# NEW LOG
# format=1.0.0nano
$BNRDD,204,2012-09-20T16:53:58Z,776,63,33895,A,5641.7788,N,1411.8820,E,9861.20,A,109,9*46
$BNRDD,[4digit_device_id],[ISO8601_time],[cpm],[cpb],[total_count],[geiger_status],[lat],[NS],[long],[WE],[altitude],[gps_status],[nbsat],[precision]


  // prepare the log entry
  memset(buf, 0, LINE_SZ);
  sprintf_P(buf, PSTR("$%s,%04d,%02d-%02d-%02dT%02d:%02d:%02dZ,%ld,%ld,%ld,%c,%s,%c,%s,%c,%s,%c,%d,%ld"),  \
              NANO_HEADER, \
              config.device_id, \
              year, month, day,  \
              hour, minute, second, \
              cpm, \
              cpb, \
              total_count, \
              geiger_status, \
              lat, NS,\
              lon, WE,\
              strbuffer, \
              gps_status, \
              nbsat  == TinyGPS::GPS_INVALID_SATELLITES ? 0 : nbsat, \
              precission == TinyGPS::GPS_INVALID_HDOP ? 0 : precission);

  len = strlen(buf);
  buf[len] = '\0';

  // generate checksum
  chk = checksum(buf+1, len);

  // add checksum to end of line before sending
  if (chk < 16)
    sprintf_P(buf + len, PSTR("*0%X"), (int)chk);
  else
    sprintf_P(buf + len, PSTR("*%X"), (int)chk);
	
	
/* compute check sum of N bytes in array s */
char checksum(char *s, int N)
{
  int i = 0;
  char chk = s[0];

  for (i=1 ; i < N ; i++)
    chk ^= s[i];	// opérateur bit à  bit XOR

  return chk;
}