RFD900: Delays between Mission Planner and Drone

Hello community

We have a problem with the time delay between Mission Planner via RFD900 (or RFD868 in Europe) and our drone (PixHawk). For example, we want to switch from “Guided” to “Loiter”.

If we connect our laptop with Ardupilot Mission Planner to the drone via HereLink, then we have no time delay between switching a flight mode on the drone and displaying it in the Mission Planner. Switching of the flight mode on Mission Planner, acoustic signal of the drone (Pixhawk) and display of the new flight mode with white letters on Mission Planner occur quasi simultaneously.

However, when we connect the laptop to the drone via RDF900, the following happens:

With switching to another flight mode, the drone’s acoustic signal sounds quasi-simultaneously. One to two seconds (can be longer) later, the new flight state is displayed in red letters by the Mission Planner. We assume that this is to indicate the request for a new flight state. Then another one to two seconds later (can take longer) only the new/current flight state is displayed in white letters by the Mission Planner. We assume that this is the confirmation for the new flight state.

We interpret the behavior as MavLink messages are transmitted to the drone without delay, but MavLink messages to the Mission Planner are displayed by the Mission Planner with a significant delay.

We are surprised by the behavior of the Mission Planner. We would feel it more logical, if with the change of the flight state on the Mission Planner also the new flight state of the drone would be displayed immediately with red font and later, when the acknowledgement was received from the drone, the font changes from red to white.

Now for our questions:

  1. is this a bug in the Mission Plannersoftware?
  2. why or where do the delays in the display occur?

Does anyone have similar experiences or an idea how to improve the behavior?

And last but not least: We are using Mission Planner 1.3.80 on Windows 10

Mode change is displayed as soon as it is known to MP red indicates it was recently changed.

Thank you for the information.
I understand that correctly: The red and white display of the new flight state come only after the drone report the new flight state back to Mission Planner!