diff --git a/ch-11/1-measuring-wheel-speeds/code.py b/ch-11/1-measuring-wheel-speeds/code.py
index fa7e5e7..5a55df4 100644
--- a/ch-11/1-measuring-wheel-speeds/code.py
+++ b/ch-11/1-measuring-wheel-speeds/code.py
@@ -14,7 +14,7 @@ async def motor_speed_loop():
     left_last = left_new
     right_speed = robot.ticks_to_m * (right_new - right_last) / Settings.time_interval
     right_last = right_new
-    robot.uart.write(f"{left_speed:.3f},{right_speed:.3f},0\n".encode())
+    robot.send_line(f"{left_speed:.2f},{right_speed:.2f},0")
 
 async def stop_motors_after(seconds):
   await asyncio.sleep(seconds)
@@ -28,21 +28,22 @@ async def command_handler():
         Settings.speed = float(command[1:])
       elif command.startswith("T"):
         Settings.time_interval = float(command[1:])
-      elif command == "O":
+      elif command == "G":
         robot.stop()
-      elif command.startswith("O"):
+      elif command.startswith("G"):
         await asyncio.sleep(5)
         asyncio.create_task(stop_motors_after(float(command[1:])))
         robot.set_left(Settings.speed)
         robot.set_right(Settings.speed)
       elif command.startswith("?"):
-        robot.uart.write(f"M{Settings.speed:.1f}\n".encode())
-        robot.uart.write(f"T{Settings.time_interval:.1f}\n".encode())
+        robot.send_line(f"M{Settings.speed:.1f}")
+        robot.send_line(f"T{Settings.time_interval:.1f}")
         await asyncio.sleep(3)
     await asyncio.sleep(0)
 
 try:
-  asyncio.create_task(motor_speed_loop())
+  motor_task = asyncio.create_task(motor_speed_loop())
   asyncio.run(command_handler())
 finally:
+  motor_task.cancel()
   robot.stop()
diff --git a/ch-11/1-measuring-wheel-speeds/robot.py b/ch-11/1-measuring-wheel-speeds/robot.py
index e529414..8905355 100755
--- a/ch-11/1-measuring-wheel-speeds/robot.py
+++ b/ch-11/1-measuring-wheel-speeds/robot.py
@@ -59,3 +59,6 @@ def set_left(speed):
 
 def set_right(speed):
     set_speed(right_motor, speed)
+
+def send_line(message):
+    uart.write(f"{message}\n".encode())