diff --git a/lerobot/common/robot_devices/motors/dynamixel.py b/lerobot/common/robot_devices/motors/dynamixel.py
index 3cf0f50b..e7359a32 100644
--- a/lerobot/common/robot_devices/motors/dynamixel.py
+++ b/lerobot/common/robot_devices/motors/dynamixel.py
@@ -1,5 +1,7 @@
 import enum
+import sys
 import time
+import traceback
 from copy import deepcopy
 from pathlib import Path
 
@@ -278,8 +280,15 @@ class DynamixelMotorsBus:
         self.port_handler = PortHandler(self.port)
         self.packet_handler = PacketHandler(PROTOCOL_VERSION)
 
-        if not self.port_handler.openPort():
-            raise OSError(f"Failed to open port {self.port}")
+        try:
+            if not self.port_handler.openPort():
+                raise OSError(f"Failed to open port '{self.port}'.")
+        except Exception:
+            traceback.print_exc()
+            print(
+                "\nTry running `python lerobot/common/robot_devices/motors/dynamixel.py` to make sure you use the correct port."
+            )
+            sys.exit(1)
 
         self.port_handler.setBaudRate(BAUD_RATE)
         self.port_handler.setPacketTimeoutMillis(TIMEOUT_MS)
diff --git a/lerobot/common/robot_devices/robots/koch.py b/lerobot/common/robot_devices/robots/koch.py
index f80e6ccf..af86aeff 100644
--- a/lerobot/common/robot_devices/robots/koch.py
+++ b/lerobot/common/robot_devices/robots/koch.py
@@ -420,6 +420,7 @@ class KochRobot:
         if not record_data:
             return
 
+        # TODO(rcadene): Add velocity and other info
         # Read follower position
         follower_pos = {}
         for name in self.follower_arms:
diff --git a/lerobot/scripts/control_robot.py b/lerobot/scripts/control_robot.py
index 5398b999..ca0226b7 100644
--- a/lerobot/scripts/control_robot.py
+++ b/lerobot/scripts/control_robot.py
@@ -127,7 +127,7 @@ def log_control_info(robot, dt_s, episode_index=None, frame_index=None):
 
     def log_dt(shortname, dt_val_s):
         nonlocal log_items
-        log_items += [f"{shortname}:{dt_val_s * 1000:5.2f}={1/ dt_val_s:3.1f}hz"]
+        log_items += [f"{shortname}:{dt_val_s * 1000:5.2f} ({1/ dt_val_s:3.1f}hz)"]
 
     # total step time displayed in milliseconds and its frequency
     log_dt("dt", dt_s)
@@ -149,11 +149,7 @@ def log_control_info(robot, dt_s, episode_index=None, frame_index=None):
     for name in robot.cameras:
         key = f"read_camera_{name}_dt_s"
         if key in robot.logs:
-            log_dt("dtRcam", robot.logs[key])
-
-        key = f"async_read_camera_{name}_dt_s"
-        if key in robot.logs:
-            log_dt("dtARcam", robot.logs[key])
+            log_dt(f"dtR{name}", robot.logs[key])
 
     logging.info(" ".join(log_items))