File content as of revision 2:2b6b55edb50c:

/*
このプログラムはNEO-7MからUBX形式でUARTを介して位置、速度(NAV-VELNED)、測位状態(NAV-STATUS)を読み取るプログラムである。
*/

#include "mbed.h"

DigitalOut myled(LED1);

// serial port
Serial pc(USBTX, USBRX); // tx, rx
Serial ublox_ubx(p9,p10);//tx,rx

//variables for decodeing 
float latitude,longitude,height_float;
int gps_Fix;
float velN_float,velE_float,velD_float;

int flag_posllh,flag_velned;//UBXデータを処理したかどうかのフラグ

//処理時間計測の為のタイマー
Timer processing_timer;
//処理時間
int processed_time,processed_time_before,processed_time_after;

//Header char
const unsigned char UBX_HEADER[]        = { 0xB5, 0x62 };
const unsigned char NAV_POSLLH_HEADER[] = { 0x01, 0x02 };
const unsigned char NAV_STATUS_HEADER[] = { 0x01, 0x03 };

const unsigned char NAV_VELNED_HEADER[] = { 0x01, 0x12 };

//
enum _ubxMsgType {
  MT_NONE,
  MT_NAV_POSLLH,
  MT_NAV_STATUS,
  MT_NAV_VELNED
};

struct NAV_POSLLH {
  unsigned char cls;
  unsigned char id;
  unsigned short len;
  unsigned long iTOW;
  long lon;
  long lat;
  long height;
  long hMSL;
  unsigned long hAcc;
  unsigned long vAcc;
};

struct NAV_STATUS {
  unsigned char cls;
  unsigned char id;
  unsigned short len;
  unsigned long iTOW;
  unsigned char gpsFix;
  char flags;
  char fixStat;
  char flags2;
  unsigned long ttff;
  unsigned long msss;
};

struct NAV_VELNED  {
  unsigned char cls;
  unsigned char id;
  unsigned short len;
  unsigned long iTOW;
  signed long velN;
  signed long velE;
  signed long velD;
  unsigned long speed;
  unsigned long gSpeed;
  signed long heading;
  unsigned long sAcc;
  unsigned long cAcc;
    
};

union UBXMessage {
  NAV_VELNED navVelned;//payload size is 36bytes
  NAV_POSLLH navPosllh;//payload size is 28bytes
  NAV_STATUS navStatus;//payload size is 16bytes
};

UBXMessage ubxMessage;

// The last two bytes of the message is a checksum value, used to confirm that the received payload is valid.
// The procedure used to calculate this is given as pseudo-code in the uBlox manual.
void calcChecksum(unsigned char* CK, int msgSize) {
  memset(CK, 0, 2);
  for (int i = 0; i < msgSize; i++) {
    CK[0] += ((unsigned char*)(&ubxMessage))[i];
    CK[1] += CK[0];
  }
}

// Compares the first two bytes of the ubxMessage struct with a specific message header.
// Returns true if the two bytes match.
bool compareMsgHeader(const unsigned char* msgHeader) {
  unsigned char* ptr = (unsigned char*)(&ubxMessage);
  return ptr[0] == msgHeader[0] && ptr[1] == msgHeader[1];
}

// Reads in bytes from the GPS module and checks to see if a valid message has been constructed.
// Returns the type of the message found if successful, or MT_NONE if no message was found.
// After a successful return the contents of the ubxMessage union will be valid, for the 
// message type that was found. Note that further calls to this function can invalidate the
// message content, so you must use the obtained values before calling this function again.
int processGPS() {
  
  static int fpos = 0;
  static unsigned char checksum[2];
  
  static unsigned char currentMsgType = MT_NONE;
  static int payloadSize = sizeof(UBXMessage);
  
  processed_time_before = processing_timer.read_us();// captureing prossing time
  
  while ( ublox_ubx.readable() ) {
    
    unsigned char c = ublox_ubx.getc();    
    //Serial.write(c);
    
    if ( fpos < 2 ) {
      // For the first two bytes we are simply looking for a match with the UBX header bytes (0xB5,0x62)
      if ( c == UBX_HEADER[fpos] )
        fpos++;
      else
        fpos = 0; // Reset to beginning state.
    }
    else {
      // If we come here then fpos >= 2, which means we have found a match with the UBX_HEADER
      // and we are now reading in the bytes that make up the payload.
      
