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How To Get Calibrated Throttle Lever Position with A/T engaged


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Hi Pete

Is there any way to get the current calibrated throttle axis position while the auto-throttle is engaged (ie 0-1 rather than –4096 to +16384)? I can't see one in the documentation and the various offsets that support the throttle axis seem to report zero when the a/t is on. (I'm using a single throttle to control all engines).

I've written my own PFD and want to display my thrust lever's position next to the a/t setting in a spare corner somwhere. This will allow me to match my throttle lever to the a/t's current setting so that when I disengage the a/t there's no sudden drop or surge in power.

Do you know of any way to derive this info, or is there a new offset you could introduce to make the info available?

Thanks for any insights you can offer!

Ian

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Is there any way to get the current calibrated throttle axis position while the auto-throttle is engaged (ie 0-1 rather than –4096 to +16384)?

It's the same thing. Just take the 0-16384 and divide by 16384. You won't get -ve numbers with A/T engaged.

I can't see one in the documentation and the various offsets that support the throttle axis seem to report zero when the a/t is on.

That can't be true as a lot of motorised throttles read the value in order to position the throttle levers automatically. But there are separate read-outs for each engine still -- 088C for Engine 1, etc.

Regards

Pete

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Hi Pete, no luck I'm afraid. The results of testing various throttle offsets are as follows (don't forget, I'm using a single combined throttle):

088C (2 bytes) Returns the current throttle setting in FSX. It's unaffacted by throttle axis inputs when A/T is engaged.

089A (2 bytes) Always returns 0 when a/t is engaged

332E (2 bytes) Returns -16383 to +16383 and appears to be pre-calibration (documented as post-calibration, interestingly)

For my throttle's full range of movement it returns roughly -14,000 to +14,000 and if I manually adjust it to get a 0 to 1 range

it shows 0.5 to 0.95, so I can't really use it.

3330 (2 bytes) Always returns 0 when a/t is engaged

3AE8 (8 bytes) Returns the current throttle setting in FSX (post calibtation - 0 to 1). It's unaffacted by throttle axis inputs when A/T is engaged.

In an ideal world I need 332E to be the post-calibration value (0 to 1) so that I can pair it with 3AE8 on my display to get the comparison values I need.

Best as always,

Ian

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Hi Pete, no luck I'm afraid. The results of testing various throttle offsets are as follows (don't forget, I'm using a single combined throttle):

... 088C (2 bytes) Returns the current throttle setting in FSX. It's unaffacted by throttle axis inputs when A/T is engaged.

Correct. Sorry, I see I rather misread you as wanting the throttle value -- the one in use by the A/T. If you want the FSUIPC calibrated throttle axis input you use the values at 332E etc.

332E (2 bytes) Returns -16383 to +16383 and appears to be pre-calibration (documented as post-calibration, interestingly)

Hmm. I'm pretty sure the documentation is correct. FSUIPC will be calibrating whatever range your axis gives to the proper FSUIPC value -16k to +16k, as you are seeing.

For my throttle's full range of movement it returns roughly -14,000 to +14,000 and if I manually adjust it to get a 0 to 1 range it shows 0.5 to 0.95, so I can't really use it.

Er, that seems to contradict what you just said about the offset ranging from -16k to +16k?

In an ideal world I need 332E to be the post-calibration value (0 to 1)

It'll never be 0-1. If it's a -16k to +16k range you'd need to add 16k and divide by 32k.

If you want me to check anything further for you you'll need to give some more information, like:

1. Version of FS, version of FSUIPC

2. How are you assigning the axis

3. Whether you are setting the 310A bit to prevent the axis being sent to FS and interfering with the A/T.

That last is important. I've a feeling the operation is different depending on that setting -- those offsets never used to be updated at all unless the axis was disconnected.

Regards

Pete

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Hi Pete

It looks like 332E is what I need but it's definitely returning pre-calibration data. The initial range I listed (=/- 16k) was what I assumed to be the full range of acceptable values, the +/-14k range is what I'm actually seeing (which is my pre-calibration throttle axis range). Perhaps it's just a documentation error?

Anyway, I've thrown some rough and ready calibration code of my own into my PFD and I'm getting approximately what I need - certainly it appears to be close enough but if you ever have a spare moment it'd be nice to get the true post-calibration data from FSUIPC.

