Welcome to
BoatBus, an Open Hardware and Software Project
A chronicle of my nerd hobby

Sure, there is open software out there. Linux comes to mind. And there are even a few open hardware projects. This is intended to be a completely open embedded system. Schematics, source code, and PC layouts are all available for you to look at, use and possibly contribute to. Most businesses need to keep designs proprietary in order to maintain a competitive advantage. This is not a company, it's a part-time endeavor and I am doing it purely for my own enjoyment. And I wish to share it with other people.

What BoatBus is in the most general terms, is a system for collecting data from the environment, and displaying it for humans to read. It Also allows the human to control some aspects of the environment. The first system is intended for both home and boat use. Common functions between a home and a boat: collecting weather and environmental data, power usage, controlling lights and sound, displaying in several convenient locations.

I'm Dave Erickson, an EE. I've worked at several companies in the Boston Route 128 area since graduating WPI in 1976. Two years at HP medical, then three at a startup: Octek, where I was half of their consulting group, and where we designed just about anything for just about anyone. Then Datacube as Director Engineering for 15 years, doing real-time Image processing. Then 4.5 at Analogic as Chief Engineer of the Test and Measurement division. Then to Zoll Medical, working on Defibrillators, then a startup stint and curently at Teradyne, where we make big ATE machines. My skills are mostly analog and digital hardware design, but along the way I began doing assembly programming, and then C.  At home, I build electronics for home and boat. I like to mix analog and digital hardware design and software in a complete system with sensors, data acquisition, processing, display and a bit of communications thrown in.

For the past few years I've been working on a networked display and data acquisition system. I did the first generation of a similar system about 10 years ago. It used a surplus LCD panel, a 68hc11 micro, and a bunch of code and custom hardware. It was a single box system designed to provide my boat with a bunch of marine-type data: wind speed and direction, boat speed and direction. It also provided rudimentary navigation by maintaining a dead-reckoning track.

Since then, LCDs and FPGAs have gotten a bit better, processors are faster and more integrated, and C tools have gotten a bit better. I decided to network this system in order to support remote data acquisition and display. Meanwhile chips have gotten smaller, requiring more advanced prototyping techniques. But the good news is that companies like expressPCB now offer decent PC boards at prices hobbyists can afford. Their Mini Board service is three 2.5 X 3.8" boards for $51 plus $10 shipping, delivered in less than a week. And the CAD tool is free also.

BoatBus I

The name BoatBus is my generic name for my old boat project, BoatBus. While it worked OK, it was really a functioning prototype, and had some limitations. In reality it was not a bus. It consisted of a single box containing all the signal conditioning, acquisition, processing, and display circuitry. This made it larger than I'd like a display to be. It also meant that all the low level analog sensors had to be wired directly to the main box. I used the system for two years aboard my old boat. When I moved to a newer, larger boat, I never installed it. It's size was inconvenient and not really worth the hassle to wire it all up.  Plus, GPS now offered most of the nav features that BoatBus had. Also it had no expandability: to add a new sensor or a second display required significant re-engineering. But it was a good first step towards the ultimate system.

The gutsThe old surplus LCD display was a Hitachi HD215XP. It was not backlit, and had the annoying habit of completely blacking out in the heat of direct sunlight. I learned not to use a first generation LCD outdoors. Also the form factor required a large enclosure, and there is no room for large boxes in the cockpit of most boats.

Here are the innards: the 68hc11 processor board on the left with the original Actel LCD1 controller. The analog board is the real PC board on the right. I used 96 pin DIN connectors to connect them together. Tucked in the upper right corner is a the +5V switching power supply which is a National evaluation board. The entire system drew about 120 mA current from +12V

Breakout BoxThe +12V power and the sensor wiring comes from the 25 pin D cable on the lower right. It connects to this breakout box with connectors for the various sensors

I decided I'd also like LCD displays at home, to display weather, house power use, and to control my house-wide stereo system. I began a wish list of features for the boat and for the home.

  • Better, more readable display with backlight.
  • Faster processor to allow faster displays without programing tricks
  • A low cost serial bus to communicate data
  • Ability to use multiple displays and sensor modules

  • BoatBus 2 Overview
    The decisions of what type of displays, how to architect the communications, what processor, tools, etc are all journaled in these pages. Here is an overview of the system designed to meet the above goals.

    The system consists of nodes connected via an RS485 network (bus). The bus consists of four wires that are daisy-chained to each node. The wires are: D+, D-, GND and +12V. That way each node can be powered off the network, assuming it doesn't draw more than a few hundred mA. All the network requires other than nodes and wiring is a 12V power supply at about 1-2A. For home, a small switching supply provides it. For the boat or for automotive applications,  it can run directly off the +12V battery source with minimal conditioning.  The wiring is simple CAT-5 twisted pair which provides 4 extra wires.  It uses simple screw terminals so the system can be easily field wired with just a screwdriver.

    Nodes can be or do just about anything, but for now I have designed two types: the first type is display nodes. These generally collect data off the bus (recieve) and display it on a graphics LCD. The other types are data collection nodes. These interface to sensors, make measurements, and send the data to the bus. Any node can either recieve or send, or do both.

    This sounds simple enough, but most of the RS485 'protocols' in the world are Master (typically a PC) -centric. A PC masters the network, collects data from numerous slave nodes, and then displays or stores the data. I wanted to eliminate the concept of a single point to collect the data, and definitely eliminate the PC. In a boat or a house, one may want multiple displays. Using most protocols, the master PC polls each node, collects the data and then sends it to the displays if there are more than one. This seems wasteful since data then is on the bus twice. I wanted a more democratic system where each node can send data if it has some to send, and each display can recieve it and display it if it wants the data. A broadcast system. Any RS485 network does need a  way to coordinate traffic and eliminate collisions, so some bus timer (master) is needed, but it can be merely a traffic cop. It doesn't need to process the data, just say who's turn it is to go next.

    Dave's rule # 7: Before you build something for the boat, build one for home or for the car. Much easier to get the bugs out when not surrounded by salt water.  I have played with home control and weather stations in the past. I could  see the value in having a few displays and control panels around the house.

    The details on the communications protocol can be found here
    The decision of which
    processor to use is here.
    Discussion of graphics LCDs is here.
    The first node, used to collect weather sensor data for boat and home is here.

    BoatBus 2 Display

    Here is the hardware for the display node. I needed something to show for the effort and thought so far, so I installed the prototype hardware in an enclosure, along with a QVGA LCD panel.  Here is the proto of the AVR Mega128 processor with an LC10X type LCD controller. The empty sockets on the top left are from the old 68hc11, SRAM and EPROM that I removed. The Mega128 is on a prototype adapter from http://www.devrs.com/store.   In the upper right are the LCD controller FPGA,  8 pin config EEPROM, and display RAM . The IC and caps on the right are the V- power supply for the LCD. JTAG ICECube for development is lower right.


    Here it is with the above controller board mounted behind the QVGA LCD in an oak enclosure, and nearly ready to install in the kItchen. The overlay and buttons are missing. The holes below the display are for 5 push buttons to control the display. Someday.... Meanwhile this display provides me and my family with the outdoor temperature and wind speed / direction, and a display and plot of our home energy use.

    BoatBus Home
    BoatBus Story
    Weather Node
    LCDs are a pain. but fun!
    AVR Processors
    Communications via RS485
    How I prototype, and the Lab

    Last Updated: Apr 25, 2008