GPS Modules - johnosbb/Automation GitHub Wiki
GT-U7-GPS Module
This is a compact GPS module made by open-smart and utilises the GT-U7 GPS receiver. The module also includes a USB serial interface which can be accessed via a micro USB connector or directly via its 0.1” pitch serial TTL header (supplied header pins requires soldering). Out of the box the module will automatically output GPS data in the standard NMEA format making it compatible with many types of hardware and software with no configuration required. The module is also supplied with a detachable antenna which connects to the module via a U.FL pigtail cable allowing the antenna to be located in the optimal position.
Specification
- Product code: HCMODU0172
- Operating frequency: L1 (1575.42 +/- 10MHz)
- Operating voltage: 3.3 - 5.2V
- Operating current: normal mode is 50mA, power-saving mode is 30mA
- Communication interface: TTL serial port, micro USB interface (can be connected to a computer to debug)
- Serial port baud rate: 9600bps
- Communication format: 8N1
- Interface logic voltage: 3.3V or 5V
- External antenna interface: IPX.
- Module dimensions: 27.5 x 26.5 x 4mm
- Antenna dimensions: 15.3 x 15.3 x 6.8mm
Note: It can take up to 15 minutes for a factory fresh GPS unit to obtain a cold start fix.
To debug issues you can use the following code:
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); //(RX, TX) check correct pin assignments.
void setup() {
mySerial.begin(9600);
Serial.begin(9600);
Serial.println("GPS start");
}
void loop() {
while (mySerial.available()) {
Serial.write(mySerial.read());
}
}
Example Code
#include <SoftwareSerial.h>
SoftwareSerial GPSSerial(10, 11); //(RX, TX) check correct pin assignments.
//--------------------------------------
//NOTE: you should upload the code first and then connect to GPS module
//Wiring guide
//GT-U7 GPS ---- Arduino UNO R3 / OPEN-SMART UNO
// VCC ---- 5V
// GND ---- GND
// RXD ---- NOT CONNECT
// TXD ---- RX (Pin 10) for Soft Serial
// PPS ---- NOT CONNECT
//--------------------------------------
#define GPRMC_TERM "$GPRMC," //Defines the instruction to be parsed, and it contains positioning and time information
char nmeaSentence[68];
String latitude;
String longitude;
String lndSpeed;
String gpsTime; //time of prime meridian
String gmtTime; //time in London
void setup()
{
Serial.begin(9600);
GPSSerial.begin(9600);
delay(10);
}
void loop() //
{
// For one second we parse GPS data and report some key values
for (unsigned long start = millis(); millis() - start < 1000;) //Keep searching GPS information in one second
{
while (GPSSerial.available()) //The serial port gets the data and starts parsing
{
char c = GPSSerial.read();
switch(c)
{
case '$': //$ is the beginning of a frame of data
GPSSerial.readBytesUntil('*', nmeaSentence, 67);
//Serial.println(nmeaSentence);
latitude = parseGprmcLat(nmeaSentence);
longitude = parseGprmcLon(nmeaSentence);
lndSpeed = parseGprmcSpeed(nmeaSentence);
gpsTime = parseGprmcTime(nmeaSentence);
if(latitude > "") //If it is not null, print out the value
{
Serial.println("------------------------------------");
Serial.println("latitude: " + latitude);
}
if(longitude > "") //If it is not null, print out the value
{
Serial.println("longitude: " + longitude);
}
if(lndSpeed > "") //If it is not null, print out the value
{
Serial.println("Speed (knots): " + lndSpeed);
}
if(gpsTime > "") //If it is not null, print out the value
{
Serial.println("gpsTime: " + gpsTime);
gmtTime = getGMTTime(gpsTime); //Calculate GMT time
Serial.println("GMT Time: " + gmtTime);
}
}
}
}
}
String getGMTTime(String s)
{
int hour = s.substring(0, 2).toInt(); // Extract hours
int minute = s.substring(2, 4).toInt(); // Extract minutes
int second = s.substring(4, 6).toInt(); // Extract seconds
// Format hours, minutes, and seconds with leading zeros if needed
String formattedTime = (hour < 10 ? "0" : "") + String(hour) + ":" +
(minute < 10 ? "0" : "") + String(minute) + ":" +
(second < 10 ? "0" : "") + String(second);
return formattedTime;
}
//Parse GPRMC NMEA sentence data from String
//String must be GPRMC or no data will be parsed
//Return Latitude
String parseGprmcLat(String s)
{
int pLoc = 0; //paramater location pointer
int lEndLoc = 0; //lat parameter end location
int dEndLoc = 0; //direction parameter end location
String lat;
/*make sure that we are parsing the GPRMC string.
Found that setting s.substring(0,5) == "GPRMC" caused a FALSE.
