Rename es24n/ to modules/

Update sys.path reference in es24n_conf.py and all documentation
to reflect the new folder name.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/serial_port.py

@@ -0,0 +1,124 @@
+"""
+serial_port.py — Minimal 8N1 serial port using only the Python standard library.
+Replaces pyserial for TrueNAS environments where pip is unavailable.
+"""
+
+import fcntl
+import os
+import select
+import termios
+import time
+from typing import Optional
+
+
+class SerialPort:
+    BAUD_MAP = {
+        9600:   termios.B9600,
+        19200:  termios.B19200,
+        38400:  termios.B38400,
+        57600:  termios.B57600,
+        115200: termios.B115200,
+    }
+
+    def __init__(self, port: str, baudrate: int = 115200, timeout: float = 5.0):
+        self.port     = port
+        self.baudrate = baudrate
+        self.timeout  = timeout
+        self._fd: Optional[int] = None
+        self._saved_attrs       = None
+
+    # ── Open / close ──────────────────────────────────────────────────────────
+    def open(self):
+        try:
+            self._fd = os.open(self.port, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+        except OSError as e:
+            raise OSError(f"Cannot open {self.port}: {e}") from e
+
+        # Switch back to blocking mode now that O_NOCTTY is set
+        flags = fcntl.fcntl(self._fd, fcntl.F_GETFL)
+        fcntl.fcntl(self._fd, fcntl.F_SETFL, flags & ~os.O_NONBLOCK)
+
+        self._saved_attrs = termios.tcgetattr(self._fd)
+
+        # Raw 8N1: iflag, oflag, cflag, lflag, ispeed, ospeed, cc
+        attrs = list(termios.tcgetattr(self._fd))
+        baud  = self.BAUD_MAP.get(self.baudrate, termios.B115200)
+
+        attrs[0] = termios.IGNBRK                               # iflag
+        attrs[1] = 0                                             # oflag
+        attrs[2] = termios.CS8 | termios.CREAD | termios.CLOCAL # cflag
+        attrs[3] = 0                                             # lflag (raw)
+        attrs[4] = baud                                          # ispeed
+        attrs[5] = baud                                          # ospeed
+        attrs[6][termios.VMIN]  = 0
+        attrs[6][termios.VTIME] = min(int(self.timeout * 10), 255)
+
+        termios.tcsetattr(self._fd, termios.TCSANOW, attrs)
+        termios.tcflush(self._fd, termios.TCIOFLUSH)
+
+    def close(self):
+        if self._fd is not None:
+            try:
+                if self._saved_attrs:
+                    termios.tcsetattr(self._fd, termios.TCSADRAIN, self._saved_attrs)
+                os.close(self._fd)
+            except OSError:
+                pass
+            finally:
+                self._fd = None
+
+    @property
+    def is_open(self) -> bool:
+        return self._fd is not None
+
+    # ── Read / write ──────────────────────────────────────────────────────────
+    def write(self, data: bytes):
+        if self._fd is None:
+            raise OSError("Port is not open")
+        os.write(self._fd, data)
+
+    def read_chunk(self, size: int = 4096) -> bytes:
+        if self._fd is None:
+            raise OSError("Port is not open")
+        try:
+            return os.read(self._fd, size)
+        except OSError:
+            return b""
+
+    def read_until_quiet(self, quiet_period: float = 0.5) -> str:
+        """
+        Read until no new bytes arrive for `quiet_period` seconds,
+        or until `self.timeout` total seconds have elapsed.
+        """
+        output   = b""
+        deadline = time.monotonic() + self.timeout
+        last_rx  = time.monotonic()
+
+        while True:
+            now = time.monotonic()
+            if now >= deadline:
+                break
+            if output and (now - last_rx) >= quiet_period:
+                break
+
+            wait = min(deadline - now, quiet_period)
+            ready, _, _ = select.select([self._fd], [], [], wait)
+            if ready:
+                chunk = self.read_chunk()
+                if chunk:
+                    output  += chunk
+                    last_rx  = time.monotonic()
+
+        return output.decode("utf-8", errors="replace")
+
+    def send_line(self, cmd: str = "", delay: float = 0.3):
+        self.write((cmd + "\r\n").encode("utf-8"))
+        time.sleep(delay)
+
+    # ── Context manager ───────────────────────────────────────────────────────
+    def __enter__(self):
+        self.open()
+        return self
+
+    def __exit__(self, *_):
+        self.close()