1000);                                  // Wait 0.5s for reply
      digitalWrite(HC12SetPin, HIGH);               // Exit command / enter transparent mode
      delay(80);                                    // Delay before proceeding
      HC12.println("Remote Command Executed");
    }
    if (HC12ReadBuffer.startsWith("GPS")) {
      GPS.listen();
      HC12.print("Remote GPS Command Received");
      GPSLocal = false;
    }
    Serial.print(HC12ReadBuffer);                   // Send message to screen
    HC12ReadBuffer = "";                            // Empty Buffer
    HC12End = false;                                // Reset Flag
  }

  if (GPSEnd) {
    // Options include GPRMC, GPGGA, GPGLL, etc...
    if (GPSReadBuffer.startsWith("$GPGGA")) {       // Look for target GPS sentence
      if (GPSLocal) {
        Serial.print("Local  GPS:");                // Send to local serial port
        Serial.print(GPSReadBuffer);                // Send local GPS
      } else {
        HC12.print("Remote GPS:");                  // Local Arduino responds to remote request
        HC12.print(GPSReadBuffer);                  // Sends local GPS to remote
      }
      GPSReadBuffer = "";                           // Delete target GPS sentence
      HC12.listen();                                // Found target GPS sentence, start listening to HC12 again
    } else {
      GPSReadBuffer = "";                           // Delete unwanted strings
    }
    GPSEnd = false;                                 // Reset GPS
  }
}

Data that you collect can be converted into KML files for use in Google Maps using one of many free online converters.  

 



 

The above image shows variations in the logged GPS coordinates of a stationary object. The error is rather large, even for the low-cost setup used in this project—the GPS receiver sold by SparkFun, for example, claims to provide positional accuracy of 2.5 m CEP. It is likely that multipath interference made a significant contribution to the additional error.

Real-Time GPS Tracking in Google Earth

Now we will create a GPS tracker with the HC-12 and Google Earth Pro. Through experimentation, I found that tracking worked if at least the $GPGGA, $GPGSA, and $GPGLL strings were passed along to Google Earth.  

The program below transmits GPS data to a remote receiver for tracking of remote objects. It receives all sentences at 9600 baud from the computer and then transmits just the $GPRMC, $GPGGA, and $GPGGL sentences at 4800 baud through the HC-12. A separate HC-12/Arduino pair would be needed to receive the information and transmit it to the computer.

/*  HC12 Send/Receive Example Program 4
    By Mark J. Hughes
    for AllAboutCircuits.com

    Connect HC12 "RXD" pin to Arduino Digital Pin 4
    Connect HC12 "TXD" pin to Arduino Digital Pin 5
    Connect HC12 "Set" pin to Arduino Digital Pin 6

    Connect GPS "TXD" to Arduino Digital Pin 7 (Optional)
    Connect GPS "RXD" to Arduino Digital Pin 8

    Do not power over USB.  Per datasheet, power the HC12 
    with a supply of at least 100 mA current capability, and
    include a 22 uF - 1000 uF reservoir capacitor.
    
    Upload code to two Arduinos connected to two computers.

    Transceivers must be at least several meters apart to work in default mode.

*/

#include &let;SoftwareSerial.h>

//--- Begin Pin Declarations ---//
const byte HC12RxdPin = 4;                // "RXD" Pin on HC12
const byte HC12TxdPin = 5;                // "TXD" Pin on HC12
const byte HC12SetPin = 6;                // "SET" Pin on HC12
const byte  GPSTxdPin = 7;                // "TXD" on GPS (if available)
const byte  GPSRxdPin = 8;                // "RXD" on GPS
//--- End Pin Declarations ---//

//--- Begin variable declarations ---//
char GPSbyteIn;                              // Temporary variable
String GPSBuffer3 = "";                      // Read/Write Buffer 3 -- GPS

boolean debug = false;
boolean HC12End = false;                  // Flag for End of HC12 String
boolean GPSEnd = false;                   // Flag for End of GPS String
boolean commandMode = false;              // Send AT commands to remote receivers
//--- End variable declarations ---//

