fix(dynamixel): store protocol_version and validate motor protocol

Persist protocol_version on DynamixelMotorsBus and add a MODEL_PROTOCOL
table so motors that don't match the requested protocol (e.g. an AX
motor on Protocol 2.0) are rejected at construction, mirroring Feetech.

src/lerobot/motors/dynamixel/dynamixel.py

@@ -33,6 +33,7 @@ from .tables import (
     MODEL_CONTROL_TABLE,
     MODEL_ENCODING_TABLE,
     MODEL_NUMBER_TABLE,
+    MODEL_PROTOCOL,
     MODEL_RESOLUTION,
 )
 
@@ -117,6 +118,8 @@ class DynamixelMotorsBus(SerialMotorsBus):
     ):
         require_package("dynamixel-sdk", extra="dynamixel", import_name="dynamixel_sdk")
         super().__init__(port, motors, calibration)
+        self.protocol_version = protocol_version
+        self._assert_same_protocol()
         self.port_handler = dxl.PortHandler(self.port)
         self.packet_handler = dxl.PacketHandler(protocol_version)
         print(f"Using protocol version {protocol_version}")
@@ -125,6 +128,14 @@ class DynamixelMotorsBus(SerialMotorsBus):
         self._comm_success = dxl.COMM_SUCCESS
         self._no_error = 0x00
 
+    def _assert_same_protocol(self) -> None:
+        if any(MODEL_PROTOCOL[model] != self.protocol_version for model in self.models):
+            raise ValueError(
+                f"Some motors are incompatible with protocol_version={self.protocol_version}. "
+                f"Expected per-model protocols: "
+                f"{ {model: MODEL_PROTOCOL[model] for model in self.models} }"
+            )
+
     def _assert_protocol_is_compatible(self, instruction_name: str) -> None:
         pass
 

src/lerobot/motors/dynamixel/tables.py

@@ -247,6 +247,20 @@ MODEL_BAUDRATE_TABLE = {
     "ax-12a": AX_SERIES_BAUDRATE_TABLE,
 }
 
+# {model: protocol_version}
+# AX series communicate over Protocol 1.0, X series over Protocol 2.0.
+MODEL_PROTOCOL = {
+    "x_series": 2,
+    "xl330-m077": 2,
+    "xl330-m288": 2,
+    "xl430-w250": 2,
+    "xm430-w350": 2,
+    "xm540-w270": 2,
+    "xc430-w150": 2,
+    "ax_series": 1,
+    "ax-12a": 1,
+}
+
 AVAILABLE_BAUDRATES = [
     9_600,
     19_200,