My DIY HUI DAW Controller

[bjosephs]

Should not, but you may check. I say few mm but thinking less, at 9bit a step is 1/5mm
What is the offset monitored from DAW (midi) value VS actual ADC value (midi converted) when fader is (miss)repositioned ?

In terms of dB, any given distance will be a fraction of a dB near unity and several dB on the low end of range. That’s what I’m referring to.

Did you implement some dead band at top and bottom ?

Nope. Going to -infinity works fine and jitter at the top of scale, where the value would bounce between +9.9 and +10dB, was solved with some rounding up. Basically the value +9.9dB is afforded half the range of other nearby dB values. In practice it’s not noticeable.

If not already, you probably need a scale map, because servo and ADC will probably never see 0.000V at bottom on 5.000V at top, if it's the values you expect to send 0x0000 and 0xFFFF, which can also be a reason for offset between DAW midi value and ADC feed back.

I didn’t need this. Probably because I’m using the external reference on my ADC. It will account for fluctuations. The actual read values off the slider are consistently 0 to 1023.

IIRC there is some DAW/controller that offer a flip to go in relative mode.
Whatever the fader position is, it flip mid travel, and you have +/- xdB from there.
Could be a nice feature, I was not able to implement it, as my fader pass audio I need an absolute and precise tracking between DAW value and fader real attenuation.

I recall playing with this but dropping it. I don’t think HUI supported “flip” natively. I tried to implement my own and was able to easily have the encoders trim the faders, but going the other way, V pots can only accept incremental values so there’s no way to reposition the faders off them.

Instead I built a pretty decent midi map into the faders and encoders. My DAW can learn CC messages and communicate bidirectionally. So, in midi mode I can, say, have the encoders alter an EQ frequency and the faders the +/- level of the band. It worked better than I thought it would.

Now that you have me thinking abut it I maybe add back in the ability to use the encoders for small fader level moves. I have some extra button space in the master section.

 

[zamproject]

Nope. Going to -infinity works fine and jitter at the top of scale, where the value would bounce between +9.9 and +10dB, was solved with some rounding up. Basically the value +9.9dB is afforded half the range of other nearby dB values. In practice it’s not noticeable.

Dead band also offer a safer hardware handle, to avoid any motor stall condition at full top or bottom if fader servo track/ADC can't send extreme value for any reason (like small voltage drop at the end of Vref wire string)
One mm at top and bottom is enough (98mm effective fader travel)

 

[bjosephs]

Dead band also offer a safer hardware handle, to avoid any motor stall condition at full top or bottom if fader servo track/ADC can't send extreme value for any reason (like small voltage drop at the end of Vref wire string)
One mm at top and bottom is enough (98mm effective fader travel)

Well that is 100% true. Though I will say that when you are only a few bits away from the target value the PID output constants are so low it might be impossible to drive the motor to a damaging level. Assuming the integral term is capped or reset periodically. I’ll put it on the list of things to review/change when I’m back on to software stuff. Thanks.

 

[bjosephs]

Ran into some trouble today. While soldering my signal LEDs I noticed some of the buttons were crooked or at different heights. As noted above I am using mezzanine headers with a controlled space but it seems that with enough (and sometimes not very much) pressure the plastic material that sets the gap distance will slide - not good. After reviewing options and thinking about how to control the gap I decided to canibalize the spacer material from extra headers and stack them up. I don’t like the height that three spacers gets me but 4 may be too much, so I’ll sleep on it.

Also please not that in one of the pictures below the contacts look blackened. It’s just a photo artifact they are still shiny gold.

 

[zamproject]

Though I will say that when you are only a few bits away from the target value the PID output constants are so low it might be impossible to drive the motor to a damaging level.

It's hard to blow a motor for sure, but it can unnecessary stress the belt on long term, and the driver (h-bridge ?) may keep an unrelaxed state that seek unnecessary current consumption.
At soft side on my system I add a script that hardware bypass (via a fet switch which first function is to hold the PID/motor driver when touch is activated) that deactivate the motor after 5 sec if not moved, this save me tens of mA for 16 faders in static position when all PID still to push a little.
The driver wake up instantly on incoming midi message (pitchbend in my use case) or after fader being manually moved and touch cap released.