MTK3339.h

00001 // Header to represent serial interface to MTK3339 GPS chip
00002 // Original author: Embedded Artists
00003 // Revised by T. Bronez, 2015-07-31
00004 
00005 #ifndef MTK3339_H
00006 #define MTK3339_H
00007 #include <time.h>
00008 
00009 /** 
00010  * An interface to the MTK3339 GPS module.
00011  */
00012 class MTK3339 {
00013 public:
00014 
00015     enum NmeaSentence {
00016         NMEA_NONE = 0x00,
00017         NMEA_GGA  = 0x01,
00018         NMEA_GSA  = 0x02,
00019         NMEA_GSV  = 0x04,
00020         NMEA_RMC  = 0x08,
00021         NMEA_VTG  = 0x10
00022     };
00023        
00024     struct RmcType {
00025         char status;        // A valid, V invalid, blank unknown
00026         double lat_dd;      // latitude in decimal degrees
00027         double lon_dd;      // longitude in decimal degrees
00028         struct tm gps_tm;   // date and time (to seconds)
00029         int msec;           // millseconds
00030     };
00031     
00032     /** 
00033      * Create an interface to the MTK3339 GPS module
00034      *
00035      * @param tx UART TX line pin
00036      * @param rx UART RX line pin
00037      */
00038     MTK3339(PinName tx, PinName rx);
00039          
00040     /** 
00041      * Start to read data from the GPS module.
00042      * 
00043      * @param fptr A pointer to a void function that will be called when there 
00044      * is data available. 
00045      * @param mask specifies which sentence types (NmeaSentence) that are of 
00046      * interest. The callback function will only be called for messages 
00047      * specified in this mask.
00048      */     
00049     void start(void (*fptr)(void), int mask);
00050 
00051     /** 
00052      * Start to read data from the GPS module.
00053      * 
00054      * @param tptr pointer to the object to call the member function on
00055      * @param mptr pointer to the member function to be called
00056      * @param mask specifies which sentence types (NmeaSentence) that are of 
00057      * interest. The member function will only be called for messages 
00058      * specified in this mask.
00059      */        
00060     template<typename T>
00061     void start(T* tptr, void (T::*mptr)(void), int mask) {
00062         if((mptr != NULL) && (tptr != NULL) && mask) {
00063             _dataCallback.attach(tptr, mptr);
00064             _sentenceMask = mask;
00065             _serial.attach(this, &MTK3339::uartIrq, Serial::RxIrq);            
00066         }
00067     }    
00068     
00069     /** 
00070      * Stop to read data from GPS module
00071      */
00072     void stop();
00073     
00074     /** 
00075      * Get the type of the data reported in available data callback.
00076      * This method will only return a valid type when called within the
00077      * callback. 
00078      */    
00079     NmeaSentence getAvailableDataType();
00080 
00081     /**
00082      * Time, position and date related data
00083      */
00084     enum PubConstants {
00085         MSG_BUF_SZ = 100
00086     };
00087     // Leave room for a terminating \0 in each buffer
00088     char ggaMsg[MSG_BUF_SZ+1];  // longest observed strlen = 72
00089     char gsaMsg[MSG_BUF_SZ+1];  // longest observed strlen = 56
00090     char gsvMsg[MSG_BUF_SZ+1];  // longest observed strlen = 68
00091     char rmcMsg[MSG_BUF_SZ+1];  // longest observed strlen = 70
00092     char vtgMsg[MSG_BUF_SZ+1];  // longest observed strlen = 37
00093 
00094     RmcType rmc;
00095     void decodeRMC ();
00096 
00097 private:
00098 
00099     enum PrivConstants {
00100         MTK3339_BUF_SZ = 255
00101     };
00102     
00103     enum DataState {
00104         StateStart = 0,
00105         StateData
00106     };
00107     
00108     FunctionPointer _dataCallback;
00109     char _buf[MTK3339_BUF_SZ];
00110     int _bufPos;
00111     DataState _state;
00112     int _sentenceMask;
00113     NmeaSentence _availDataType;
00114     Serial _serial;
00115 
00116     void saveRMC(char* data, int dataLen);
00117     void saveGGA(char* data, int dataLen);
00118     void saveGSA(char* data, int dataLen);
00119     void saveGSV(char* data, int dataLen);
00120     void saveVTG(char* data, int dataLen);
00121     void saveData(char* data, int len);
00122     void uartIrq();
00123 
00124 };
00125 
00126 #endif
00127