That’s stilll a work in progress, but in another thread we have been working on reverse engineering the protocol used to control the Aqualisa “digital processor”
So far it looks like the 6 pin connector has 2 output data lines for LED status control, and 2 analogue inputs.
Hardware wise I think a ESP8266, using a tri-state GPIO connected to a weak voltage divider would give the 0-2.5-5v signal needed for Start/Stop and boost, the temperature can be controlled with a 0-5V signal so I was thinking a digital potentiometer or a PWM signal with a RC network for smoothing.
For feedback we should be able to read the states of the LED control lines.