refactor: normalize data directory naming, and consolidate serial connection handling

src/pygui/backend/controllers/session_controller.py

@@ -309,9 +309,11 @@ class SessionController(QObject):
 
         # The new binary protocol sends payload of (sensorCount * 2) bytes
         # Each sensor is a big-endian 16-bit value (Sign-Magnitude).
+        expected_sensors = 80 if (family_code or "") == "X" else 244
+
         def parse_binary_frame(payload: bytes, seq: int) -> Frame:
             values = []
-            num_sensors = min(80, len(payload) // 2)
+            num_sensors = min(expected_sensors, len(payload) // 2)
             for i in range(num_sensors):
                 high_byte = payload[i * 2]
                 low_byte = payload[i * 2 + 1]
@@ -333,13 +335,9 @@ class SessionController(QObject):
         self._last = None
         self._last_raw_frame = None
 
-        try:
-            transport = pyserial.Serial(port, SerialPort.BAUDRATE, timeout=1)
-        except Exception as exc:
-            log.warning("Baud rate %d failed on %s, falling back to 115200: %s", SerialPort.BAUDRATE, port, exc)
-            transport = pyserial.Serial(port, 115200, timeout=1)
+        transport = SerialPort.open_port(port, timeout=1)
         # Send 'D2' command padded to 512 bytes to start the stream
-        cmd = b"D2" + (b"F" * 510)
+        cmd = b"D2" + SerialPort.COMMAND_PAD.encode()
         transport.write(cmd)
 
         def on_error(exc: Exception):