update readme

spot_controllers/README.md

@@ -2,6 +2,39 @@
 
 This is a ROS 2 package that provides custom ROS 2 controllers that can be used with [spot_ros2_control](../spot_ros2_control/).
 
-Currently, this package consists of a single generic controller: `spot_controllers/ForwardStateController`. This controller allows you to forward a set of commands over a set of interfaces. It is used with `spot_ros2_control` to forwad commands for position, velocity, and effort for all joints at the same time. 
+This package contains two controllers: `spot_controllers/ForwardStateController` and `spot_controllers/SpotJointController`.
+Example configurations for setting up this controllers can be found in [`spot_ros2_control/config`](../spot_ros2_control/config/).
 
-Example configurations for setting up this controller can be found in [`spot_ros2_control/config`](../spot_ros2_control/config/).
+## `ForwardStateController`
+
+This is a generic controller allows you to directly forward a set of commands over a set of interfaces.
+It builds on top of ROS 2 control's [`forward_command_controller`](https://github.com/ros-controls/ros2_controllers/tree/master/forward_command_controller).
+It is used with `spot_ros2_control` to forwad commands for position, velocity, and effort for all joints at the same time. 
+
+
+## `SpotJointController`
+
+This is a streaming controller specific to Spot's hardware interface, used to directly forward any subset of position, velocity, load, k_q_p, and k_qd_p over any subset of Spot's joints.
+It receives commands of type `spot_msgs/msg/JointCommand`, which is almost the same as a `sensor_msgs/msg/JointState` message but with extra fields for Spot's `k_q_p` and `k_qd_p` command interfaces.
+This controller claims all command interfaces of the robot on activation, but your `JointCommands` do not have to contain commands for all interfaces -- they can just contain a subset.
+The `name` field in this topic should contain the names of the joints you wish to control, and for each entry in `name`, you can fill one or more of the elements in `postition`, `velocity`, `effort`, `k_q_p`, or `k_qd_p`.
+Any interfaces that are not specified in this message will be left unchanged at their last commanded value.
+
+For example, to send one position command to one joint, the joint command would be formed such as:
+```
+name: ["joint_1"]
+postion: [1.0]
+velocity: []
+effort: []
+k_q_p: []
+k_qd_p: []
+```
+Or to control position, velocity, and k_qd_p of 3 different joints:
+```
+name: ["joint_1", "joint_2", "joint_3"]
+postion: [1.0, 2.0, 3.0]
+velocity: []
+effort: [4.0, 5.0, 6.0]
+k_q_p: []
+k_qd_p: [7.0, 8.0, 9.0]
+```

spot_controllers/include/spot_controllers/spot_joint_controller_parameters.yaml

@@ -4,13 +4,3 @@ spot_joint_controller:
     default_value: [],
     description: "Names of the joint to control",
   }
-  joint_prefix: {
-    type: string,
-    default_value: "",
-    description: "Optional prefix to apply to joint names"
-  }
-  interface_names: {
-    type: string_array,
-    default_value: [],
-    description: "Names of the interfaces to command",
-  }