// Configure configures f as a 8N1 serial port with the specified baudrate.
func Configure(f fder, baudrate uint32) error {
var termios syscall.Termios
if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(f.Fd()), uintptr(syscall.TCGETS), uintptr(unsafe.Pointer(&termios))); err != 0 {
return err
}
termios.Ispeed = baudrate
termios.Ospeed = baudrate
termios.Cflag &^= CBAUD
termios.Cflag &^= CBAUDEX
termios.Cflag |= baudrate
// set 8N1
termios.Cflag &^= syscall.PARENB
termios.Cflag &^= syscall.CSTOPB
termios.Cflag &^= syscall.CSIZE
termios.Cflag |= syscall.CS8
// Local connection, no modem control
termios.Cflag |= (syscall.CLOCAL | syscall.CREAD)
// Disable hardware flow control
termios.Cflag &^= CRTSCTS
// Block on a zero read (instead of returning EOF)
termios.Cc[syscall.VMIN] = 1
if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(f.Fd()), syscall.TCSETS, uintptr(unsafe.Pointer(&termios))); err != 0 {
return err
}
return nil
}
func OpenSerial(device string, baud uint) (s *serial, err error) {
myBaud := getBaud(baud)
if myBaud == 0 {
err = errInvalidBaud
return
}
fd, err := syscall.Open(
device,
os.O_RDWR|syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_NDELAY|syscall.O_NONBLOCK,
0666)
if err != nil {
return
}
defer func() {
if err != nil {
syscall.Close(fd)
}
}()
term := syscall.Termios{}
if err = sys.Ioctl(uintptr(fd), syscall.TCGETS, uintptr(unsafe.Pointer(&term))); err != nil {
return
}
term.Ispeed = myBaud
term.Ospeed = myBaud
term.Cflag |= (syscall.CLOCAL | syscall.CREAD)
term.Cflag = uint32(int32(term.Cflag) & ^syscall.PARENB & ^syscall.CSTOPB & ^syscall.CSIZE)
term.Cflag |= syscall.CS8
term.Lflag = uint32(int32(term.Lflag) & ^(syscall.ICANON | syscall.ECHO | syscall.ECHOE | syscall.ISIG))
term.Oflag = uint32(int32(term.Oflag) & ^syscall.OPOST)
term.Cc[syscall.VMIN] = 0
term.Cc[syscall.VTIME] = 100
if err = sys.Ioctl(uintptr(fd), syscall.TCSETS, uintptr(unsafe.Pointer(&term))); err != nil {
return
}
status := 0
if err = sys.Ioctl(uintptr(fd), syscall.TIOCMGET, uintptr(unsafe.Pointer(&status))); err != nil {
return
}
status |= syscall.TIOCM_DTR | syscall.TIOCM_RTS
if err = sys.Ioctl(uintptr(fd), syscall.TIOCMSET, uintptr(unsafe.Pointer(&status))); err != nil {
return
}
s = &serial{uintptr(fd)}
runtime.SetFinalizer(s, func(this *serial) {
this.Close()
})
return
}
func setTermSettingsBaudrate(speed int, settings *syscall.Termios) error {
baudrate, ok := baudrateMap[speed]
if !ok {
return &PortError{code: InvalidSpeed}
}
// revert old baudrate
var BAUDMASK uint
for _, rate := range baudrateMap {
BAUDMASK |= rate
}
settings.Cflag &= ^termiosMask(BAUDMASK)
// set new baudrate
settings.Cflag |= termiosMask(baudrate)
settings.Ispeed = termiosMask(baudrate)
settings.Ospeed = termiosMask(baudrate)
return nil
}
func setTermSettingsBaudrate(speed int, settings *syscall.Termios) error {
baudrate, ok := baudrateMap[speed]
if !ok {
return &SerialPortError{code: ERROR_INVALID_PORT_SPEED}
}
// revert old baudrate
BAUDMASK := 0
for _, rate := range baudrateMap {
BAUDMASK |= rate
}
settings.Cflag &= ^termiosMask(BAUDMASK)
// set new baudrate
settings.Cflag |= termiosMask(baudrate)
settings.Ispeed = termiosMask(baudrate)
settings.Ospeed = termiosMask(baudrate)
return nil
}
// Open a connection with a read timeout.
func (connection *Connection) Open(timeout uint8) error {
var err error
// The serial port is basically a file we are writing to and reading from.
// O_RDWR allows the program to read and write the file.
// O_NOCTTY prevents the device from controlling the terminal.
// O_NONBLOCK prevents the system from blocking for a long time.
connection.f, err = os.OpenFile(connection.Port,
syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_NONBLOCK, 0666)
if err != nil {
return err
}
// Close the file on error occurrence.
defer func() {
if err != nil && connection.f != nil {
connection.f.Close()
}
}()
// Create a plain termios, which allows the program to execute
// input/output operations.
termios := syscall.Termios{}
// Setup the baud rate in the termios structure.
baudrate := baudrates[connection.Baud]
termios.Cflag |= baudrate
termios.Ispeed = baudrate
termios.Ospeed = baudrate
// Setup stop bits in the termios structure.
switch connection.StopBit {
case StopBit1:
termios.Cflag &^= syscall.CSTOPB // CSTOPB = 0x40
case StopBit2:
termios.Cflag |= syscall.CSTOPB
default:
return errStopBit
}
// Setup data bits in the termios structure.
databit := databits[connection.DataBit]
termios.Cflag |= databit
// Setup parity in the termios structure.
switch connection.Parity {
case ParityNone:
termios.Cflag &^= syscall.PARENB // PARENB = 0x100
case ParityEven:
termios.Cflag |= syscall.PARENB
case ParityOdd:
termios.Cflag |= syscall.PARENB
termios.Cflag |= syscall.PARODD // PARODD = 0x200
default:
return errParity
}
// // set blocking / non-blocking read
vmin := uint8(0)
if timeout == 0 {
vmin = 1
}
// Attach min bytes and timeout to the termios structure.
termios.Cc = [32]uint8{
syscall.VMIN: vmin, // min bytes per transfer
syscall.VTIME: timeout, // actual read timeout in deciseconds
}
// Execute IOCTL with the modified termios structure to apply the changes.
if _, _, errno := syscall.Syscall6(
// device-specific input/output operations
syscall.SYS_IOCTL,
// open file descriptor
uintptr(connection.f.Fd()),
// a request code number to set the current serial port settings
uintptr(syscall.TCSETS),
//TODO: it looks like syscall.TCSETS is not available under
// freebsd and darwin. Is this a bug?
uintptr(unsafe.Pointer(&termios)), // a pointer to the termios structure
0,
0,
0,
); errno != 0 {
return errno
}
connection.isOpen = true
return nil
}