// Create Software Serial Ports for HC12 & GPS
// Software Serial ports Rx and Tx are opposite the HC12 Rxd and Txd
SoftwareSerial HC12(HC12TxdPin, HC12RxdPin);
SoftwareSerial GPS(GPSRxdPin, GPSTxdPin);

void setup() {
  buffer3.reserve(82);                    // Reserve 82 bytes for longest NMEA sentence

  pinMode(HC12SetPin, OUTPUT);            // Output High for Transparent / Low for Command
  digitalWrite(HC12SetPin, HIGH);         // Enter Transparent mode
  delay(80);                              // 80 ms delay before operation per datasheet
  HC12.begin(4800);                       // Open software serial port to HC12
  GPS.begin(9600);                        // Open software serial port to GPS
  GPS.listen();
}

void loop() {
  while (GPS.available()) {
    byteIn = GPS.read();
    buffer3 += char(byteIn);
    if (byteIn == '\n') {
      GPSEnd = true;
    }
  }

  if (GPSEnd) {
    // GPRMC, GPVTG, GPGGA, GPGSA, GPGSV, GPGLL
    if (buffer3.startsWith("$GPRMC")||buffer3.startsWith("$GPGGA")||buffer3.startsWith("$GPGLL")) {
      HC12.print(buffer3);                // Transmit RMC, GGA, and GLL sentences
      buffer3 = "";                       // Clear buffer
    } else {
      buffer3 = "";                       // Delete GSA, GSV, VTG sentences
    }
    GPSEnd = false;                       // Reset GPS flag
  }
}

Here are the steps you'll need to follow:


	Open Google Earth
	Select Tools -> GPS
	Select the Realtime tab and click Start. Google Earth will cycle through available serial ports looking for NMEA sentences. When NMEA data is found, it will provide a location on the map.


 



Three separate screenshots were combined in order to show all the steps simultaneously

 

Note: An Arduino (or any other microcontroller) is not strictly required for this to work. A GPS module (such as the Adafruit logger shield) that can be programmed to transmit the desired sentences at 4800 baud can be connected directly to an HC-12. Data can then be sent to Google Earth using a separate HC-12 that is connected to a computer's serial port via a logic-level-to-RS232 converter.

Conclusion

This two-article series demonstrates that the HC-12 is a versatile and easy-to-use RF transceiver module. It is similar to the nRF24L01, but it offers the important advantage of longer range. The straightforward UART interface facilitates integration into a wide variety of systems—microcontrollers and PCs can directly communicate with the HC-12.

As this article has shown, the HC-12 is a simple solution for logging GPS data and for real-time GPS tracking.

 

Featured image courtesy of SpaceX.



 


	
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52 Comments

Darius Petrulis November 21, 2016

Nice project, to use this GPS tracker for almost unlimited distance you need to replace HC-12 transceiver to GSM module e.g.SIM800, just need some code changes 😉

Like. Reply
- Mark Hughes November 25, 2016
  
  Hello Darius, That is true -- however, the purpose of parts one and two of this series were to use a serial transceiver for communication. Also, using a cellular device would incur a fee -- these are free after purchase. Thanks -- and consider registering an account with us and joining the community. Mark
  Like. Reply
R
ronsoy2 November 25, 2016

Very cute project! Thing to keep in mind is that it REQUIRES a proper number of satellites be received during the measurement period. The horrible accuracy shown above possibly is because not enough satellites were being picked up at the time. This is seriously affected by GPS antenna module orientation and overhead obstruction.

