Some debug.

api/modem/gps/check.go

@@ -10,7 +10,7 @@ func (g *gps) CheckStatus() error {
 	// Provides more information about signal and possible problems using NMEA reports
 
 	// Collect reports
-	reports, err := g.collectNmeaReports(gpgsv | gpgsa) // Now minimum
+	reports, err := g.collectNmeaReports(nmeaFlagsAll) // Now minimum
 	if err != nil {
 		return fmt.Errorf("collect nmea reports: %w", err)
 	}

api/modem/gps/gps.go

@@ -31,7 +31,7 @@ func New(logger *log.Logger, port at.Port) Gps {
 }
 
 func (g *gps) Init() error {
-	if g.port.IsConnected() {
+	if !g.port.IsConnected() {
 		return fmt.Errorf("at port is not connected")
 	}
 	return nil

api/modem/gps/nmea.go

@@ -33,17 +33,17 @@ const (
 )
 
 // Go... otherwise will throw warning
-var _ = gga | rmc | gpgsv | gpgsa | vtg | xfi | glgsa | gns | gagsv | bdpqgsa | bdpqgsv
+var nmeaFlagsAll = gga | rmc | gpgsv | gpgsa | vtg | xfi | glgsa | gns | gagsv | bdpqgsa | bdpqgsv
 
 func (g *gps) rawCollect(flags nmeaFlags) (string, error) {
 	// Need to omplement low level write/read here because collect must be atomic operation
 	// If other command is executed(write/read) it will read a part of nmea report and cause an error
+	g.switchGpsMode(true)
 	g.port.Mutex().Lock()
 	s := g.port.SerialPort()
 	defer func() {
-		s.ResetInputBuffer()
-		s.ResetOutputBuffer()
 		g.port.Mutex().Unlock()
+		g.switchGpsMode(false)
 	}()
 
 	// Send AT+CGPSINFOCFG=255, flags
@@ -57,7 +57,7 @@ func (g *gps) rawCollect(flags nmeaFlags) (string, error) {
 	time.Sleep(collectTimeout)
 
 	// Send AT+CGPSINFOCFG=0, flags
-	if _, err := s.Write([]byte("AT+CGPSINFOCFG=255," + string(flags) + "\r\n")); err != nil {
+	if _, err := s.Write([]byte("AT+CGPSINFOCFG=0," + string(flags) + "\r\n")); err != nil {
 		return "", fmt.Errorf("serial port write 2: %w", err)
 	}