X10 PLC

1. (c) 2013 R. Newman University of Florida X10 PLC

2. What is X10 • Narrowband PLC for home automation (domotics) • International and open industry standard • 13 manufacturers (including GE, Panasonic) • Developed in 1975 by Pico Electronics (Scotland) • First products shipped in 1978 • First general domotics technology, most widely available • Modules addressed with house and unit codes • Comprises • PHY – modulation, coupling, etc. • DL – frame format • AL – command language

3. X10 PHY • Transmissions immediately after zero crossings (within 200 usec) • Less noise at zero crossings • Line cycle provides synchronization • 120 KHz carrier – sent as burst (1 msec) • Repeated at 1/3 and 2/3 half line cycle for 3-phase systems (to be at zero crossing for all) • One bit per zero crossing • Data bits repeated in inverted form in next half line cycle (like biphase encoding)

4. X10 PHY • 1 msec burst repeated 3 times in half line cycle

5. X10 symbol coding • ASK modulated biphase encoding • 1 is sent as a burst at zero crossing, followed by absence of burst at next zero crossing • 0 is sent as absence of burst at zero crossing, followed by burst at next zero crossing • Rx acceptance window begins 250 usec and ends 900 usec after zero crossing • >= 48 cycles of 120 KHz = 1, else 0 • Bits sent as ASK NRZ-mark during start code (like preamble)

6. X10 Code Transmission • Complete transmission block takes 11 line cycles

7. X 10 Transmission Block • Start code bits not repeated • Makes unique, non-data code • All other bits repeated in inverted form

8. X10 Transmission Blocks • Start Code 1110 starts every TB (2 LC) • House code is 4 bits (4 LC) • Number code or function code is 5 bits (5 line cycles) • Complete transmission block repeated twice with 3 line cycle idle gap between • For reliability – copy code • Dimmer commands (bright and dim) are exceptions – sent continuously with no gap

9. X10 Codes • 4-bit House Code to identify devices in same home (actually, identifies a set of devices regardless of where they are) • For usability, lettered A-P • 5-bit Key Code • Number code – sent when number button is pressed – D16 = 0 • Function code – sent when function button is pressed – D16 = 1

10. X10 Codes • Number codes used to address modules • Once addressed, a module responds to all command codes • Become “unaddressed” when next “address” message is received, or when “all units off” command received • Codes used to • Turn lights on/off, dim/brighten • Open/close shutters • Read meters/status

12. Notes on Codes • Hail • Used to poll for devices with same house code in range • If receive Hail ACK, installer knows to use a different channel • Extended data code • Used for transmission of digitized analog data • Sent in 8-bit bytes • First byte may be length field • No gaps between bytes (so no confusion)

13. Extended Code Access Protocol • Extended codes can take significant time • Need to avoid collisions, detect and resolve them if they do occur • No priority levels • Listen for idle medium • Wait random time of 8, 9, or 10 half cycles • Restart timer if detect a ‘1’ • Detect collisions • When transmitting, listen during ‘0’s for ‘1’ • If ‘1’ detected, abort and restart access

14. X10 References • http://www.smarthomeusa.com/info/x10theory/ • http://software.x10.com/pub/manuals/xtdcode.pdf • http://www.homecontrols.com/FAQ_Library • http://www.x10.com/automation/automation_modules.html