Like. Reply
- Mark Hughes November 25, 2016
  
  That's entirely possible. I live in a relatively steep canyon that limits my view of the sky, although I can usually get at least four satellites. I also suspect multipath signal propagation errors -- signals bouncing off of things on the canyon walls or the houses on the ridgeline, adding that much more length to the signal path.
  Like. Reply
K
Kilili November 25, 2016

The 4 links below are bogus:
HC-12 Getting Started
HC-12 Sending Remote Commands
Realtime TrackGPS
GPS Transmit Location

Like. Reply
- Mark Hughes November 25, 2016
  
  Hi @Kilili, I just tried the links you mentioned as was able to download the files. Were you signed in when you tried it? They're also available in the first part of the article
  Like. Reply
- - Mark Hughes November 25, 2016
    
    @ Kilili, I just fouled the new link! Ha! Sorry about that. Understanding and Implementing the HC-12 transmitter If that doesn't work, you can also find it big and bold at the top of the page. Mark
    Like. Reply
T
tania123 June 23, 2017

Hi, can I use a Bluetooth Hc-06 instead?
thank you

Like. Reply
- Mark Hughes June 23, 2017
  
  The HC-06 has enough similar features that you should be able to get it to work -- but the range will be a fraction of what the HC-12 is capable of. (The range of the HC-12 is 1000 m, the HC-06 will be between 1 m - 10m)
  Like. Reply
G
giachou_s September 03, 2017

great article plz some question.can i use one hc 12 rxd with multiple rxds?
to make it work i will only need hc12-battery-gps module?
do i need to conect external ant to get 1km range?
thx!

Like. Reply
- Mark Hughes September 03, 2017
  
  Hi @giachou_s, Yes, you can use a single transmitter with multiple receivers without any issue. And yes, for the maximum range you need an external antenna (the higher off the ground the better). Mark
  Like. Reply
- - G
    giachou_s September 04, 2017
    
    sorry Mark i belive i AM total wrong about my question.i want to make multiple transmitters to go in one receiver.can the one handle about 7 trasmitters? thx again for your time
    Like. Reply
  - - Mark Hughes September 04, 2017
      
      Hi @giachou_s, Yes, that will work too. However, you need to ensure that only one is transmitting at a time. Depending on what you're doing you might be able to accomplish this by sequentially transmitting according to a time-table -- one transmitter every second. If (Mod[seconds, 7]==n) then transmit, where n=(1,2,3,4,5,6,7), one for each transmitter. Good luck. Mark
      Like.
Amit Yungerman October 07, 2017

I would like to ask what adaptations I would have to do in order to use other common cheap generic modules of GPS ?
Thanks in advance.

Like. Reply
- Mark Hughes October 07, 2017
  
  Which module did you have in mind?
  Like. Reply
- - Amit Yungerman October 20, 2017
    
    Sorry about the delay! not sure , prefer something that will be compatible to your tutorial but a generic one from the ebay which will be cheaper!
    Like. Reply
  - - Amit Yungerman October 20, 2017
      
      for ex. this one https://www.ebay.com/itm/GPS-NEO-6M-GY-GPS6MV2-Module-Aircraft-Flight-Control-For-Arduino-MWC-IMU-APM2-/162218163069?var=&hash=item25c4f4bb7d:m:m2JSR1XrzmMSpQFTUxD1nrQ
      Like.
    - Mark Hughes October 20, 2017
      
      @Amit Yungerman, My best guess is that you can get that working with the sketch. I mean for $6, you almost have to try it.
      Like.
    - Amit Yungerman October 25, 2017
      
      Thank's man!
      Like.
S
SpearlikeTag2 October 16, 2017

Hello, I tried to use Example Program 3 with an Arduino 101, but it seems to not be transmitting and whenever I type a command, such as “AT+RX”, nothing appears on the serial monitor. However, from example program 2 on your previous article “Understanding and Implementing the HC-12,” I was able to transmit successfully with 2 HC-12 transceivers and was able to send commands. For example, when I sent “AT+RX” using Example Program 2, I got this back on the serial monitor:
AT+RX
OK+B9600
OK+RC001
OK+RP:+20dBm
OK+FU3
Remote Command Executed

