I was given a Denford CNC machine that is in amazing condition.
It was controlled through a proprietary software that is no longer maintained. Instead of reverse engineering the serial protocol that interfaces to the old controller, I decided to make a new controller.
The new controller is based on GRBL and is a drop in replacement for the old one. It sits on the 93 way header and uses a cheap microcontroller board to run GRBL.
All inputs are protected with clamping diodes to protect against voltage spikes. Additionally there is an RC filter which debounces the switches and a buffer.
Because I don't have a computer near my CNC and I didn't want to make a USB cable to hook it up to my phone, I decided to add the option to use a Bluetooth transceiver with the board. This lets me connect to it using my phone and this works amazingly well. I do all the homing and Gcode streaming through an app called '''GRBL Controller'''. Everything work