• Overview
• Refurbishing the Controller
• Firmware
• Connections
• Chassis
• Operating Systems and Software
• Parallel Port Programming
• Home Automation Hardware
• Project Extentions

Overview

This project consists of taking an embedded controller donated from local industry and refurbishing it for an automated home controller.  The goal was to program the parallel port, using it as a controller for home automation.
 

Refurbishing the Controller

Firmware

The controller consists of a single board 486 sx computer.  The original application used this board with a custom BIOS chip programmed to interface with a bar code reader and LCD display.  Milcare, the local company who donated the equipment no longer had any documentation on these units and the people who had designed them no longer worked for the company.  Adastra Systems, the single board computer manufacturer explained that this computer board version required parity memory with all the memory chips on one side of the simm (a physical limitation).  When trying to boot the computer using this memory it still did not recognize the VGA monitor or keyboard.  What finally worked was removing all other EPROM's and trying out different versions of BIOS chips from some of the other units.  There were two boards with a version of BIOS chip which booted the computer while recognizing the keyboard and monitor.  These versions were apparently from preliminary designs; the boards that had them were not mounted into the cases.
 

Connections

This board used an unusually small 44 pin IDE connector for the hard drive connection.  This size is typically found in laptop computers.  There were no connectors like it available locally.  An adapter was pieced together by splicing a regular IDE cable to parts that came with the units; comperable pin-out specifications found at Tommy's pinout collection.  This adapter cable provided the interface with an 120 Meg hard drive.  The floppy drive connector used a normal floppy drive ribbon cable connection.  The VGA monitor connector was custom made adapter from a ribbon cable connection on the computer board to a typical monitor connector.  The proper connections were found using the computer board documentation and a monitor specifications in a manual.  The floppy drive, keyboard connector, keyboard, and power supply were salvaged from old PCs.
 

Chassis

The case used by the original embedded controller was used as the case for this project.  It was adapted to contain the computer board, floppy drive and hard drive.  To adapt case to include the 3.5 inch floppy drive and hard drive, two pairs of regular PC drive mounting brackets were adapted to mount the drives in the case and a hole was cut in the sheet metal case for the floppy drive.
 

Operating Systems and Software

The hard drive was partitioned into a 50 Meg DOS partition and a 70 Meg Linux partition.  Both DOS and Linux were installed using floppy disks.  Using the DOS partition to install from, the Linux partition included the basic Linux operating system and a C/C++ compiler and related libraries.
 

Other Applications

Since the requirements for retrofitting these donated controllers have been sorted out, these computer boards may be used for other engineering projects.  For example, some of the computer boards also included components for an ethernet ccard.  Another student has set up one of these computer boards as a diskless terminal for a Linux server.  The rest of the computer boards will be used in engineering labs.
 

Parallel Port Programming

A PC's Parallel Printer Port had a total of 12 digital outputs and 5 digital inputs accessed via 3 consecutive 8-bit ports in the processor's I/O space.

     8 output pins accessed via the DATA Port
     5 input pins (one inverted) accessed via the STATUS Port
     4 output pins (three inverted) accessed via the CONTROL Port
     The remaining 8 pins are grounded

These addresses are in sequential order. For this computer board, the data port is at address 0x0278, the corresponding status port is at 0x0279 and the control port is at 0x027a.

Parallel port programming in Linux adds an additional twist to the parallel port programming examples available on internet.  The best place to start is a basic Linux HOWTO. Here is a simple parallel port example from it.

Each hardware conponent has a related C parallel port program.

• Light control with a switch: light.c
• DC motor control with two switches: motor1.c
• Light control with a motion detector: sense1.c
• Sample program to test all outputs and an input: flash.c
 
Additional parallel port programming information:
• Peter H. Anderson's Use of a PC Printer Port for Control and Data Acquisition
• Ian Harries' Interfacing to the IBM-PC Parallel Port
• Linux par port bit level driver

Home Automation Hardware

     Ademco Passive Infarared Motion Detector model 1852   
AC plug-in adapted for relay control of lights or appliances 
     Switch box for remote control
DC motor control circuit      
 
     Anderson's Parallel Port Test circuit was used to verify the parallel port programming.

Project Extentions

By attaching additional circuits to the parallel port, many more inputs and outputs could be defined.  Using additional inputs and outputs, many more devices could be controlled around the home.