( cached 20011008114515 from http://members.home.net/andrew.g.miller/SX-X10/ )

Design

Use the SX-Stack Evaluation Board to control X10 Home Automation devices via the Internet.

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Goals

• Create an SX Virtual Peripheral interface for controlling the X10 CM17A" Firecracker" remote control.
  • Serial  Input/Output functions interrupt driven.
  • Minimize I/O port usage and interface hardware by using onboard RS-232 level converters.
• Create an HTML GUI which will act as a user interface.
  • Allow ON/OFF/DIM of X10 modules.
  • Display "last known" state of 16 X10 modules.

Hardware

CM17A and RS-232

The CM17A uses DTR and CTS RS-232 signals for communication. These +-12V signals also provide power for the device. The phase relation of signal changes on these lines determine bits 1 or 0 being sent. Under normal usage, i.e. while plugged into the back of a PC, the DTR and CTS lines could be manipulated by X10 software, without interfering with most other uses of the PC's serial port.

SX-Stack and RS-232

The SX-Stack Evaluation Board has an onboard MAX232 line driver and level converter.  Although this onboard RS-232 interface is not used by the SX-Stack HTML demo, it is needed by the utility programs to load HTML data into the onboard serial EEPROM.  Any hardware changes to this interface, must be reversible to allow debugging of the device, and programming of the EEPROM.

A Simple Interface

The MAX232 line driver only provides two output drivers.  These drivers are connected to TXD and DTR for normal serial communication. However, the CM17A does not need the TXD signal, so we can steal the TXD driver and use it for CTS.

This modification proved so simple that I decided to implement it on my SX-DS1W interface board. The complete schematic and PCB are available on my SX-DS1W page.  The board provides a jumper to switch the line driver between the TXD and CTS lines. This allows the CM17A to be unplugged, and the port to be used for debugging, and for programming the EEPROM.

SX-Stack Ethernet Evaluation Board schematic

  Here is the schematic for the SX Ethernet Evaluation hardware as supplied by Ubicom. (PDF)

Software

Source Code       (SRC)

Assembler Listing (LST)

Assembler

• SX-Link v 1.30 from Parallax

Base Line code

• Ubicom's Ethernet SX Stack Source Code.

  
  There were a few changes needed to get this code to assemble under SX-Link v 1.30.  Ubicom must have used an earlier version of the Assembler.

HTML

• Here are files which are loaded into the SX-X10 to provide the demo GUI.

  • REMOTE

  
  These raw HTML files are processed by the SX-X10 replacing occurrences of special characters with the last known state of X10 devices.

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Reference Documentation

SX

SX-Tech

SXList Fast Embedded Ethernet Design Challenge and Contest

Ubicom: Ethernet SX Stack Evaluation Kit

Ubicom, Inc. - Virtual Peripheral - Ethernet Source Code

Ubicom Ethernet SX-Stack Demo

X10 Home Automation

X10.com