Like. Reply
- Mark Hughes October 16, 2017
  
  Hi @SpearlikeTag2, Let me preface my answer by saying I've never seen or used a 101, and up until your post, I wasn't aware that they existed -- so I might not be able to satisfactorily answer your question. Example 3 attempts to integrate the GPS into the sketch by creating a second software based UART port for the GPS. Since that sketch was written, the 101 was released and it appears to handle UART communication differently. Perhaps it requires you to create separate classes for the two ports, I'm not entirely certain. I would recommend the following steps. 1) Use an oscilloscope to ensure that the GPS is transmitting data to the Arduino 101 and it is at the proper voltage level. If the voltage levels of the serial data appear too low, you can try a strong pull up resistor. 2) Read the documentation for the 101. It's possible that not all of the pins are compatible (e.g. you cannot receive on pin 4, but you can on pin 0). It's also possible that there are different programming techniques for the 101, and the libraries might have changed -- commands I used for the Uno with an older compiler might not work on the 101 and the new compiler. 3) Forget about the GPS and the HC12 for a moment and focus on establishing two UART channels -- find an Arduino 101 forum and sketch that implements two additional UARTs (Your computer is one, the HC12 is two, and the GPS is three). You can use your computer for the primary, program your second 101 to output a sting of text (that's two), and use the GPS as three. If you can get strings two and three into your serial monitor (one), then you at least know it is possible with your hardware. Sorry, I can't be of more help. Consider starting a forum topic and asking our community -- I'm sure we have 101 users out there. Good luck, Mark
  Like. Reply
Dzikra Amri November 26, 2017

HOW trying to determine the distance between two GPS units

Like. Reply
F
FauxFenix December 17, 2017

Okay, I am completely new to arduino and these things but would I be wrong to think that there would be a way to use something from a gps unit (the kind that gives you directions, not the gps on a smartphone) to get more range for this project?

Like. Reply
- Mark Hughes December 17, 2017
  
  @FauxFenix, The range of this project is limited by the HC12, not the GPS unit used.. Mark
  Like. Reply
A
Agir December 30, 2017

Hi,
Thanks for the information. This is a great project. I fly hang gliders and often cover distances of over 100kms from launch. The areas I fly often have no or weak GSM signals so communication between the car and hang glider is best done through a two way radio. I carry a UHF radio that can easily transmit over 100kms as we have a clear line of sight in the flat-lands where I fly. I would like to link my UHF radio to a GPS tracker to send a radio signal back to a base station that could interpret the signal and convert it to a position on Google maps for my wife to find me. Is this possible? And if so, do you know how to make such a device/s?

Like. Reply
- Mark Hughes December 31, 2017
  
  There are several ways to accomplish that goal -- one that comes quickly to mind is APRS. You can purchase HT transmitters with GPS built in that will transmit out at pre-defined intervals or when interrogated. Or purchase an add-on kit that attaches to your current radio. The GPS and TNC goes flying with you (you'll need an Amateur Radio License but they're pretty easy to come by). On your wife's end of things, you'll need a Terminal Node Controller hooked up to some receiver tuned to the same frequency. There are hardware options out there to connect the TNC to your phone / computer / raspberry pi, whatever you want. Google "APRS Tracker" or focus your search terms on "balloon tracker" for more information. Good luck, Mark
  Like. Reply
P
paulkotis February 28, 2018

Hi Mark, Thanks for the details.

When the GPS is transmitted can I receive it on my cell phone/tablet or it has to be a HC 12 at the other end?

Like. Reply
- Mark Hughes February 28, 2018
  
  Hi @paulkotis, HC12s can only communicate with other HC12s. It should be possible to use an IC such as Texas Instruments CC2640 (Bluetooth LE) to act as an intermediary between your HC12 and the cell phone, but at that point, it might just make sense to hook the GPS up to the CC2640 and do away with the HC12 altogether. Hope this helps. Mark
  Like. Reply
Riaz Sulaimi April 20, 2018

Hi bro!, This is an awesome project. Are there any schematics/fritzing diagram for the hooking up of HC12 with the gps logger? Thanks!

