GPS + BDS BeiDou Dual Module Flight Control Wiki - DFRobot

Introduction

This is a small-size positioning and navigation module based on the AT6558 (a real sixes in one multi-mode satellite navigation and positioning chip). It can provide real-time location information, and support a variety of satellite navigation systems, including 32 tracking channels. Besides, the module can receive GNSS signal from 6 satellite navigation systems simultaneously, which include China BDS (Beidou navigation satellite system), the American GPS, the Russian GLONASS, European GALILEO, Japan QZSS and SBAS satellite augmentation system (WAAS, EGNOS, GAGAN MSAS), and realize the joint positioning, navigation and timing.

In serial output mode, the module is compatible with various mainboards equipped with serial output: Arduino, Raspberry Pi, STM32 and so on. The positioning accuracy error is measured at about 3m, basically the same as smartphones. The module’s power consumption is as low as 0.1W, and it can work continuously for a long time with a small power supply.

The small size of the module allows it to be embedded in various types of drones and smart cars. Furthermore, this module can be very suitable for vehicle navigation, handheld positioning and wearable devices or be used as a replacement of Ublox MAX series module.

Specification

• Operating Voltage: 3.3-5V
• SMA and IPEX Antenna Ports
• Onboard E2PROM for storing configuration settings
• Onboard XH414 rechargeable battery, speed up hot-start and search
• Support A-GNSS
• Cold- start Acquisition Sensitivity: -148dBm
• Tracking Sensitivity: -162dBm
• Positioning Accuracy: 2.5m(CEP50, open field)
• Time to First Fix: 32 seconds (or few minutes, depends on the environment)
• Low Power: <25mA (work continuously)
• Built-in antenna detection and antenna short circuit protection function
• Dimension: 13.1 x 15.7mm/0.52 x 0.62”

Board Overview

Module Introduction

• Outline Dimension (Unit: mm)

• PCB layout (Unit: mm)

• PinOut

• Pin Definition

• Electrical Parameters

1. Limit Parameter

2. Operating Conditions

• Technical Specification

Data Analysis

It is recommended to test this module in an outdoor open place since if the antenna is placed on a balcony, its signal may be influenced by the buildings around. The positioning can be done within one minute in open spaces. When the onboard LED keeps flashing at a regular frequency, the positioning is completed. The default baudrate is 9600. Now let us check the data in the serial monitor.

$GNGGA,084852.000,2236.9453,N,11408.4790,E,1,05,3.1,89.7,M,0.0,M,,*48

$GNGLL,2236.9453,N,11408.4790,E,084852.000,A,A*4C

$GPGSA,A,3,10,18,31,,,,,,,,,,6.3,3.1,5.4*3E

$BDGSA,A,3,06,07,,,,,,,,,,,6.3,3.1,5.4*24

$GPGSV,3,1,09,10,78,325,24,12,36,064,,14,26,307,,18,67,146,27*71

$GPGSV,3,2,09,21,15,188,,24,13,043,,25,55,119,,31,36,247,30*7F

$GPGSV,3,3,09,32,42,334,*43

$BDGSV,1,1,02,06,68,055,27,07,82,211,31*6A

$GNRMC,084852.000,A,2236.9453,N,11408.4790,E,0.53,292.44,1412 16,,,A7 5 $GNVTG,292.44,T,,M,0.53,N,0.98,K,A2D

$GNZDA,084852.000,14,12,2016,00,00*48

$GPTXT,01,01,01,ANTENNA OK*35

There are three data types in the data: GN, GP and BD, which respectively represent the dual-mode mode, GPS mode, and Beidou mode.

NMEA0318 protocol frame format content can refer to the following forms:

(1) $GPGGA (GPS location information)

(2) $GPGLL (Geographic Position Information)

(3) $GPGSA (Current Satellites Information)

(4) $GPGSV (Satellites in View)

(5) $GPRMC (Minimum GNSS Data)

(6) $GPVTG (Ground Speed Information)

(7) Antenna Status Output

$GPTXT，01,01,01, ANTENNA OK*35

"Ok" means that the antenna has been detected, and "open" represents the antenna is disconnected.

