FAQ: How to Change the Publishing Rates of Topics?

OEM7 Specific Topics

Most OEM7 specific topics (such as /novatel/oem7/bestpos) are generally driven by a single log as defined in config/std_init_commands.yaml.

Most published logs are either asynchronous (published when available, indicated by a ONNEW or ONCHANGED trigger) or synchronous (published at a periodic rate, indicated by a ONTIME trigger). For more information about the LOG command, see here: https://docs.novatel.com/OEM7/Content/Commands/LOG.htm The rate of the asynchronous logs can generally not be changed. The rate of synchronous logs can often be changed. For example config/std_init_commands.yaml calls:

- "LOG BESTPOSB ONTIME 0.1"

If you want /novatel/oem7/bestpos at a higher/lower rate you can modify the set frequency in config/std_init_commands.yaml. For example, change the command to below to have BESTPOS log at 20Hz instead:

- "LOG BESTPOSB ONTIME 0.05"

Warning

Each log will have a max rate that it can be logged at. Depending on the receiver model, most non-SPAN logs will generally be limited to either a maximum of 20Hz or 100Hz.

Warning

Increasing the logging rate may negatively impact the CPU usage of the receiver. If increasing the logging rate, other logs may need to be reduced in rate or stopped.

ROS Standard Topics

The ROS standard topics publishing is driven by various NovAtel logs with a single log often being the driving source. To increase the rate of these topics you will need to identify the log that drives the topic rate. This can be identified in ROS2 Topic Mapping

Once the command the drives the topic is known, you can then modify config/std_init_commands.yaml to increase the rate of that log.

CPT7 IMU Data Rate

By default, the CPT7 and CPT7700 are configured for a 100Hz raw IMU data rate.

This rate can generally be changed to 400Hz if required. Information about that can be found here.

Warning

Increasing the logging rate may negatively impact the CPU usage of the receiver. Closely monitor the CPU usage if increasing the IMU rate.