Add network device driver model, netdev

examples/net/ntpclient/main.go

@@ -0,0 +1,104 @@
+// This is an example of an NTP client.
+//
+// It creates a UDP connection to request the current time and parse the
+// response from a NTP server.  The system time is set to NTP time.
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"machine"
+	"net"
+	"runtime"
+	"time"
+)
+
+var (
+	ssid string
+	pass string
+	// IP address of the server aka "hub". Replace with your own info.
+	ntpHost string = "0.pool.ntp.org:123"
+)
+
+const NTP_PACKET_SIZE = 48
+
+var response = make([]byte, NTP_PACKET_SIZE)
+
+func main() {
+
+	waitSerial()
+
+	if err := netdev.NetConnect(); err != nil {
+		log.Fatal(err)
+	}
+
+	conn, err := net.Dial("udp", ntpHost)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	println("Requesting NTP time...")
+
+	t, err := getCurrentTime(conn)
+	if err != nil {
+		log.Fatal(fmt.Sprintf("Error getting current time: %v", err))
+	} else {
+		message("NTP time: %v", t)
+	}
+
+	conn.Close()
+	netdev.NetDisconnect()
+
+	runtime.AdjustTimeOffset(-1 * int64(time.Since(t)))
+
+	for {
+		message("Current time: %v", time.Now())
+		time.Sleep(time.Minute)
+	}
+}
+
+// Wait for user to open serial console
+func waitSerial() {
+	for !machine.Serial.DTR() {
+		time.Sleep(100 * time.Millisecond)
+	}
+}
+
+func getCurrentTime(conn net.Conn) (time.Time, error) {
+	if err := sendNTPpacket(conn); err != nil {
+		return time.Time{}, err
+	}
+
+	n, err := conn.Read(response)
+	if err != nil && err != io.EOF {
+		return time.Time{}, err
+	}
+	if n != NTP_PACKET_SIZE {
+		return time.Time{}, fmt.Errorf("expected NTP packet size of %d: %d", NTP_PACKET_SIZE, n)
+	}
+
+	return parseNTPpacket(response), nil
+}
+
+func sendNTPpacket(conn net.Conn) error {
+	var request = [48]byte{
+		0xe3,
+	}
+
+	_, err := conn.Write(request[:])
+	return err
+}
+
+func parseNTPpacket(r []byte) time.Time {
+	// the timestamp starts at byte 40 of the received packet and is four bytes,
+	// this is NTP time (seconds since Jan 1 1900):
+	t := uint32(r[40])<<24 | uint32(r[41])<<16 | uint32(r[42])<<8 | uint32(r[43])
+	const seventyYears = 2208988800
+	return time.Unix(int64(t-seventyYears), 0)
+}
+
+func message(format string, args ...interface{}) {
+	println(fmt.Sprintf(format, args...), "\r")
+}