      // Place the incoming byte into the ubxMessage struct. The position is fpos-2 because
      // the struct does not include the initial two-byte header (UBX_HEADER).
      if ( (fpos-2) < payloadSize )
        ((unsigned char*)(&ubxMessage))[fpos-2] = c;

      fpos++;
      
      if ( fpos == 4 ) {
        // We have just received the second byte of the message type header, 
        // so now we can check to see what kind of message it is.
        
        if ( compareMsgHeader(NAV_VELNED_HEADER) ) {
          currentMsgType = MT_NAV_VELNED;
          payloadSize = sizeof(NAV_VELNED);
          
        }
        else if ( compareMsgHeader(NAV_STATUS_HEADER) ) {
          currentMsgType = MT_NAV_STATUS;
          payloadSize = sizeof(NAV_STATUS);
        }
        
        else if ( compareMsgHeader(NAV_POSLLH_HEADER) ) {
          currentMsgType = MT_NAV_POSLLH;
          payloadSize = sizeof(NAV_POSLLH);
          
        }
        
        else {
          // unknown message type, bail
          fpos = 0;
          continue;
        }
      }

      if ( fpos == (payloadSize+2) ) {
        // All payload bytes have now been received, so we can calculate the 
        // expected checksum value to compare with the next two incoming bytes.
        calcChecksum(checksum, payloadSize);
      }
      else if ( fpos == (payloadSize+3) ) {
        // First byte after the payload, ie. first byte of the checksum.
        // Does it match the first byte of the checksum we calculated?
        if ( c != checksum[0] ) {
          // Checksum doesn't match, reset to beginning state and try again.
          fpos = 0; 
        }
      }
      else if ( fpos == (payloadSize+4) ) {
        // Second byte after the payload, ie. second byte of the checksum.
        // Does it match the second byte of the checksum we calculated?
        fpos = 0; // We will reset the state regardless of whether the checksum matches.
        if ( c == checksum[1] ) {
          // Checksum matches, we have a valid message.
          if(currentMsgType==MT_NAV_POSLLH){
             latitude=ubxMessage.navPosllh.lat/10000000.0f;
             longitude=ubxMessage.navPosllh.lon/10000000.0f;
             height_float=float(ubxMessage.navPosllh.height);
             flag_posllh=1;
              }
          else if(currentMsgType==MT_NAV_VELNED){
              velN_float=float(ubxMessage.navVelned.velN);
              velE_float=float(ubxMessage.navVelned.velE);
              velD_float=float(ubxMessage.navVelned.velD);
              flag_velned=1;
              
              }
          else if(currentMsgType==MT_NAV_STATUS){
              
              }
          
          return currentMsgType; 
        }
      }
      else if ( fpos > (payloadSize+4) ) {
        // We have now read more bytes than both the expected payload and checksum 
        // together, so something went wrong. Reset to beginning state and try again.
        fpos = 0;
      }
    }
  }
   processed_time_after = processing_timer.read_us();// captureing prossing time
   processed_time=processed_time_after-processed_time_before;
   
  return MT_NONE;
}

/*--------------------------------------------*/
int main() {
    
    //UART initialization
    pc.baud(115200); //115.2 kbps
    ublox_ubx.baud(115200); //115.2 kbps
    
    flag_posllh=0;
    flag_velned=0;
    
    processing_timer.start();//timer starts
    
    while(1) {
        int msgType = processGPS();
        
        if((flag_posllh==1)&&(flag_velned==1)){
            
            /*Teratermでロギングする用の表示*/
            pc.printf("%f,%f,%f,%f,%f,%f\r\n",latitude,longitude,height_float,velN_float,velE_float,velD_float);
            /*計測ではなくデバッグ用の表示*/
            //pc.printf("latitude=%f,longitude=%f,height=%f\r\n",latitude,longitude,height_float);
            //pc.printf("velN=%f,velE=%f,velD=%f\r\n",velN_float,velE_float,velD_float);
            //pc.printf("processed_time(us)=%d\r\n",processed_time);
            
            
            /*processGPSの処理時間の表示*/
            //pc.printf("processed_time_before(us)=%d\r\n",(processed_time_before));
            //pc.printf("processed_time_after(us)=%d\r\n",(processed_time_after));
            
            /*フラグを0に戻す*/
            flag_posllh=0;
            flag_velned=0;
            
            }
        else{}
        /*
          if ( msgType == MT_NAV_POSLLH ) {
             latitude=ubxMessage.navPosllh.lat/10000000.0f;
             longitude=ubxMessage.navPosllh.lon/10000000.0f;
             height_float=float(ubxMessage.navPosllh.height);
             
             pc.printf("latitude=%f,longitude=%f,height=%f\r\n",latitude,longitude,height_float);
          }
          else if ( msgType == MT_NAV_STATUS ) {
              gps_Fix=int(ubxMessage.navStatus.gpsFix);
              pc.printf("gps_Fix=%d\r\n",gps_Fix);
              }
          else if ( msgType == MT_NAV_VELNED ) {
              velN_float=float(ubxMessage.navVelned.velN);
              velE_float=float(ubxMessage.navVelned.velE);
              velD_float=float(ubxMessage.navVelned.velD);
              //pc.printf("velN=%f,velE=%f,velD=%f\r\n",velN_float,velE_float,velD_float);
              //Tera termでNED座標系での速度履歴を保存したい場合、以下のコメント出力を用いる。
              pc.printf("%f,%f,%f\r\n",velN_float,velE_float,velD_float);
              }
        */
              
        }//while
  
}