The hardware

Three boards exist in this line. Two of them are generations of the same box; the third is the first board of the family and is no longer built.

	CAN/VE	CAN Serial/Modbus	CAN Serial/Modbus V2
Hardware ID	990010012	990010053	990010063
Tag in the image name	—	-MODBUS	-SERIAL-V2
Software version series	5.x	5.x	6.x
Microcontroller	STM32L431, 80 MHz	STM32L431, 80 MHz	STM32U575, 160 MHz
MUXEN CAN port	1, fixed at 500 kbit/s	same	same
Serial channels	4, VE.Direct levels, fixed	4, line drivers set by firmware	4, line drivers set by firmware
Relay output	1	1	1
Analog input	1	1	1
Switched sensor supply	no	no	yes
Signing key	its own	its own	its own
Still built	no	yes	yes

CAN/VE is the original board. Its four serial channels are wired for VE.Direct and nothing else: fixed levels, fixed direction, no termination control. One product was ever released on it — the VE.Direct gateway, 010010002. It is documented here because boxes are still in service, not because you can order one.

CAN Serial/Modbus is the same box with the serial front end made switchable. Same processor, same memory map, same CAN port, same relay and analog input. What changed is that each of the four channels now sits behind a line driver whose direction, duplex mode and line termination are set by the firmware — which is what lets one board carry both VE.Direct and Modbus RTU products.

CAN Serial/Modbus V2 is the second generation of that board, and genuinely different hardware: a different processor family, a different CAN controller, a different memory map, and its own signing key. It adds a supply for the analog sensor that the firmware switches on at startup. From the bus, from the installer's point of view and from the commissioning procedure, it behaves exactly like the board it replaces. A V2 fitted in place of a Serial/Modbus with the same settings behaves the same way.

All three carry a different hardware ID and are signed with a different key. That is what stops an image for one from installing on another — see Loading and updating a firmware.

The MUXEN CAN bus

One port, 500 kbit/s, fixed. This is the boat's bus, the same one the screens and the Brain are on.

It is an ordinary 120 Ω CAN bus: two wires plus a common ground, 120 Ω at each end of the segment and nowhere else. The gateway is terminated only if it happens to sit at a physical end. A bus with one termination too many or one too few may work on the bench with a short cable and fail on the boat; it is worth checking with an ohmmeter — 60 Ω across a powered-down, correctly terminated bus.

Unlike a CanCan, this box has one CAN connector. Everything on the equipment side goes through the serial channels.

The four serial channels

The channels are numbered 1 to 4 and that numbering is the same everywhere: on the connector, in the firmware, and in the device the Brain sees for each channel.

Their electrical behaviour is decided by the firmware, not by anything on the board:

The firmware sets	Meaning
Direction	which way the line driver is enabled
Duplex	half duplex (2-wire, RS-485 style) or full duplex (separate transmit and receive pairs)
Line termination	on or off, independently for the transmit and receive sides
Speed and framing	the bit rate, parity and stop bits the equipment expects

There is no jumper and no DIP switch. If a channel is at the wrong speed or in the wrong duplex mode, the answer is a different firmware, not a different board setting.

What each released product does with the channels:

Product	Protocol on the channels	Speed	Framing
010010002 — VE.Direct	VE.Direct, full duplex	19 200 bit/s	8 data bits, no parity, 1 stop bit
010010019 — Frigomar	Modbus RTU, half duplex, transmit-side termination on	9 600 bit/s	8 data bits, no parity, 1 stop bit
010010028 — Blue Airco	Modbus RTU, half duplex, transmit-side termination on	9 600 bit/s	8 data bits, no parity, 1 stop bit

A Modbus segment is a bus like any other: it wants a termination at each of its two physical ends and nowhere else. The gateway supplies one of them when the firmware turns its transmit-side termination on; the far end is the equipment's own.

WARNING

The four channels are not interchangeable with the four channels of a different product. Each application decides what it expects on each channel and how it addresses the equipment there — read its manual before you wire.

Inputs and outputs

Every box in this line exposes these, whatever the application:

	Count	What it is
Relay output	1	a dry contact, commanded from the MUXEN bus
Analog input	1	measured in millivolts, 0–5500 mV range, 12-bit
System LED	1	the local diagnostic — see Common mistakes

There are no dry-contact inputs and no second relay. The generic I/O frame the box publishes has fields for them, and they are always reported as inactive — that frame is shared with other MUXEN device families that do have them.

The analog input is sampled ten times a second and published as raw millivolts. Turning millivolts into litres, degrees or bars is the Brain's job, not the box's.

On the Serial/Modbus V2 board the supply feeding the analog sensor is switched on by the firmware at startup and stays on. On the two earlier boards there is nothing to switch.

Power and mounting

The box is powered from the boat's DC distribution. Follow the mechanical and electrical figures on the product data brief for the product ID you are installing — this manual describes behaviour, not ratings.

Firmware compatibility

A firmware image is built for one product ID and one board, and the three boards are signed with different keys. An image for one board is refused by another before anything is written; the upload fails and the box keeps running what it had.

The software version tells you the generation at a glance: 6.x images are for Serial/Modbus V2, 5.x images for the two earlier boards. The version alone does not separate CAN/VE from CAN Serial/Modbus — both carry 5.x numbering — so read the hardware ID when it matters. See Loading and updating a firmware.