Added draft GPS checks though NMEA reports.

api/modem/at/at.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"sync"
 	"time"
 
 	"go.bug.st/serial"
@@ -18,6 +19,8 @@ const (
 type atPort struct {
 	logger *log.Logger
 
+	mutex sync.Mutex // Mutex for all operation with serial port
+
 	baudrate int
 	portName string
 	port     serial.Port
@@ -27,7 +30,8 @@ type atPort struct {
 type Port interface {
 	GetName() string
 	GetBaudrate() int
-	GetSerialPort() serial.Port // For extra need
+	SerialPort() serial.Port // For extra need
+	Mutex() sync.Locker      // retruns pointer to mutex for advanced use like readign NMEA reports
 
 	Connect() error
 	Disconnect() error
@@ -56,11 +60,18 @@ func (p *atPort) GetBaudrate() int {
 	return p.baudrate
 }
 
-func (p *atPort) GetSerialPort() serial.Port {
+func (p *atPort) SerialPort() serial.Port {
 	return p.port
 }
 
+func (p *atPort) Mutex() sync.Locker {
+	return &p.mutex
+}
+
 func (p *atPort) Connect() error {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+
 	p.logger.Println("Connecting to", p.portName, "...")
 	s, err := serial.Open(p.portName, &serial.Mode{BaudRate: p.baudrate})
 	if err != nil {
@@ -76,8 +87,10 @@ func (p *atPort) Connect() error {
 }
 
 func (p *atPort) Disconnect() error {
+	p.mutex.Lock()
 	defer func() {
 		p.port = nil
+		p.mutex.Unlock()
 	}()
 	if err := p.port.Close(); err != nil {
 		return fmt.Errorf("close port: %w", err)
@@ -86,16 +99,22 @@ func (p *atPort) Disconnect() error {
 }
 
 func (p *atPort) IsConnected() bool {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+
 	return p.port != nil
 }
 
 // Low level write/read function
 func (p *atPort) RawSend(msg string) (string, error) {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+
 	// Write
 	if _, err := p.port.Write([]byte(msg)); err != nil {
 		return "", fmt.Errorf("serial port write: %w", err)
 	}
-	time.Sleep(time.Millisecond)
+	// time.Sleep(time.Millisecond)
 	// Read
 	readLen, err := p.port.Read(p.inputBuf)
 	// p.logger.Println(msg, "\x1b[38;2;150;150;150mRAWREAD:", string(p.inputBuf[:readLen]), "\x1b[38;2;255;255;255m")
@@ -121,5 +140,8 @@ func (p *atPort) Send(cmd string) (Resp, error) {
 }
 
 func (p *atPort) Close() error {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+
 	return p.port.Close()
 }