Originally posted by zeitghost
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Not really.
It's just on/off modulated infra red, using a manchester encoding scheme at the standard frequency of 38kHz.
It's unusual in that the data stream is long enough to encode the entire alphanumeric character set (which is how you can get a keyboard that works with the Sky box).
I just implemented the on/off key, the sky button, and the digits 0 to 9.
It runs on an ancient 20MHz 286 compaq portable III under dos... and nothing else coz it uses timing loops to generate the 38kHz.
The infra red led is connected to one pin of the centronics parallel port.
What I've never completely sussed is how the box determines that you've kept a key pressed, I suspect it's in the repetition frequency of the data stream.
If you keep the same button pressed on the sky zapper, the box just sees the one key press.
If I do the same on my software, the box sees a succession of presses, and the only difference I can detect is the prf of the ir data... it's about 80ms for the zapper and about 120ms for my software.
Bored yet?
It's just on/off modulated infra red, using a manchester encoding scheme at the standard frequency of 38kHz.
It's unusual in that the data stream is long enough to encode the entire alphanumeric character set (which is how you can get a keyboard that works with the Sky box).
I just implemented the on/off key, the sky button, and the digits 0 to 9.
It runs on an ancient 20MHz 286 compaq portable III under dos... and nothing else coz it uses timing loops to generate the 38kHz.
The infra red led is connected to one pin of the centronics parallel port.
What I've never completely sussed is how the box determines that you've kept a key pressed, I suspect it's in the repetition frequency of the data stream.
If you keep the same button pressed on the sky zapper, the box just sees the one key press.
If I do the same on my software, the box sees a succession of presses, and the only difference I can detect is the prf of the ir data... it's about 80ms for the zapper and about 120ms for my software.
Bored yet?
not atall - fascinating stuff - please continue.
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