Custom autopilot and GTN 750

[EGSC]

Since I know that Fsuipc can do such things, here is my problem.

PMDG Jetstream 41 is wonderful add-on, but the its own navigation system is rather dated, so I wanted to integrate Flight1 GTN 750 gps unit. Unfortunately, it does not work right away, even though Flight1 provided for such possibility and allowed autopilot steering from GTN while in Heading Hold mode, but it also does not work with JS-41.

However, what I found is that if I keep pressing continuously (several times per second) one specific button on JS41 autopilot panel , called "NAV", then aircraft will intercept and follow track from GTN. This NAV button is not default NAV1 hold button from FSX control assignments. Unfortunately, PMDG have not provided key assignments for their custom systems, unlike with other products.

Is there any way to identify/locate this button and set it for continuous engagement with the help of Fsuipc?

 

PS. I know that it is somehow possible to steer JS41 from custom gps unit, since this KLN-90B http://www.fsdeveloper.com/forum/threads/the-kln90b-for-fsx-prepar3d-in-beta.432845/ does the job while in alternative heading hold mode (this is what GTN750 allows too, but doesn't work right away).

 

Any help is really appreciated. Thank you!

 

Edited November 11, 2017 by EGSC

[Pete Dowson]

On 11/11/2017 at 11:07 PM, EGSC said:

However, what I found is that if I keep pressing continuously (several times per second) one specific button on JS41 autopilot panel , called "NAV", then aircraft will intercept and follow track from GTN. This NAV button is not default NAV1 hold button from FSX control assignments. Unfortunately, PMDG have not provided key assignments for their custom systems, unlike with other products.

Does the JS41 come with an SDK folder? If so, check the file with filetype .h, to see if they have custom controls like they do in the 737, 747 and 777 products.

Otherwise your recourse will be one of the following:

1. Use FSUIPC logging to see if any relevant Events are produced by that key (log events via Logging tab)
2. Log Lvars and see if an L:var can be used to control it There's an added FSUIPC control to list L:Vars and their values, and there's also a Lua plug-in in the Examples ZIP which will show them on screen in real time, as they change.
3. See if a mouse macro can be created for the button (not available in P3D4).

BTW there are a couple of threads about the JS41 in the User Contributions subforum above. Might be worth looking through those too.

Pete

 

[EGSC]

Thanks Pete for pointing me at those directions.

Mouse macros function didn't work with this panel.

I looked at JS41 LUA script made by guenseli user in 2011, but it didn't work, however I managed to identify some working parts and add infinite loop for continual engagement. I use "Lua Kill" control to terminate that loop when I no longer need aircraft to follow track to GTN. In the end it works perfectly now. 

 

Guide to couple JS41's autopilot and Flight1 GTN 750 (for those unfamiliar with LUA scripts / searching for ways to couple them).

1. Create a LUA file in Modules folder, e.g. PMDG_JS41_BTN.LUA

2. Add the following lines in it:

while 1 == 1 do
ipc.writeLvar("L:FdModeselNavSwitch", 1)
ipc.control(66587,278)
ipc.control(66587,8031)
ipc.sleep(200)
end

3. Open FSUIPC4.ini and add  under [LuaFiles] section (add this section if not present)
1=PMDG_JS41_BTN

4. Go to Sound\PMDG\J41 and rename or delete pmdgj41_rmu_knob.wav (since LUA script calls NAV button several times per second, you don't want to hear constant clicks). 

4. In Fsuipc, go to Key Presses tab, on the left press "SET", press some keyboard button, in "Controls sent keys pressed" below find "Lua PMDG_JS41_BTN", press confirm below (ensure this button doesn't conflict with FS key assignments. This button will engage steering from GTN.

5. Again, on the left press "SET", press some other keyboard button, in "Controls sent keys pressed" find "LuaKill PMDG_JS41_BTN", press confirm below. This button will disengage steering from GTN.

6. Go to F1GTN directory, F1GTNConfig.exe, find your aircraft with GTN, press "Configure GTN", select GTN unit on the top (one of the tabs), set "Autopilot" to "Heading hold" mode.

7. To engage steering from GTN, just engage JS41 autopilot with yaw damper, select some pitch mode as required and press Fsuipc button from step 4. There is no need to set CDI mode as "GPS" on GTN specifically, "VLOC" will work too.

4. Do not reference JS41' EHSI as it will not show CDI needle and waypoint info, refer to GTN instead. To disengage, press button from step 5 and use native roll mode as appropriate (HDG/NAV/APR/BC).

5. I noted that sometimes after such manipulations from external units (KLN-90B, GTN, etc.) native HDG mode won't engage properly. To resolve this, just recycle autopilot completely and all roll&pitch modes.

 

Thanks again Pete for your hint and your great tool!

Edited November 18, 2017 by EGSC