Thanks for your help,

Ian

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It looks like 332E is what I need but it's definitely returning pre-calibration data. The initial range I listed (=/- 16k) was what I assumed to be the full range of acceptable values, the +/-14k range is what I'm actually seeing (which is my pre-calibration throttle axis range). Perhaps it's just a documentation error?

Are you setting the bit in 310A?

Which version of FSUIPC?

I'm a bit confused by this, as the intention for those offsets was for use by "Fly-by-Wire" software applications to read the disconnected calibrated value and either pass them directly to the main throttle offsets and manipulate them (fly-by-wire-like) and then do so. They've been used like that for years. But I suspect you have to use the disconnection feature for them to work like that.

I still need information from you, as I asked, before I can check.

There's no rush -- I can't do any programming or debugging for a few days (re-building at present). Maybe next Wednesday or later.

Regards

Pete

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Hi Pete, appreciate you're busy with the build - no rush on this but I'll leave you with the info so you can mull it over if you get a chance next week.

OK, so I'm using v4.70b, built 15/4/11

The Axis assignment is being done via FSUIPC (none of my axiis are assigned via the FSX controls dialog). The throttle axis I'm using is assigned to 'Throttle' in the Axis Assignment tab and is calibrate on the Joystick Calibration Tab using page 1.

As for the offset values, I did a thorough test both with and without the axis 'de-activation' switches. During the tests I verified that the throttle was either still controlling the engines or having no effect as specified vai 310A. The results were:-

-----+------------------------------------+------------------------------------+
     |          310A = 0                  |          310A = xC8                |   
-----+--------------+---------------------+--------------+---------------------+
     | A/T Discon   |  A/T Engaged        | A/T Discon   | A/T Engaged         |
=====+==============+=====================+==============+=====================+
332E | -14k to +14k | -14k to +14k        | -14k to +14k | -14k to +14k        |
-----+--------------+---------------------+--------------+---------------------+
3330 | Always 0     | Always 0            | Always 0     | Always 0            |
-----+--------------+---------------------+--------------+---------------------+
088C | 0 to 16k     | Controlled by A/T   | 0 to 16k     | Controlled by A/T   |
     |              | Axis has no effect  |              | Axis has no effect  |
     |              | Appears to be 0-16k |              | Appears to be 0-16k |
-----+--------------+---------------------+--------------+---------------------+
089A | Always 0     | Always 0            | Always 0     | Always 0            |
-----+--------------+---------------------+--------------+---------------------+
3AE8 | 0 - 1.0      | Controlled by A/T   | 0 - 1.0      | Controlled by A/T   |
     |              | Axis has no effect  |              | Axis has no effect  | 
     |              | Appears to be 0-1.0 |              | Appears to be 0-1.0 |
-----+--------------+---------------------+--------------+---------------------+

From all these tests I think the documentation for 332A should say that it's pre-calibration not post which leaves us without a bona fide post-calibration but pre-FSX offset to read. Also, 310A definitely disconnects the axis from FSX but doesn't appear to alter the data that's read from any of these offsets. I guess third party apps and hardware deal with calibration it internally (?)

Anyway, I'll let you get back to the build! Thanks for your input, let's leave it till sometime next week...

Best

Ian

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Anyway, I'll let you get back to the build! Thanks for your input, let's leave it till sometime next week...

Thanks for the info. There's one other thought I had -- it may be that the calibrated values were only done for the 4 individual throttles -- I suspect this is what would be used by 99.9% of those needing this facility.

So, you could try assigning to Throttle 1 instead of just "throttle" and mapping to the others using the facilities there. Or assigning to throttle as now but mapping to all 4. To get the same non-reverse option you'd need to set the "NRZ" option too.

Let me know please.

Regards

Pete

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So, you could try assigning to Throttle 1 instead of just "throttle" and mapping to the others using the facilities there

Ta-da! That's got it, thanks Pete. With my axis mapped to Throttle 1, calibrated on page 3 of the Joystick Calibration tab (with no reverser zone) and mapped to throttles 2,3 and 4 I can get it's calibrated value from offset x3320, even with the A/T on. Exactly what I need so job done - thanks again!

Ian

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