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The Sony IR Decoder code is written
in "C" and programmed into a PIC12C509 using a Parallax
(www.parallaxinc.com) programmer. The Sony remote control signals
are 12 bits long and have a 2 ms start bit. I use the PIC timer
to measure the start pulse and then I time each of the high portions
of the 12 bit frame. A 700 us wide high portion is a "0"
and a 1200us wide high portion is a "1". To reverse
engineer the Sony remote signals, I used a Sharp IR receive module,
powered it up and put a oscilliscope on the output lead. Holding
a remote button will cause pulses to appear on the scope as long
as you hold the button. I found for the Sony that some bit frames
were always "1" or always "0" for TV and VCR,
which allowed me to define an 8 bit value for each of the 12 bit
Sony codes. Take a look at my code. I do a loop looking at each
bit frame to determine if it is 700us or 1200us. I did three other
important things to avoid false hits. There must be a valid start
pulse (2-4 ms low), the generated code must be the same twice
in a row, and the generated code must be one of the ones I've
placed in a look up table in ROM. These checks keep the decoder
from outputing bad values and from triggering on noise like sun
light.