static void MainFormRefresh(FormType *frmP) {
  Err errPVT;
  GPSPVTDataType pvt;
  UInt16 libVersion = 0;
  UInt8 maxSats = 0;
  LatLongComp LatLong;
  float lat, lon;

  Char UTC[9];
  Int16 secs, mins, hours;

  HIDEOBJECTID(frmP, MainFix2DLabel);
  HIDEOBJECTID(frmP, MainFix2DDiffLabel);
  HIDEOBJECTID(frmP, MainFix3DLabel);
  HIDEOBJECTID(frmP, MainFix3DDiffLabel);
  HIDEOBJECTID(frmP, MainFixUnusableLabel);
  HIDEOBJECTID(frmP, MainFixInvalidLabel);
  if (mggGarminIsOpen) {
    libVersion = GPSGetLibAPIVersion(mggGarminLibRef);
    maxSats = GPSGetMaxSatellites(mggGarminLibRef);
    errPVT = GPSGetPVT(mggGarminLibRef, &pvt);
    //err = GPSGetTime(mggGarminLibRef, &time);
    //err = GPSGetPosition(mggGarminLibRef, &position);
    //err = GPSGetVelocity(mggGarminLibRef, &velocity);

    SetFieldFromUInt16(frmP, MainAPIVersionField, libVersion);
    SetFieldFromUInt16(frmP, MainMaxSatsField, (UInt16) maxSats);

    switch (pvt.status.mode) {
    case gpsModeOff:
      SetFieldTextFromStr(frmP, MainGPSModeField, "GPS Off"); break;
    case gpsModeNormal:
      SetFieldTextFromStr(frmP, MainGPSModeField, "GPS normal"); break;
    case gpsModeBatSaver:
      SetFieldTextFromStr(frmP, MainGPSModeField, "battery save mode"); break;
    case gpsModeSim:
      SetFieldTextFromStr(frmP, MainGPSModeField, "simulated GPS"); break;
    case gpsModeExternal:
      SetFieldTextFromStr(frmP, MainGPSModeField, "external GPS"); break;
    }
    switch (pvt.status.fix) {
    case gpsFixUnusable:
      SHOWOBJECTID(frmP, MainFixUnusableLabel); break;
    case gpsFixInvalid:
      SHOWOBJECTID(frmP, MainFixInvalidLabel); break;
    case gpsFix2D:
      SHOWOBJECTID(frmP, MainFix2DLabel); break;
    case gpsFix2DDiff:
      SHOWOBJECTID(frmP, MainFix2DDiffLabel); break;
    case gpsFix3D:
      SHOWOBJECTID(frmP, MainFix3DLabel); break;
    case gpsFix3DDiff:
      SHOWOBJECTID(frmP, MainFix3DDiffLabel); break;
    }

    if (errPVT == gpsErrNone && (pvt.status.fix >= gpsFix2D)) {
      SetFieldFromFloat(frmP, MainEPETotalField, pvt.status.epe * METERS_TO_FEET, 1);
      SetFieldFromFloat(frmP, MainEPEhorizField, pvt.status.eph * METERS_TO_FEET, 1);
      SetFieldFromFloat(frmP, MainEPEvertField, pvt.status.epv * METERS_TO_FEET, 1);

      SetFieldFromInt32(frmP, MainLatSemicField, pvt.position.lat);
      SetFieldFromInt32(frmP, MainLonSemicField, pvt.position.lon);
      lat = pvt.position.lat * SemicirclesToDegrees;
      lon = pvt.position.lon * SemicirclesToDegrees;
      LATLONGCOMPINIT(&LatLong, lat, lon);
      ShowAngleInField(frmP, MainLatField, &LatLong.lat);
      ShowAngleInField(frmP, MainLonField, &LatLong.lon);

      hours = pvt.time.seconds / 3600L;
      mins = (pvt.time.seconds / 60L) - (hours * 60);
      secs = pvt.time.seconds - ((hours*3600L) + (mins*60L));
      StrPrintF(UTC, "%02d:%02d:%02d", hours, mins, secs);
      SetFieldTextFromStr(frmP, MainTimeField, UTC);

