Remote ATU (variable coil) v 1.0       

Below project is all about situations in HAM radio, when requirements such as "remote control of ATU", "remote control of PA", "antenna remote tuning automation" and "additional management and monitoring for ATU and PA" are in place. If this is what you are looking for, then, fortunately, explanations "why" (those above may ever needed) are not nesessary and this project may give you some ideas.

Generic diagram:

ATU box is mounted on mast (attaced directly to antenna input).
ATU controlled by custom application, called ATUconnet, which is running on same PC with ESDR2/3. In background ATUconnet and Remote ATU utilises power of MQTT (which also runs in background on same PC) and TCI to MQTT Gateway .
Currently the only media used is WiFi; later we have plans to add CAN.

   - Automated or manual tuning.
   - ATU type presets and Antenna presets
   - 0.01W -500W tuning power.
   - Step values for ATU's L, C1 and C2 motors monitoring.
   - Actual values for L (in uH) and C1/C2 (in pF) monitoring.
   - ATU status display (i.e. “Ready”, “Tuned”, etc).
   - 5-12V (control) and 19-20V (step motors).

1. P-140 variable coil
2. Two variable capacitors 25-1000 pF
3. Espressif ESP32-DevKit - 2 pieces

Any compatible ESP32-DevKit can be used, just look around Ebay to find one you like.
4. A4988 Stepper Motor Driver - 3 pieces
5. Nema 17 Step Motor - 3 pieces
6. TCST2103 Photo-interrupter - 3 pieces
7. Tandem-Match/SWR-sensor

Software sources and binaries can be found at Github

ATUconnect application is the operational software, defined to run on same PC with ESDR2/3. It is integrated with SunSDR/ESDR via TCI and provides core user functions, i.e. ATU profiling, Antenna's profiling, ATU initialisation and ATU operations (tuning). Current SW version supports single ATU in TX/TX mode. In future versions the second ATU (primarily dedicated to RX mode) will be suported.
Latest UI consist of two Tabs - Dashboard and Setup:

Typical nessessary setup would include MQTT:

ATU profile:

and Antenna profile:

At glance - the combination of user-selectable starting tuning C1/C2/L values, starting step size and direction and selection of particular tuning algorithm (L first or C first) - provide quite powerfull mechanism to tune wide range of antennas.

ATUconnect is Qt.6 based cross-platform application.
Current version for macOS can be found here (important - tested on 10.15.7).

Please note that this software is currently under code cleanup and optimisation, hence the acceess to code is for development team only. Additionally we are working on feature enhancements: adding new features to allow granular control of the 8x8x8 remote ATU and provide more flexibility in tuning "unknown" DXpedition's antennas.

VK6NX overall concept, physical construct, initial programming, testing - and using :)
VK3FDMI SW concept, programming, customisation and optimisation.

Warm thanks to Dmitry RV9CX and Serge RA9DM for their support and suggestions.