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The gateway
One box running the Frigomar firmware, product ID 010010019. It is built for two hardware generations — CAN/Modbus and CAN/Serial v2 — and they install the same way. See The hardware for the box itself.
One gateway serves up to four Frigomar units: four serial channels, one unit on each, four MUXEN HVAC devices. Nothing shares a channel.
On the Frigomar side
| A Frigomar unit with its Modbus panel | the machine keeps its own controller and its own protections. The gateway reads the panel registers and writes two of them |
| The unit's Modbus address | the gateway does not search the line. It talks to one address per channel, the one written in RemoteAddr (default 1) |
| An RS-485 pair per unit | two wires and a common ground, back to one of the four serial connectors |
The air conditioner must be installed, commissioned and working before the gateway is fitted. The gateway drives a link; it does not set up an air conditioner.
Wiring
| Connector | Goes to | Link |
|---|---|---|
| CAN | the boat's MUXEN bus | 500 kbit/s |
| Serial 1 | Frigomar unit 1 | RS-485, Modbus RTU, 9600 baud, 8N1 |
| Serial 2 | Frigomar unit 2 | idem |
| Serial 3 | Frigomar unit 3 | idem |
| Serial 4 | Frigomar unit 4 | idem |
9600 baud, 8 data bits, no parity, 1 stop bit is fixed by the firmware. There is no parameter for it, on either side of the box. The Frigomar panel must be set to those values.
All four channels are driven as 2-wire half-duplex RS-485, and the firmware switches the box's own line termination on at every start. That is not configurable: the gateway is always terminated at its end. Terminate the other end at the unit, following Frigomar's instructions, and nowhere in between.
Channels are wired in any order — nothing forces unit 1 onto serial 1 — but the channel decides which MUXEN device the unit appears as, so write down which cabin is on which connector before closing the box. See Commissioning.
The MUXEN bus is an ordinary 120 Ω CAN bus: two wires and a common ground, one 120 Ω termination at each physical end and nowhere else. The gateway is terminated only if it happens to be at the end of a segment.
The serial channels and the MUXEN bus stay electrically separate. Nothing crosses from one to the other except the readings this firmware publishes and the commands it deliberately writes.
The box's own inputs and outputs
Independent of the air-conditioning function, this firmware also publishes a small generic I/O device:
| Relay output | 1, commanded from the MUXEN bus |
| Analog input | 1, published in millivolts |
Use it for whatever the installation needs — a temperature sender, a relay driving a valve. It ships not addressed and stays silent until it is given an instance number of its own and EnGenIo is set to 1. See Reference.