Neptune Apex Physical Interface

On the surface, Neptune Apex Aqua Controller appears to be using a standard USB cable to connect to various modules. As mentioned in Apex documentation, this is actually not a USB interface, but rather a different interface that uses USB cables and sockets. Collectively, the Neptune’s commercial name for the interface is AquaBus. At the physical layer, AquaBus is implemented using a standard CAN transceiver. Many Apex Classic modules are found to use MAX3059 transceiver. It is important to note that this is not a CAN controller, but rather a CAN transceiver connected to UART of a basic controller for the purpose of converting CANbus signal to be UART compatible. The rest of the protocol is handled by a controller based on standard UART communication.

Aquabus CAN Transceiver Schematics:

Note that in this configuration specific to MAX3059 and Apex, the TERM pin on MAX3059 must be driven HIGH and the RS pin - LOW.

In addition to CAN related pins, Apex also provides 12V power over the remaining two pins.

Apex AquaBus Port Pinout:

In this configuration, you can use the 12v power supplied by Aquabus to power small electronic components, such as Arduino.