Like. Reply
- Mark Hughes April 21, 2018
  
  Hi @Riaz Sulaimi, I'm glad that you enjoyed the project. The two pictures with the orange-colored rounded-rectangles and numbers are the hookup diagram/schematic. There is no fritzing diagram perse, but if you buy the shield, it'll plug directly into the arduino and solve half of your problems. It's only an additional four or five wires to add the HC12, so it shouldn't be too difficult a task. If you need help, please post in our forums and ping me and I'll try to jump in to help out.
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- - Riaz Sulaimi May 13, 2018
    
    Thanks much bro! will give it a try! :)
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  - Riaz Sulaimi May 13, 2018
    
    Sorry for noob qustions but if i use adafruit gps shield do i still need the capacitors because in the picture i saw that you have added some capacitors to the setup for the gps shield. Actually its the capacitor connection that i am not too sure about. Thanks!
    Like. Reply
  - - Mark Hughes May 13, 2018
      
      Riaz, The only way to tell for sure is by using an oscilloscope to track the voltage while the device is operating under a variety of situations. Sometimes you can get away without them, and sometimes not using one will instantly and permanently damage your component. It's not going to hurt anything, and it can certainly help mitigate any transient voltage drops during transmission of the HC12. In general, any recommendations that come from a datasheet should be followed strictly. Just to be clear -- the reservoir cap is for the HC12, not the GPS. Using the GPS shield or the standalone GPS shouldn't make a difference. Best, Mark
      Like.
  - Riaz Sulaimi May 13, 2018
    
    Hi Mark, I just re-read everything and saw your Part1 and read that as well and I think i have figured it out and will give it a try. Sorry for the trouble and many posts. Thanks!
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sjp187 May 18, 2018

Hi Mark,
This is a really neat little project, and thank you for still engaging with people’s questions on it (including mine, I hope!). I’ve followed your initial guide on connecting two HC12s to send messages back and forwards, and completed that no issues.

I’m now trying this set up, where one unit has the Arduino, GPS shield, and HC12, and the receiver is just an Arduino and HC12. I’ve checked the GPS shield in standalone mode and it works (as in I can see full NMEA sequences coming through on Port Monitor), but as soon as I upload your code to make it transmit via the HC12, it runs maybe a line and a half of NMEA code (visible on the Port Monitor) before stopping, and nothing at all is received by the other HC12.

Have you any suggestions as to what I may be able to try to debug it? Thanks very much! 😊

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- Mark Hughes May 19, 2018
  
  Hi @sjp187, Thanks for joining the site. You sure you don't want to start with an easier question? That's a tough one! First -- this is probably going to require a bit of back-and-forth, and I'd love to get some other site expert's opinions as well. Could you start a forum post in https://forum.allaboutcircuits.com/ and ping me (use the @ followed by username). I wonder if you're experiencing a power-related problem? Perhaps the reservoir capacitor wired to the HC12 is not of sufficient capacity? And just to confirm -- you saw the warnings to not power the Arduino over USB alone -- you need an external power supply. Any chance you have an oscilloscope, or at least a multimeter that you can put on the HC12's power pins to see if the voltage is dropping? It's possible that your computer is seeing a power surge over the USB port and shutting down/resetting the port. Hope this helps -- see you in the forums! Mark
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D Rieger May 19, 2018

New to this site. What would be needed to transmit just the speed and be able to read it without a computer hooked up. I sail remote control sail boats and would like to see the speed changes when I sheet in the sails
Thanks
Doug

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- Mark Hughes May 19, 2018
  
  Hi @D Rieger, Welcome to the site! Yes -- that is absolutely possible, and not too difficult to do. However, we'll need to discuss it in a forum-post -- as it will involve code and a few back and forth exchanges. See you in the forums http://forum.allaboutcircuits.com
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knete May 25, 2018

Hi Mark,
thank you very much for the detailed project description.
I was just wondering if it is possible to use the HC-12 to set up a simple mesh network to forward messages and extend the range. Ok, I know it is possible, but the question is how. 😉
Do you have any references or sites where I can get started?
My idea is to set up multiple nodes on an area to track a device with HC-12+Arduino+GPS from another mobile device with the same configuration.
Thanks for your effort in advance!
Marc

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- Mark Hughes May 25, 2018
  
  Hi Marc @knete, This really can become something of a complicated issue. I'd recommend posting this comment in our forums to see what others have to say. When you create your post -- can you explain a bit more about your project? Are you just tracking one target? Is the receiver always centrally located? What is the overall area of coverage you need? You might be able to create a simple repeater network that blends two HC12s (on different channels) with a power supply (No Arduino -- Rx of one to Tx of another). Create a forum post and then ping me with the @ symbol and I'll see if I can't help you get started. Best, Mark
  Like. Reply
Riaz Sulaimi July 04, 2018