      SetFieldFromFloat(frmP, MainMSLelevField, pvt.position.altMSL * METERS_TO_FEET, 1);
      SetFieldFromFloat(frmP, MainWGS84elevField, pvt.position.altWGS84 * METERS_TO_FEET, 1);

      SetFieldFromFloat(frmP, MainTrackField, pvt.velocity.track * RADTODEG, 1);
      SetFieldFromFloat(frmP, MainSpeedField, pvt.velocity.speed, 1);

      SetFieldFromFloat(frmP, MainVeloNorthField, pvt.velocity.north, 1);
      SetFieldFromFloat(frmP, MainVeloEastField, pvt.velocity.east, 1);
      SetFieldFromFloat(frmP, MainVeloUpField, pvt.velocity.up, 1);
    }
    else {
      SetFieldTextFromStr(frmP, MainEPETotalField, "");
      SetFieldTextFromStr(frmP, MainEPEhorizField, "");
      SetFieldTextFromStr(frmP, MainEPEvertField, "");

      SetFieldTextFromStr(frmP, MainLatField, "");
      SetFieldTextFromStr(frmP, MainLonField, "");
      SetFieldTextFromStr(frmP, MainLatSemicField, "");
      SetFieldTextFromStr(frmP, MainLonSemicField, "");

      SetFieldTextFromStr(frmP, MainTimeField, "");

      SetFieldTextFromStr(frmP, MainMSLelevField, "");
      SetFieldTextFromStr(frmP, MainWGS84elevField, "");

      SetFieldTextFromStr(frmP, MainTrackField, "");
      SetFieldTextFromStr(frmP, MainSpeedField, "");

      SetFieldTextFromStr(frmP, MainVeloUpField, "");
      SetFieldTextFromStr(frmP, MainVeloNorthField, "");
      SetFieldTextFromStr(frmP, MainVeloEastField, "");
    }
  }
  else if (mggIsaGarmin)
    _Debug("lib not open");
  else
    _Debug("not a Garmin");
}


--------------------------------------
GarminUtils.c

#include "GPSLib68k.h"
#include "mgGarminUtils.h"

UInt16 mggGarminLibRef;
Boolean mggGarminIsOpen;
Boolean mggIsaGarmin;

Err OpenGarminLibrary(void) {
  /*-------------------------------------------
    Find the GPS library. If not found, load it.
    -------------------------------------------*/

  Err err;
  UInt32 companyID;

  mggGarminIsOpen = false;
  err = FtrGet(sysFtrCreator, sysFtrNumOEMCompanyID, &companyID);
  if (companyID != 'grmn')
        mggIsaGarmin = false;
  else
        mggIsaGarmin = true;

  err = SysLibFind(gpsLibName,  &mggGarminLibRef);
  if (err)
    {
      err = SysLibLoad( gpsLibType, gpsLibCreator, &mggGarminLibRef);
    }
  err = GPSOpen(mggGarminLibRef);
  if (!err)
     mggGarminIsOpen = true;
  else
     _Debug2("libopen", "GPSOpen() failed");

  return err;
}

void CloseGarminLibrary(void) {
    Err err;

      if (!mggGarminIsOpen)
    return;

        err = GPSClose(mggGarminLibRef);
      if( err != gpsErrStillOpen )
        {
            SysLibRemove( mggGarminLibRef );
        }
}

--------------------------------------
GarminUtils.h

#include "GPSLib68K.h"

#define SemicirclesToDegrees (180./2147483648.);
extern UInt16 mggGarminLibRef;
extern Boolean mggGarminIsOpen;
extern Boolean mggIsaGarmin;

Err OpenGarminLibrary(void);
void CloseGarminLibrary(void);