ROSMicroPy

ROS Type Support in Micropython

ROS Types in Micropython are defined at runtime using a 2 step process.

* .msg files -> converted to -> Python object

* Python object -> a ROSMicroPy type support instruction list

MicroROS RTIDL is a project that will automate the conversion from .msg files to Python object. This code can run on the device or a computer then upload the Python objects to the device.

Python object can be hand crafted also.

An example of this schema is here Geometry:Twist

class Twist():
    
    dataMap = {
        "message_name": "Twist",
        "message_namespace": "geometry_msgs::msg",
        "components": [
            {
                "name": "linear",
                "type": "Vector3",
                "components": [
                    {
                        "name": "x",
                        "type": "float64"
                    },
                    {
                        "name": "y",
                        "type": "float64"
                    },
                    {
                        "name": "z",
                        "type": "float64"
                    }
                ]
            },
            {
                "name": "angular",
                "type": "Vector3",
                "components": [
                    {
                        "name": "x",
                        "type": "float64"
                    },
                    {
                        "name": "y",
                        "type": "float64"
                    },
                    {
                        "name": "z",
                        "type": "float64"
                    }
                ]
            }
        ]
    }

The python object can be registered with the system, then the typeSupport object can be used to

typeTwist = registerDataType(Twist.dataMap)

#
# dumpDataType is used to output the instruction list for the Python Object
# This is used for Diagnostic purposes and can be deleted.
#
dumpDataType(typeTwist)

print("Registering Event Publishers\r\n")
pubCmdVel = registerROSPublisher("turtle1/cmd_vel", typeTwist)

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