Motorized faders with limited range

[illuminancephoto]

I'm trying my first controller with motorized faders (Behringer X-Touch Compact). I like to use absolute value controls with a limited range. For example by limiting the Exposure adjustment to +/- 3.00 in MIDI2LR Options, and assigning that to a controller that generates 0-60, with the MIDI2LR app configured to match, you get exposure varying from -3.00 to +3.00 in even 0.10 increments. Nice. As far as I can tell, though, when MIDI2LR sends the value back to the controller to position the fader, its interpreting the value as if the controller was using the full 0-127 range. So my fader may be positioned at 30/127 rather than 30/60, which means the controller and the parameter value are always out of sync, and I end up needing pickup mode with my motorized faders. Is there an easy way to make MIDI2LR send its position instruction scaled to a limited range?

[rsjaffe]

Yes, see https://github.com/rsjaffe/MIDI2LR/wiki/MIDI-Controller-Setup for how to set the controller range.

[illuminancephoto]

I understand how to limit the range in the app, and everything works as expected while adjusting the fader. The hardware is configured to generate 0-60, and the MIDI2LR app is configured to match, absolute values, min 0 and max 60. I get -3.00 to +3.00 with 0.10 increments when I move through the fader range, just like I want. Its when MIDI2LR positions the motorized fader that things get out of sync. Exposure of 0.00 should correspond to value 30 on my 0-60 limited control, and rather than being positioned half way as I'd like, it seems more like its being positioned at around 1/4 way through the range (-1.60 on my -3.00 to +3.00 scale). I'm guessing its getting positioned at 30/127, causing the parameter value and the physical fader position to be out of sync. If I set up the control to generate 35-95 instead of 0-60, and set the app to match, then I get the middle position to sync correctly, but the farther from 0.00 the parameter value is, the larger the sync error.

[rsjaffe]

Sounds like your fader is expecting 0-127 when setting a position. When you set the values to a limited range, MIDI2LR assumes that that is the range your controller uses. For example, if you set the CC control limits to 0-60, when MIDI2LR sees a 0 it assumes the controller is at 0% of its range, and when it sees a 60, it assumes the controller is at 100% of its range.

When data comes back from Lightroom, MIDI2LR uses that same range. So if a control in LR is at 0%, MIDI2LR will send a 0 to the MIDI controller, and when a control in LR is at 100%, MIDI2LR will send a 60 to the MIDI controller.

See

MIDI2LR/src/application/ControlsModel.cpp

Line 260 in 020d8d8

const auto newv {std::clamp(

for the details in how this is calculated.

[illuminancephoto]

Hmm. Hadn't considered that changing the output range to 0-60 with X-Touch Editor doesn't also change the input range to move the fader. That seems unfortunate but would definitely explain what's happening. I suppose that's a dead end for me. Use the full range or its never really going to work. Thanks for your time though. MIDI2LR is fantastic, and I appreciate your help!