updated readme

README.md

@@ -304,6 +304,22 @@ User can set the camera name and camera namespace, to distinguish between camera
   - This param also depends on **publish_tf** param
     - If **publish_tf:=false**, then no TFs will be published, even if **tf_publish_rate** is >0.0 Hz
     - If **publish_tf:=true** and **tf_publish_rate** set to >0.0 Hz, then dynamic TFs will be published at the specified rate
+- **unite_imu_method**:
+  - For the D400 cameras with built in IMU components, below 2 unrelated streams (each with it's own frequency) will be created:
+    - *gyro* - which shows angular velocity 
+    - *accel* - which shows linear acceleration. 
+  - Both streams will publish data to its corresponding topics:
+    - '/camera/camera/gyro/sample' & '/camera/camera/accel/sample'
+    - Though both topics are of same message type 'sensor_msgs::Imu', only their relevant fields are filled out.
+  - A new topic called **imu** will be created, when both *accel* and *gyro* streams are enabled and the param *unite_imu_method* set to > 0.
+    - Data from both accel and gyro are combined and published to this topic
+    - All the fields of the Imu message are filled out.
+    - It will be published at the rate of the gyro.
+  - `unite_imu_method` param supports below values:
+    - 0 -> **none**: no imu topic
+    - 1 -> **copy**: Every gyro message will be attached by the last accel message.
+    - 2 -> **linear_interpolation**: Every gyro message will be attached by an accel message which is interpolated to gyro's timestamp.
+  - Note: When the param *unite_imu_method* is dynamically updated, re-enable either gyro or accel stream for the change to take effect.
 
 #### Parameters that cannot be changed in runtime:
 - **serial_no**:
@@ -339,18 +355,6 @@ User can set the camera name and camera namespace, to distinguish between camera
   - For example: `initial_reset:=true`
 - **base_frame_id**: defines the frame_id all static transformations refers to.
 - **odom_frame_id**: defines the origin coordinate system in ROS convention (X-Forward, Y-Left, Z-Up). pose topic defines the pose relative to that system.
-
-- **unite_imu_method**:
-  - D400 cameras have built in IMU components which produce 2 unrelated streams, each with it's own frequency: 
-    - *gyro* - which shows angular velocity 
-    - *accel* which shows linear acceleration. 
-  - By default, 2 corresponding topics are available, each with only the relevant fields of the message sensor_msgs::Imu are filled out.
-  - Setting *unite_imu_method* creates a new topic, *imu*, that replaces the default *gyro* and *accel* topics.
-    - The *imu* topic is published at the rate of the gyro.
-    - All the fields of the Imu message under the *imu* topic are filled out. 
-  - `unite_imu_method` parameter supported values are [0-2] meaning:  [0 -> None, 1 -> Copy, 2 -> Linear_ interpolation] when:
-    - **linear_interpolation**: Every gyro message is attached by the an accel message interpolated to the gyro's timestamp.
-    - **copy**: Every gyro message is attached by the last accel message.
 - **clip_distance**:
   - Remove from the depth image all values above a given value (meters). Disable by giving negative value (default)
   - For example: `clip_distance:=1.5`

realsense2_camera/src/parameters.cpp

@@ -135,6 +135,8 @@ void BaseRealSenseNode::setDynamicParams()
                             [this](const rclcpp::Parameter& parameter)
                             {
                                 _imu_sync_method = imu_sync_method(parameter.get_value<int>());
+                                ROS_WARN("For the 'unite_imu_method' param update to take effect, "
+                                         "re-enable either gyro or accel stream.");
                             }, crnt_descriptor);
     _parameters_names.push_back(param_name);
 }