(8) UTC time and Current time in Beijing

$GNGGA,084852.000,2236.9453,N,11408.4790,E,1,05,3.1,89.7,M,0.0,M,,*48

The numbers in bold represent UTC time. Its format is hhmmss.sss. The three digits after the decimal point should be omitted so the numbers above means that it is 08:48:52.

UTC + Time Zone Difference = Local Time

The time of eastern zone is positive, the western zone is negative. The time in Beijing follows the time offset of UTC+08:00 so the current time in Beijing is 16:48:52.

(9) Format of latitudes and longitudes

$GNRMC,084852.000,A,2236.9453,N,11408.4790,E,0.53,292.44,141216,,,A*7 5

Data format: ddd°mm.mmm’ Convert to the format of Google or Baidu Map. Latitude: ddmm.mmmm, Northern Latitude 2236.9453，22+(36.9453/60)= 22.615755 Longitude: dddmm.mmmm, East Longitude 11408.4790，114+(08.4790/60)=114.141317

(10) Description of hot start, warm start and cold start

The Cold Start refers to the process of starting GPS in an unfamiliar environment until it connects with the surrounding satellites and calculates coordinates.

The following three situations are all cold start:

1. Use for the first time;
   

2. Ephemeris information lost due to batterry depletion;
   

3. Move the receiver more than 1000km in power off state. That is to say, the cold start is a mandatory start-up through hardware. When the GPS has cleared the internal positioning information since the last operation, and the GPS receiver has lost satellites parameters, or the navigator cannot work properly because existing parameters because the existing parameters are too different from the actual received satellite parameters, it is necessary for GPS to obtain the new coordinate data provided by the satellite. A vehicle startting a navigation from a basement is cold start. This is also the reason why it takes a long time to search for satellites from the basement.
   

Warm start refers to the start-up more than 2 hours from the last positioning time. The positioning time is between cold start and hot start. If you have used GPS positioning one day ago, the first startup of next day belongs to warm start, and the last position information will be displayed after startup. The latitude, longitude and altitude of the last operation are known, but since the shutdown time is too long, the ephemeris has changed and the previous cannot accept it. Several satellittes in the parameters have lost contact with the GPS receiver and have to continue searching for additional position information. Therefore, searching time for warm start is longer than that of hot start and shorter than cold start.

When starting GPS at the place where it was shut down last time, and the time from last positioning time is less than 2 hours, it is hot start. Some preparation work such as saving and closing can be done by software.

Tutorial

Requirements

• Hardware
  • Arduino UNO
  • GPS + BDS BeiDou Dual Module x1
  • Wires

• Software
  • Arduino IDE

Connection Diagram

Sample Code 1 (Read GPS Data)

#include <SoftwareSerial.h> 
SoftwareSerial GpsSerial(11, 12); //RX,TX

void setup()
{   
  Serial.begin(115200);  //Debug Serial 
  GpsSerial.begin(9600);  //Gps Serial   
} 

void loop()
{  while (GpsSerial.available() > 0)
  { 
    byte gpsData = GpsSerial.read(); 
   Serial.write(gpsData); 
  }
}

Expected Results 1

Sample Code 2 ($GNRMC GPS Data Analysis)

#include <SoftwareSerial.h>
SoftwareSerial GpsSerial(12, 11);  //RX,TX

struct
{
  char GPS_DATA[80];
  bool GetData_Flag;      //Get GPS data flag bit
  bool ParseData_Flag;    //Parse completed flag bit 
  char UTCTime[11];       //UTC time
  char latitude[11];      //Latitude
  char N_S[2];            //N/S
  char longitude[12];     //Longitude
  char E_W[2];            //E/W
  bool Usefull_Flag;      //If the position information is valid flag bit 
} Save_Data;

const unsigned int gpsRxBufferLength = 600;
char gpsRxBuffer[gpsRxBufferLength];
unsigned int gpsRxLength = 0;

void setup()
{
  Serial.begin(115200);   //Debug Serial
  GpsSerial.begin(9600);  //Gps Serial

  Serial.println("DFRobot Gps");
  Serial.println("Wating...");

