improved logging

python_app/hardware_full/laser_control/protocol.py

@@ -1,11 +1,10 @@
-"""
-Communication protocol for laser control module.
+"""Communication protocol for the laser control module.
 
-Encodes commands to bytes and decodes device responses.
-Faithful re-implementation of the logic in device_commands.py,
-refactored into a clean, testable class-based API.
+Encodes commands to wire bytes, decodes device responses, and manages the
+serial port connection to the laser control board.
 """
 
+import logging
 import struct
 from typing import Optional
 from enum import IntEnum
@@ -38,6 +37,8 @@ from .exceptions import (
     ProtocolError,
 )
 
+logger = logging.getLogger(__name__)
+
 
 # Re-export enums so tests can import from protocol module
 class CommandCode(IntEnum):
@@ -77,11 +78,11 @@ def _int_to_hex4(value: int) -> str:
     return f"{value:04x}"
 
 
-def _flipfour(s: str) -> str:
-    """Swap two byte-pairs: 'aabb' → 'bbaa' (little-endian word)."""
-    if len(s) != 4:
-        raise ValueError(f"Expected 4-char hex string, got '{s}'")
-    return s[2:4] + s[0:2]
+def _flipfour(hex_word: str) -> str:
+    """Swap the two byte-pairs of a 4-char hex word: 'aabb' -> 'bbaa' (little-endian)."""
+    if len(hex_word) != 4:
+        raise ValueError(f"Expected 4-char hex string, got '{hex_word}'")
+    return hex_word[2:4] + hex_word[0:2]
 
 
 def _xor_crc(words: list) -> str:
@@ -183,7 +184,7 @@ class Protocol:
     # ---- Connection management
 
     def connect(self) -> None:
-        """Open the serial port. Auto-detects if port is None."""
+        """Open the serial port. Auto-detects the device path when port is None."""
         port = self._port_name or self._detect_port()
         try:
             self._serial = serial.Serial(
@@ -192,13 +193,16 @@ class Protocol:
                 timeout=SERIAL_TIMEOUT_SEC,
             )
         except Exception as exc:
+            logger.error("Cannot open laser serial port '%s': %s", port, exc)
             raise CommunicationError(
                 f"Cannot connect to port '{port}': {exc}"
             ) from exc
+        logger.debug("Laser serial port opened: %s @ %d baud", port, BAUDRATE)
 
     def disconnect(self) -> None:
         """Close the serial port if open."""
         if self._serial and self._serial.is_open:
+            logger.debug("Closing laser serial port")
             self._serial.close()
 
     @property
@@ -241,13 +245,14 @@ class Protocol:
 
     @staticmethod
     def calculate_crc(data: bytes) -> int:
-        """
-        XOR CRC over all 16-bit words except the last two bytes (CRC field).
-        Mirrors the original CalculateCRC logic.
+        """Return the XOR CRC over all 16-bit words except word 0 and the CRC field.
+
+        The command-code word (word 0) is excluded, matching the firmware's CRC
+        expectation.
         """
         hex_str = data.hex()
         words = [hex_str[i:i+4] for i in range(0, len(hex_str), 4)]
-        # Skip word 0 (command code) per original firmware expectation
+        # Word 0 (command code) is excluded from the CRC.
         crc_words = words[1:]
         result = int(crc_words[0], 16)
         for w in crc_words[1:]:
@@ -342,9 +347,8 @@ class Protocol:
             case TaskType.CHANGE_CURRENT_LD2:
                 data += _flipfour(_int_to_hex4(current_ma_to_n(min_value)))      # Word 3
                 data += _flipfour(_int_to_hex4(current_ma_to_n(max_value)))      # Word 4
-                # Word 5: current step encoded like LD1 and like min/max (current_ma_to_n),
-                # NOT int(step*100) — the latter was a copy/paste from temperature scaling
-                # and produced a different wire value than LD1 for the same physical step.
+                # Word 5: current step uses the same current_ma_to_n scaling as
+                # min/max (and as LD1) so equal physical steps map to equal wire values.
                 data += _flipfour(_int_to_hex4(current_ma_to_n(step)))           # Word 5
                 data += _flipfour(_int_to_hex4(int(time_step * 100)))            # Word 6: Delta_Time_µs × 100
                 data += _flipfour(_int_to_hex4(temp_c_to_n(static_temp2)))       # Word 7