[dynamixel_general_hw] Explain write_read_interval more clearly

dynamixel_general_hw/README.md

@@ -324,7 +324,7 @@ Optional Arguments:
   robot_description_param (default "robot_description"): Name of robot_description parameter read by the nodes started by this launch file. If this is a relative name, its global name becomes (namespace)/(robot_description_param)
   rvizconfig (default "/home/pazeshun/catkin_ws/src/dynamixel-workbench/dynamixel_general_hw/config/sample_robot.rviz"): Configuration file for RViz
   set_robot_description (default "true"): Whether to set robot_description parameter at launching
-  write_read_interval (default "-1"): Minimal interval [sec] from writing Dynamixel to reading Dynamixel. -1 means fastest execution. You can increase this if you face reading error even when you decrease latency_timer as much as you can. Cf. https://forum.robotis.com/t/error-reading-position-value-after-write-position/6207
+  write_read_interval (default "-1"): Minimal interval [sec] from writing Dynamixel to reading Dynamixel. Non-positive value means that interval will be entirely determined by control_rate and how long reading and writing take. You can increase this if you face reading error even when you decrease latency_timer as much as you can. Cf. https://forum.robotis.com/t/error-reading-position-value-after-write-position/6207
 ```
 
 #### Minimal publishing topics

dynamixel_general_hw/launch/dynamixel_general_control.launch

@@ -38,7 +38,7 @@
   <arg name="publish_input_voltage" default="true"
        doc="Whether to publish Dynamixel actuator input voltage" />
   <arg name="write_read_interval" default="-1"
-       doc="Minimal interval [sec] from writing Dynamixel to reading Dynamixel. -1 means fastest execution. You can increase this if you face reading error even when you decrease latency_timer as much as you can. Cf. https://forum.robotis.com/t/error-reading-position-value-after-write-position/6207" />
+       doc="Minimal interval [sec] from writing Dynamixel to reading Dynamixel. Non-positive value means that interval will be entirely determined by control_rate and how long reading and writing take. You can increase this if you face reading error even when you decrease latency_timer as much as you can. Cf. https://forum.robotis.com/t/error-reading-position-value-after-write-position/6207" />
   <arg name="launch_rviz" default="false"
        doc="Whether to start RViz" />
   <arg name="rvizconfig" default="$(find dynamixel_general_hw)/config/sample_robot.rviz"