There seemed to be a 0x0D and 0x00 character at the end. */
if(s.substring(0,4) == "GPRM")
{
//Serial.println(s);
for(int i = 0; i < 5; i++)
{
if(i < 3)
{
pLoc = s.indexOf(',', pLoc+1);
/*Serial.print("i < 3, pLoc: ");
Serial.print(pLoc);
Serial.print(", ");
Serial.println(i);*/
}
if(i == 3)
{
lEndLoc = s.indexOf(',', pLoc+1);
lat = s.substring(pLoc+1, lEndLoc);
/*Serial.print("i = 3, pLoc: ");
Serial.println(pLoc);
Serial.print("lEndLoc: ");
Serial.println(lEndLoc);*/
}
else
{
dEndLoc = s.indexOf(',', lEndLoc+1);
lat = lat + " " + s.substring(lEndLoc+1, dEndLoc);
/*Serial.print("i = 4, lEndLoc: ");
Serial.println(lEndLoc);
Serial.print("dEndLoc: ");
Serial.println(dEndLoc);*/
}
}
return lat;
}
//}
//}
}
//Parse GPRMC NMEA sentence data from String
//String must be GPRMC or no data will be parsed
//Return Longitude
String parseGprmcLon(String s)
{
int pLoc = 0; //paramater location pointer
int lEndLoc = 0; //lat parameter end location
int dEndLoc = 0; //direction parameter end location
String lon;
/*make sure that we are parsing the GPRMC string.
Found that setting s.substring(0,5) == "GPRMC" caused a FALSE.
There seemed to be a 0x0D and 0x00 character at the end. */
if(s.substring(0,4) == "GPRM")
{
//Serial.println(s);
for(int i = 0; i < 7; i++)
{
if(i < 5)
{
pLoc = s.indexOf(',', pLoc+1);
/*Serial.print("i < 3, pLoc: ");
Serial.print(pLoc);
Serial.print(", ");
Serial.println(i);*/
}
if(i == 5)
{
lEndLoc = s.indexOf(',', pLoc+1);
lon = s.substring(pLoc+1, lEndLoc);
/*Serial.print("i = 3, pLoc: ");
Serial.println(pLoc);
Serial.print("lEndLoc: ");
Serial.println(lEndLoc);*/
}
else
{
dEndLoc = s.indexOf(',', lEndLoc+1);
lon = lon + " " + s.substring(lEndLoc+1, dEndLoc);
/*Serial.print("i = 4, lEndLoc: ");
Serial.println(lEndLoc);
Serial.print("dEndLoc: ");
Serial.println(dEndLoc);*/
}
}
return lon;
}
}
//Parse GPRMC NMEA sentence data from String
//String must be GPRMC or no data will be parsed
//Return Longitude
String parseGprmcSpeed(String s)
{
int pLoc = 0; //paramater location pointer
int lEndLoc = 0; //lat parameter end location
int dEndLoc = 0; //direction parameter end location
String lndSpeed;
/*make sure that we are parsing the GPRMC string.
Found that setting s.substring(0,5) == "GPRMC" caused a FALSE.
There seemed to be a 0x0D and 0x00 character at the end. */
if(s.substring(0,4) == "GPRM")
{
//Serial.println(s);
for(int i = 0; i < 8; i++)
{
if(i < 7)
{
pLoc = s.indexOf(',', pLoc+1);
/*Serial.print("i < 8, pLoc: ");
Serial.print(pLoc);
Serial.print(", ");
Serial.println(i);*/
}
else
{
lEndLoc = s.indexOf(',', pLoc+1);
lndSpeed = s.substring(pLoc+1, lEndLoc);
/*Serial.print("i = 8, pLoc: ");
Serial.println(pLoc);
Serial.print("lEndLoc: ");
Serial.println(lEndLoc);*/
}
}
return lndSpeed;
}
}
//Parse GPRMC NMEA sentence data from String
//String must be GPRMC or no data will be parsed
//Return Longitude
String parseGprmcTime(String s)
{
int pLoc = 0; //paramater location pointer
int lEndLoc = 0; //lat parameter end location
int dEndLoc = 0; //direction parameter end location
String gpsTime;
/*make sure that we are parsing the GPRMC string.
Found that setting s.substring(0,5) == "GPRMC" caused a FALSE.
There seemed to be a 0x0D and 0x00 character at the end. */
if(s.substring(0,4) == "GPRM")
{
//Serial.println(s);
for(int i = 0; i < 2; i++)
{
if(i < 1)
{
pLoc = s.indexOf(',', pLoc+1);
/*Serial.print("i < 8, pLoc: ");
Serial.print(pLoc);
Serial.print(", ");
Serial.println(i);*/
}
else
{
lEndLoc = s.indexOf(',', pLoc+1);
gpsTime = s.substring(pLoc+1, lEndLoc);
/*Serial.print("i = 8, pLoc: ");
Serial.println(pLoc);
Serial.print("lEndLoc: ");
Serial.println(lEndLoc);*/
}
}
return gpsTime;
}
}
// Turn char[] array into String object
String charToString(char *c)
{
String val = "";
for(int i = 0; i <= sizeof(c); i++)
{
val = val + c[i];
}
return val;
}