initial commit

controller/relay/relay.go

@@ -0,0 +1,82 @@
+package relay
+
+import (
+	"fmt"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// CH341 serial relay protocol (LCUS-type modules on /dev/ttyUSBx).
+//
+// Command format:
+//   ON:  0xA0 <channel> 0x01 <checksum>
+//   OFF: 0xA0 <channel> 0x00 <checksum>
+//   checksum = (0xA0 + channel + state) & 0xFF
+
+type Relay struct {
+	devicePath string
+	channel    byte
+	baud       int
+}
+
+func New(devicePath string, channel, baud int) *Relay {
+	return &Relay{
+		devicePath: devicePath,
+		channel:    byte(channel),
+		baud:       baud,
+	}
+}
+
+func (r *Relay) Set(on bool) error {
+	f, err := os.OpenFile(r.devicePath, os.O_RDWR|unix.O_NOCTTY, 0)
+	if err != nil {
+		return fmt.Errorf("relay open %s: %w", r.devicePath, err)
+	}
+	defer f.Close()
+
+	fd := int(f.Fd())
+	if err := configureSerial(fd, r.baud); err != nil {
+		return fmt.Errorf("relay serial config: %w", err)
+	}
+
+	var state byte
+	if on {
+		state = 0x01
+	}
+
+	checksum := (0xA0 + r.channel + state) & 0xFF
+	cmd := []byte{0xA0, r.channel, state, checksum}
+
+	if _, err := f.Write(cmd); err != nil {
+		return fmt.Errorf("relay write: %w", err)
+	}
+
+	return nil
+}
+
+func (r *Relay) Close() error {
+	return nil
+}
+
+func configureSerial(fd, baud int) error {
+	baudRate, ok := baudRates[baud]
+	if !ok {
+		return fmt.Errorf("unsupported baud rate: %d", baud)
+	}
+
+	var t unix.Termios
+	t.Cflag = unix.CS8 | unix.CLOCAL | unix.CREAD | baudRate
+	t.Cc[unix.VMIN] = 1
+	t.Cc[unix.VTIME] = 0
+
+	return unix.IoctlSetTermios(fd, unix.TCSETS, &t)
+}
+
+var baudRates = map[int]uint32{
+	9600:   unix.B9600,
+	19200:  unix.B19200,
+	38400:  unix.B38400,
+	57600:  unix.B57600,
+	115200: unix.B115200,
+}