0 votes
asked by (253 points)

I've been working on a plugin which reads datarefs from x-plane and sends them through the ethernet to my home cockpit and then receives some data (like altimeter setting or transponder mode/id) from the cockpit and sends them back to x-plane. The plugin works fine, however it looks like some datarefs, which are described as writeable on http://www.xsquawkbox.net/xpsdk/docs/DataRefs.html, are not really writeable, or at least, writing a value to them has no effect.


- when transponder mode is changed, writing that value (0,1,2,3 or 4) to sim/cockpit/radios/transponder_mode or sim/cockpit2/radios/actuators/transponder_mode has no effect. Have to use XPLMCommandOnce(XPLMFindCommand("sim/transponder/transponder_on")) style command, which works ok.

- same thing with transponder ident button, sim/cockpit2/radios/indicators/transponder_id.

- writing, a float value to sim/cockpit/radios/transponder_code sets the transponder code without any problems, same with the altimeter setting value to sim/cockpit2/gauges/actuators/barometer_setting_in_hg_pilot does the trick.

Also, whenever I use the XPLMCommandOnce function, I can clearly hear a 'double click' sound, which is not there when writing to datarefs, only when executing commands with XPLMCommandOnce.


Would you, please, make those (and probably many more) 'writeable' datarefs really writeable? That would eliminate the need of using XPLMCommandOnce. Also, please advise on that click sound when executing commands with XPLMCommandOnce. It is really annoying.

Have tested my plugin on XP11.11 and 11.20vr1, both the same.

With regards to your hard and awesome work,


Please log in or register to answer this question.

Welcome to X-Plane Q&A, where you can ask support questions and get answers from members of the community.

This site is for X-Plane support questions only. Please search for existing answers before posting your question. Off-topic questions will be locked.

If you’re new, you’ll need to register before asking your first question.

If your question is answered, click on the check mark to select the best response.