I'd like to share with you my work around my Celestron Advanced GT mount and its Nexstar hand controller.
This is on old one with firmware version 4.21.
I simply heard communication between my laptop and the Nexstar by playing the man in the middle. I used all buttons on the controller, NexRemote software and PEC software and here is the final result, a spreadsheet.
I'm not a programmer, and I will take ages to modifiy the actual driver but it will be great to add new features to Celestron driver.
Of course, I will be glad to help for it.
Linux Mint 19 Cinnamon using PPA for latest KStars-bleeding and INDI
Raspberry Pi 3 B+ with StellarMate
Atik 314E - ASI120M - CG5 with Celestron C9.25
I have a Celestron CGE so if anything you discover can spill over and enhance the experience between INDI/EKOS/KSTARS with my celestron mount will be greatly appreciated.
Also appreciate the efforts of everyone here because some of us (namely myself) have no experience in coding (tried to get into it but my talents are limited), but we are willing testers of any developments that devs here would like us to confirm