SimCom provides us with a system of AT Command commands to control the GPS. The important thing is the ability to apply commands to each application we want.

      Here are some AT Command commands you can refer to:

        1.1 Overview:





điều khiển nguồn GPS


đặt lại chế độ GPS(Hot/Warm/Cold)


nhận thông tin vị trí GPS hiện tại


điều khiển dữ liệu ra NMEA GPS


Tình trạng GPS


set tốc độ baudrate


     1.2 AT+CGPSPWR:

 a. Test command:




      Feedback: +CGPSPWR


 b. Read command:






  c. The order of recording:




    [mode]: 0 Power off GPS


    [mode]: 1 Power on GPS


     1.3 AT+CGPSRST:


    a. Test command:




    Feedback: +CGPSRST:(danh sách các mode)


     a. Read command:




     Feedback:  +CGPSRST:[mode]


    c. The order of recording:




     [mode]: 0 reset GPS in COLD start mode


     [mode]: 1 auto mode 


      COLD mode is recommended for the first time


      1.4 AT+CGPSINF:


      a. Test command:




     Feedback:  +CGPSINF:(0,2,4,8,16,32,64,128)


    b. Read command:




    If [mode] is 0: 




  [mode], [latitude], [height], [UTC time], [TTFF], [num], [speed], [course]


     If [mode] is:


    21: Parameters see appendix A.1 “$GPGGA” [1]


    22: Parameters see appendix A.2 “GPGLL” [1]


    23: Parameters see appendix A.3 “GPGSA” [1]


    24: Parameters see appendix A.4 “GPGSV” [1][2]


    25: Parameters see appendix A.5 “GPRMC” [1]


    26: Parameters see appendix A.6 “GPVTG” [1]


    27: Parameters see appendix A.7 “GPZDA” [1]


    [1] Excluding parameters: ”massage ID”, “checksum”, “[CR][LF]”


    [2] includes parameters:


Satellites in view

Satellites ID





    1.5 AT+CGPSOUT:

     a. Test command




      Feedback:  +CGPSOUT:(0-255)


     b. Read command




    Feedback: +CGPSOUT:[mode]


    c. The order of recording:




    If is 0: Minimize GPS NMEA output information from Debug UART




    Bit1=1, For NMEA $ GPGGA output data, see annex A.1


    Bit2=1, For NMEA $ GPGGA output data, see annex A.2


    Bit3=1, For NMEA $ GPGGA output data, see annex A.3


    Bit4=1, For NMEA $ GPGGA output data, see annex A.4


    Bit5=1, For NMEA $ GPGGA output data, see annex A.5


     Bit6=1, For NMEA $ GPGGA output data, see annex A.6


     Bit7=1, For NMEA $ GPGGA output data, see annex A.7




    a. Test command




    Feedback: +CGPSSTATUS:(danh sách các mode )


     b.Read command:




    Feedback:  +AT+CGPSSTATUS: [mode]

    GPS MODE RESET parameters


      [mode] is a string value


      "Location UnKnown": GPS is not running


      "Location Not Fix": GPS is running and not fixed


       "Location 2D Fix": Fixed 2D GPS status


      "Location 3D Fix": GPS fixed 3D position

     1.7 AT+CGPSIPR:


    a. Test command:




  Feedback: +CGPSIPR:(danh sách mode)


   b.Read command:




  c. The order of recording:




   [mode]: 4800,9600,19200,38400,57600,115200,230400,460800


     AT-COM shows you how we can get GPS coordinates from satellites and display them on the LCD. Based on that, you can develop higher-level applications with ease.

    Hardware block diagram as star:




       The processor block uses the microprocessor to control the sim908 module and to process the sim module signal returned. Also, when receiving a microprocessor coordinate signal, it will display the content to the LCD.

       Sim 908 can receive the signal sent by the satellite thanks to the GPS antenna.




  This signal will be transmitted continuously down the processor if we use the sim's GPS.

      Diagram of each block principle:





                                                                                                    KHỐI MAX232



Some pictures of the actual operation of the circuit: