Part 2: Electronics to control the mount
As mentioned before, I decided to build a controller based on OnStep project. OnStep is an open source project with all details freely available. OnStep controller connects to PC via USB and comes with ASCOM driver so the usual astro Windows software works out of the box. A mobile phone can be used as a hand controller via Bluetooth. OnStep also supports WiFi and can be connected to this way. I never used this option as there was no need for it.
One of the features that I am missing in my NEQ6 is that you can connect to it from multiple devices at the same time. I could just pause guiding in PHD (connected via USB) and move to a different object via SkySafari on my phone, connected by Bluetooth. Both devices (PC and mobile phone) can be connected at the same time... actually a 3rd device can be also used via WiFi.
To build electronics, I decided not to go the "Arduino way". I am not a big fan of Arduino, I think it is too expensive and way underpowered compared to alternatives. I already had a Tiva (Stellaris) Launchpad TM4C board which runs Arduino IDE clone (Energia) so I modified the OnStep code to run on it. My modifications have been accepted by the OnStep maintainer and OnStep now officially supports Launchpad TM4C boards. That is the beauty of open source
The Launchpad connects to PC via USB. For Bluetooth I used an industrial Bluetooth module Parani ESD200. This gives 100% reliable connection with a long range of 30m - I actually tested it to be much, much more (around 100m with direct line of sight).
The electronics has been placed in a plastic box. I have used IP67 rated (waterproof) connectors for everything.