Hi Mark,

This has been one awesome project that my primary school students are trying out. So far they have managed to get everything to work except for the real time tracking with Google Earth Pro. If they were to collect the NMEA data from the serial monitor and save it to a kml file, the movement of the tracker shows up nicely. However trying out using realtime via google earth, the usb and com port gets detected but no data is showing up.

Any ideas why such an error occurs? They have been doing some research and were wondering if it has anything to do with the carriage return and new line at end of each nmea line?

Thanks!

Riaz

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Craig Peterson August 20, 2018

Is it also able to do the reverse and transmit a GPS signal to an Android or Iphone using Google Maps or Pokemon Go any other maps to trick the device into thinking it is someplace else? 😊

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- Mark Hughes August 20, 2018
  
  Hi Craig, Sorry -- no. You'd have to integrate a bluetooth transceiver for that to work.
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volthauslab September 22, 2018

The Links in the above article are links to zipped files so if you them right click the link and then select “save as” to download the files.
The HC-12 Getting Started
HC-12 Sending Remote Commands
Realtime TrackGPS
GPS Transmit Location

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sgoemans October 27, 2018

I went through all your examples and I’ve learned a lot. Thank you.
Your last sketch (Example Program 4) seems to have a few bugs, though:
1) #include &let;SoftwareSerial.h>
2) GPSbyteIn and GPSBuffer3 not defined
3) The comment “Connect GPS “RXD” to Arduino Digital Pin 8” must change to “TXD”.
4) The download link “RealtimeTrackGPS” downloads example 3 instead of 4

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GiorgosK December 15, 2018

Hi Mark. Sorry for my english.

First of all, you are very kind answering all our questions.

I see that it is possible to pair the HC-12 with an android (enabled gps) smartphone via a bluetooth module (no need to use arduino or gps module,right?).
Having two smartphones, what kind of software do I need to make one of them show the location of the other in Google Maps or a kind of app that uses Google Satellite?

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- Mark Hughes December 15, 2018
  
  Hello @GiorgosK, I'm afraid I have never tried that. But a search of the GooglePlay store showed an app called Bluetooth GPS Output (https://play.google.com/store/apps/details?id=com.meowsbox.btgps&hl=en). I have never used the software myself. You might try posting your question in our forums (https://forum.allaboutcircuits.com/) to reach a larger number of people. Good luck! Mark
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- - G
    GiorgosK December 15, 2018
    
    Thanks Mark for your quick response. I post it in the forum. https://forum.allaboutcircuits.com/threads/hc-12-hc-06-android.154992/ I have already installed this app, but since I wait for my HC-12 order, I cannot do anything yet.
    Like. Reply
Seth Petersen February 27, 2019

Hello I was wondering if you think the data collected from the GPS transmission could be interpreted by an Arduino to command motors to drive a vehicle to the position that the GPS module indicated.

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- Mark Hughes February 27, 2019
  
  It is certainly possible, but personally I would choose a more powerful MCU. You might find as you experiment that you need to create some obstacle detection and avoidance, or implement the Haversine or Vincenty formula, and an 8 bit microcontroller will be too hard to work with. Use at least a 16 bit or 32 bit.....maybe check out what the folks over at ArduPilot are doing. It isn't impossible. But it is easier with more powerful tools.
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MichaelKlos April 24, 2020

😂

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Chrisfol82 November 21, 2020

Would it be possible to make the project work to show the realtime GPS data on google earth by utilizing just the GPS module, Battery, and HC12 on one end and the arduino/HC12 on the other end connected to my computer? Ive gotten this setup working and transmitting the GPS data using some fo the code examples in your article, but im not sure how to get the data to work with google Earth. The code you used in your example was using an arduino on the GPS end, i wanted to try to make this work without the arduino on the GPS end. Would this work if i had the right code?

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