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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package main contains a program that displays the IPv4 address
// of the machine on an a Grove-LCD RGB backlight.
package main
import (
"fmt"
"net"
"golang.org/x/exp/io/i2c"
)
const (
DISPLAY_RGB_ADDR = 0x62
DISPLAY_TEXT_ADDR = 0x3e
)
func main() {
d, err := i2c.Open(&i2c.Devfs{Dev: "/dev/i2c-1"}, DISPLAY_RGB_ADDR)
if err != nil {
panic(err)
}
td, err := i2c.Open(&i2c.Devfs{Dev: "/dev/i2c-1"}, DISPLAY_TEXT_ADDR)
if err != nil {
panic(err)
}
// Set the backlight color to 100,100,100.
write(d, []byte{0, 0})
write(d, []byte{1, 0})
write(d, []byte{0x08, 0xaa})
write(d, []byte{4, 100}) // R value
write(d, []byte{3, 100}) // G value
write(d, []byte{2, 100}) // B value
ip, err := resolveIP()
if err != nil {
panic(err)
}
fmt.Printf("host machine IP is %v\n", ip)
write(td, []byte{0x80, 0x02}) // return home
write(td, []byte{0x80, 0x01}) // clean the display
write(td, []byte{0x80, 0x08 | 0x04}) // no cursor
write(td, []byte{0x80, 0x28}) // two lines
for _, s := range ip {
write(td, []byte{0x40, byte(s)})
}
}
func write(d *i2c.Device, buf []byte) {
err := d.Write(buf)
if err != nil {
panic(err)
}
}
func resolveIP() (string, error) {
var ip net.IP
ifaces, err := net.Interfaces()
if err != nil {
panic(err)
}
for _, i := range ifaces {
addrs, err := i.Addrs()
if err != nil {
panic(err)
}
for _, addr := range addrs {
switch v := addr.(type) {
case *net.IPNet:
ip = v.IP
case *net.IPAddr:
ip = v.IP
}
ip = ip.To4()
if ip != nil && ip.String() != "127.0.0.1" {
return ip.String(), nil
}
}
}
return "", fmt.Errorf("cannot resolve the IP")
}
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