  Save_Data.GetData_Flag = false;
  Save_Data.ParseData_Flag = false;
  Save_Data.Usefull_Flag = false;
}

void loop()
{
  Read_Gps();         //Get GPS data 
  parse_GpsDATA();    //Analyze GPS data 
  print_GpsDATA();    //Output analyzed data 
}

void Error_Flag(int num)
{
  Serial.print("ERROR");
  Serial.println(num);
  while (1)
  {
    digitalWrite(13, HIGH);
    delay(500);
    digitalWrite(13, LOW);
    delay(500);
  }
}

void print_GpsDATA()
{
  if (Save_Data.ParseData_Flag)
  {
    Save_Data.ParseData_Flag = false;

    Serial.print("Save_Data.UTCTime = ");
    Serial.println(Save_Data.UTCTime);

    if(Save_Data.Usefull_Flag)
    {
      Save_Data.Usefull_Flag = false;
      Serial.print("Save_Data.latitude = ");
      Serial.println(Save_Data.latitude);
      Serial.print("Save_Data.N_S = ");
      Serial.println(Save_Data.N_S);
      Serial.print("Save_Data.longitude = ");
      Serial.println(Save_Data.longitude);
      Serial.print("Save_Data.E_W = ");
      Serial.println(Save_Data.E_W);
    }
    else
    {
      Serial.println("GPS DATA is not usefull!");
    }    
  }
}

void parse_GpsDATA()
{
  char *subString;
  char *subStringNext;
  if (Save_Data.GetData_Flag)
  {
    Save_Data.GetData_Flag = false;
    Serial.println("************************");
    Serial.println(Save_Data.GPS_DATA);

    for (int i = 0 ; i <= 6 ; i++)
    {
      if (i == 0)
      {
        if ((subString = strstr(Save_Data.GPS_DATA, ",")) == NULL)
          Error_Flag(1);    //Analysis error 
      }
      else
      {
        subString++;
        if ((subStringNext = strstr(subString, ",")) != NULL)
        {
          char usefullBuffer[2]; 
          switch(i)
          {
            case 1:memcpy(Save_Data.UTCTime, subString, subStringNext - subString);break;    //Get UTC time 
            case 2:memcpy(usefullBuffer, subString, subStringNext - subString);break;        //Get position status 
            case 3:memcpy(Save_Data.latitude, subString, subStringNext - subString);break;   //Get latitude information 
            case 4:memcpy(Save_Data.N_S, subString, subStringNext - subString);break;        //Get N/S
            case 5:memcpy(Save_Data.longitude, subString, subStringNext - subString);break;  //Get longitude information 
            case 6:memcpy(Save_Data.E_W, subString, subStringNext - subString);break;        //Get E/W

            default:break;
          }
          subString = subStringNext;
          Save_Data.ParseData_Flag = true;
          if(usefullBuffer[0] == 'A')
            Save_Data.Usefull_Flag = true;
          else if(usefullBuffer[0] == 'V')
            Save_Data.Usefull_Flag = false;
        }
        else
        {
          Error_Flag(2);    //Analysis error
        }
      }
    }
  }
}

void Read_Gps() 
{
  while (GpsSerial.available())
  {
    gpsRxBuffer[gpsRxLength++] = GpsSerial.read();
    if (gpsRxLength == gpsRxBufferLength)RST_GpsRxBuffer();
  }

  char* GPS_DATAHead;
  char* GPS_DATATail;
  if ((GPS_DATAHead = strstr(gpsRxBuffer, "$GPRMC,")) != NULL || (GPS_DATAHead = strstr(gpsRxBuffer, "$GNRMC,")) != NULL )
  {
    if (((GPS_DATATail = strstr(GPS_DATAHead, "\r\n")) != NULL) && (GPS_DATATail > GPS_DATAHead))
    {
      memcpy(Save_Data.GPS_DATA, GPS_DATAHead, GPS_DATATail - GPS_DATAHead);
      Save_Data.GetData_Flag = true;

      RST_GpsRxBuffer();
    }
  }
}

void RST_GpsRxBuffer(void)
{
  memset(gpsRxBuffer, 0, gpsRxBufferLength);      //Clear
  gpsRxLength = 0;

Result 2

FAQ

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