Add processing units index page

Author: fjp

docs/processing_units/index.md

@@ -2,7 +2,9 @@
 
 Our robot consists of components which are connected as shown in the block diagram below:
 
-![Block Diagram Remo]({{ asset_dir }}/processing_units/block-diagram-remo.svg)
+[![Block Diagram Remo]][Block Diagram Remo]
+
+  [Block Diagram Remo]: {{ asset_dir }}/processing_units/block-diagram-remo.svg
 
 The Teensy 3.2 microcontroller board is connected to the encoder and optional IMU
 sensor as well as the motor driver actuator. It communicates to the Raspberry Pi 4 B via
@@ -15,4 +17,37 @@ connection diagram of the components:
 
 [![Remo Fritzing]][Remo Fritzing]
 
-  [Remo Fritzing]: /fritzing/remo_architecture.svg
+  [Remo Fritzing]: /fritzing/remo_architecture.svg
+
+
+## Overview of ROS nodes and topics for the Remo robot
+
+The following launch file will bring up the hardware nodes, load the robot description
+onto the parameter server, start `diff_drive_controller`, and begin to publish the
+transformations using `tf`. Run this launch file on the robot's SBC:
+
+```console
+roslaunch diffbot_bringup bringup.launch model:=remo
+```
+
+On the development PC, you can use the teleop node to steer the robot. To do this, run
+the following:
+
+```console
+roslaunch diffbot_bringup keyboard_teleop.launch
+```
+
+Issuing the rosnode list command shows the following list of started nodes:
+
+```console
+/diffbot/controller_spawner
+/diffbot/diffbot_base
+/diffbot/robot_state_publisher
+/diffbot/rosserial_base_controller
+/diffbot_teleop_keyboard
+/rosout
+```
+
+[![ROS nodes and topics of Remo]][ROS nodes and topics of Remo]
+
+  [ROS nodes and topics of Remo]: {{ asset_dir }}/processing_units/ros-nodes-remo.svg