We've had a robot vacuum at home for a couple of months and now we've got one for the office at work. The XR at home came with a virtual wall that produces an infrared beam that the vacuum just wont go anywhere near. The Vileda at work didn't come with one (nor a remote or a dock) which would of been handy; there's a couple of areas we'd like to keep it away from.

On the front of the Vileda there's a 360 degree IR sensor that both my XR and the Roomba's have - although the Vileda doesn't come with any accessories that it would need it for (dock, virtual wall) - nor at present does Vileda appear to sell any. Making the assumption that both of these had probably been - for at least some part - reverse engineered from a Roomba, I took the virtual wall from home into work and tested it against the Vileda; it too wouldn't go any where near it :)

I'm not really allowed to open up the the XR (or it's accessories) at home as it's technically "in production", but initial thoughts were that I just needed to be able to detect the beam coming from the virtual wall myself and then re-create it. Before doing that though I thought I'd see if the Roomba virtual wall had been reverse engineered already and see if I could implement that, and if it caused the XR to flee.

  "The Virtual Walls generate a 1ms ON, 1ms OFF signal continuously.  The 1ms ON is a 38Khz PWM pulse."
  

Excellent. A little more searching and I found this post on the arduino forums; right at the bottom of the code block there's this function:

// this will write an oscillation at 38KHz for a certain time in useconds
void oscillationWrite(int pin, int time) {
 for(int i = 0; i <= time/26; i++) {
   digitalWrite(pin, HIGH);
   delayMicroseconds(13);
   digitalWrite(pin, LOW);
   delayMicroseconds(13);
 }
}
  

So I swiped an IR LED from an old TV remote and after a bit of messing with my phones camera (it doesn't have an IR filter so I could use it to see the infrared) and the blink example program, I wrapped oscillationWrite() up in loop() so that it did a 38KHz pulse every millisecond:

void loop() {
  oscillationWrite(irled, 1000);
  delayMicroseconds(1000);
}
  

I was pretty hopeful that this would work and went to test it with the XR, but it completely ignored it. Assuming one of the timings was off I hooked the scope to the LED pins. The millisecond pulse was a little off but not by a lot, but the 13 microsecond pulses that make up the 38KHz carrier were coming in at 18 microseconds, probably due to the amount of code that's executed by digitalWrite(). Rather than mess around using port manipulation to speed up toggling the pin, I just knocked the delay time down to 8us to compensate.

Testing again with the XR proved successful, with it backing away whenever it got to close to my improvised beam :) for a complete test I trapped the XR between my beam and the virtual wall it came with. My 'wall' is across the bottom of the door next to the olde worlde CD player and the real one is the black object on the floor next to the sofa. Everytime it sees a beam, it backs away. (The bumper is actually at the front - it's just that in the video, the XR spends most of it's time going backwards!)