rosserial is a protocol for wrapping standard ROS serialized messages and multiplexing multiple topics and services over a character device such as a serial port or network socket.
MODM includes support for rosserial. See examples for an introduction.
On the host the rosserial Python bridge must be running, e.g.
rosrun rosserial_python serial_node.py _port:=/dev/ttyACM0 _baud:=1000000
The simplest example is the sub_pub example. It is made for a Nucleo board with an RGB Led (or three LEDs) connected to A0, A1, and A2 of the Arduino connector.
Compile the example and flash it to the board.
cd sub_pub
scons
scons program
The green LED on the board should toggle once per second. MODM uses rosserial to advertise a publisher (/button) and three subscribers (/led/red, /led/green, /led/blue).
On a Linux with ROS installed get a new ROS workspace:
mkdir -p modm_ws/src
cd modm_ws/src
catkin_init_workspace
git clone https://github.com/strongly-typed/modm_rosserial_demo.git
cd ..
catkin_make
source devel/setup.bash
And start the supplied launch file:
roslaunch modm_rosserial_demo modm_led_demo.launch
The led_demo.py-node subscribes to the /button topic from the Nucleo board and publishes new LED states to /led/[red, green, blue] topics.
The LEDs should toggle between red, green and blue with each button press. The expected console output should look like:
[INFO] [1509051381.245712]: ROS Serial Python Node
[INFO] [1509051381.266949]: Connecting to /dev/ttyACM0 at 1000000 baud
[INFO] [1509051381.297971]: /led_demo: MODM Rosserial Led Demo: Press the button to cycle red, green and blue LED.
[INFO] [1509051383.393886]: Note: publish buffer size is 512 bytes
[INFO] [1509051383.396080]: Setup publisher on /button [std_msgs/Bool]
[INFO] [1509051383.420355]: Note: subscribe buffer size is 512 bytes
[INFO] [1509051383.423184]: Setup subscriber on /led/red [std_msgs/Bool]
[INFO] [1509051383.448187]: Setup subscriber on /led/green [std_msgs/Bool]
[INFO] [1509051383.492618]: Setup subscriber on /led/blue [std_msgs/Bool]
[INFO] [1509051398.504384]: /led_demo: Button True
[INFO] [1509051398.507496]: /led_demo: Setting green
[INFO] [1509051398.683607]: /led_demo: Button False
[INFO] [1509051399.109279]: /led_demo: Button True
[INFO] [1509051399.112368]: /led_demo: Setting blue
This demonstrates the capability of modm to work with ROS as a data sink and data source.