cras_msgs

Common ROS messages used by Center for Robotics and Autonomous Systems (CRAS) at Faculty of Electrical Engineering of Czech Technical University in Prague.

Parts of this package were used by team CTU-CRAS-Norlab in DARPA Subterranean Challenge.

Message Types

Heartbeat

Heartbeat messages can be sent by sensor drivers to allow easy diagnostics of publishing rate without the need to subscribe their possibly very large sensor messages.

The following naming convention should be used. If the sensor topic is TOPIC, the corresponding heartbeat messages should be published to TOPIC/heartbeat. If this convention is followed, diagnostic tools can automatically assign the heartbeats to the correct base topics.

Brightness, BrightnessStamped, SetBrightness

Brightness of e.g. a dimmable light with values ranging from 0.0 (dark) to 1.0 (full brightness).

ColorRGBAStamped, SetColor

Color of e.g. a color light or observed object.

ElectricCurrent, ElectricCurrentMeasurement, ElectricCurrentStamped

Representation of electric current measurements and values.

Power, PowerMeasurement, PowerStamped

Representation of electrical or mechanical power measurements and values.

PowerSwitchState, PowerSwitchStateStamped

State of an electric power switch (relay, transistor, FET…).

Voltage, VoltageMeasurement, VoltageStamped

Representation of voltage measurements and values.

C++ Helper - Pool-Allocated Sensor Messages

Header pool_allocated_sensor_msgs.h contains several defines of alternative message types to sensor_msgs types, which use a shared pool allocator for the dynamic-sized data they contain (strings and vectors). If you allocate a lot of messages of small to medium size, this could help decrease the load created by frequent memory allocations. However, for large messages (like 3D lidar pointclouds), the effect is questionable.

How to Use It

Just include the header and use e.g. sensor_msgs::ImagePoolAllocated where you would normally type sensor_msgs::Image. That’s it.

Warning

Publishers and subscribers using the pool-allocated type are incompatible with those using the default allocator. Therefore, if there is a mismatch of allocators between the publisher and subscriber, a serialization and deserialization step is performed to “convert” the message to the different allocator. This can be very costly and would usually hinder all the benefits gained by using the memory pool. It is therefore needed to have a very good idea about who the subscribers will be and how will they subscribe.