Fathom-X Documentation



Introduction

The Fathom-X Tether Interface Boards provide a high-speed, long-distance Ethernet connection to an ROV or other remote platform. They’re designed for use with the Fathom tether, standard Cat5 cable, or even a single twisted pair of wires. This board uses the Rak Wireless LX200V20 module, which leverages the robust HomePlug AV (IEEE-1901) standard for sending Ethernet through powerlines.

The Fathom-X board is also part of the Advanced ROV Electronics Package and works well in conjunction with the Raspberry Pi, Pixhawk, and ArduSub Control Software.

Features

  • 80 Mbps Ethernet over two wires (per our own bandwidth testing)
  • 300m+ tether length capability (published capability of 2000m)
  • Plug-and-play with no setup involved
  • Onboard switching power supply with 7-28V input range
  • USB Mini-B connector for powering directly from a computer on the topside
  • Indicator LEDs for power, link, and data
  • Included 6” Ethernet cable for connection to onboard computer

Quick Start

  1. Connect two wires from the tether cable to the terminal block
  2. Power each board with either a USB connection or a 7-28V input to the small terminal block
  3. Connect an Ethernet cable and the connection should become active immediately

Specifications

Function Diagram

Specification Table

Item Condition Value
Electrical    
Supply Voltage Terminal Block 7-28 volts
Supply Voltage USB 5 volts
Max Power Draw 2.5 Watts
Performance    
Max Practical Bandwidth   80 Mbps
Physical Layer Bandwidth   200 Mbps
Working Frequency   2-30 MHz
Max Tether Length (Published)   2000 m
Max Tether Length (Tested)   300 m
Physical    
Operating Temperature   -20 to +85°C
Storage Temperature   -40 to +85°C
USB Connector Type   USB Mini B Female
Tether Wire Gauge   12-30 AWG
Power Wire Gauge   16-26 AWG
Dimensions   64 x 46 mm
Screw Hole Spacing   57 x 40 mm
Screw Hole Diameter   3.3 mm

Schematic

The EagleCAD files for the schematic and board are available on our GitHub page.

Installation

Normal Scenario

In most cases, the Fathom-X setup is simple. Once powered, it acts as a transparent Ethernet bridge to extend any Ethernet connection through the tether.

The four screw holes are identical to those on the Fathom-S ROV board, so they can be interchanged quickly.

With Fathom-S

The Fathom-X board can be use with the Fathom-S board to provide the features of both, simultaneously. Additionally, the screw hole pattern is identical so that they can be stacked together with stand-offs.

The use both board together:

  1. Connect the tether wires to the Fathom-S board normally.

  2. Add jumpers between “Pair 4” on the Fathom-S board and the large terminal block on Fathom-X. Connect 4+ to “+” on the terminal block and 4- to “-“ on the terminal block.

  3. That’s it, both boards will function normally, including the power on/off feature of the Fathom-S board.