I bought an Xpand X101 shutterglasses but to use it, I needed to figure out how the glasses synchronize with the projector.
As you may already know, the Xpand X101 use an infrared encoded communication.

I don't have access to an Xpand emitter,so I needed to record the Infrared pulses on an Xpand equipped cinema. I cant bring my oscilloscope to the cinema so I build a circuit that measure the pulse timings and send them on an MP3 audio recorder using the serial output of an Atmega8 microcontroller :


To read the data, I just have to plug the PC serial port on the comparator output and play the recorded MP3.

The IR pulses can be interpreted as binary code :


The code that activate the glasses isn't send at every frame. It is send periodically, always after a Ron-Loff command. I don't know the original frequency but it's not important as the glasses only need it once to activate after a communication loss.
I personally send the code every 100ms to get a fast recovery after a communication loss.

I've also made a program to find the code by brute force it (try every combination) but my pair of X101 seems to activate whatever the code so it was not very useful.

Nice work, what did you use to send the signal to the glasses btw ?

Very cool. If I were rich I would hire you to be my personal hacker!

So what are you going to use this for?

I used the timings to program my home-made universal emitter and thus making it compatible with Xpand X101 glasses.
I will do an other topic about it.

Awesomeness man. Now you just need to work out how to read DX info and make emmitters for frame sequential Iz3d drivers and non nvidia glasses!

Sorry but this is beyond the limits of my genius.
I know electronics and microcontrollers, but I almost don't have any knowledge in computer programming.

@Petrus
good job really!!
Can you send me some code/driver you wrote for the emitter, please?

Thanks very much!

All the code and schematic are already here :
viewtopic.php?f=26&t=10183

Great man !
One question I have.
I found xp_code is 0x0 in your code, but 0x0814 in Xpand_X101_ir_pulses.
So what is the difference?

The X101 I bought seems to work whatever the code is, so I put 0x0 and it works fine with it.
The code 0x0814 on the picture is just an example to show how the code is transmitted.

I've made some photos of the inside of an Xpand X101 shutterglasses:


And the most important, the electronics :

I opened it to see how the Pi-cell LCD shutters are driven and if I can improve it. The contrast is quite low on those glasses I estimated it at 150:1.

More to come soon.

So this is how the Pi-cell LCD are driven on the Xpand X101:

Voltage across the LCD :


Voltage on one terminal and the battery negative as the GND :

To get 14V across the LCD, the electronics put the first terminal to a -11V potential and the other to the battery voltage.

The advantage of OCB shutter is the fast response time, the contrast ration is lower than others.
And it switch to dark at a high voltage such as 14V as you mentioned( so far as I know, some OCB shutter need higher than 20V to get a more black backgroud), and 3.3V to get bright transmittance. The color of the shutter is blue or little green when no voltage on it.
Hope it is usefull for you.

I tried to elevate the voltage to get more contrast, but with a higher voltage the angle of vision is reduced.

So PI CELL = OCB ? Wow.

Toshiba made OCB shutter with 5000:1 extinction, also Sony shutter supposed to be pi-cell with 5000:1 and sub 2ms restart time.

yes, Pi cell means OCB technology
I have discussed the OCB technology with some guys from toshiba, it seems their 5000:1 contrast base on a different test method. but anyway, Toshiba masted the best OCB technology in the world