Em 16/8/2011 14:23, alan.b.pearce@stfc.ac.uk escreveu:
>> Lost somewhere in the sands of time was an interesting serial protocol u=
sed
>> on TI graphing calculators. There's plenty of good reference material on
>> Google, but it basically worked like this:
>> Two bidirectional lines with pull up resistors. The sender starts by pul=
ling
>> one line low, the receive end acknowledges by pulling the other line low=
..
>> They both release and start again. Zero's and ones were signified by whi=
ch
>> line the sender pulled low.
>>
>> Works _very_ well in a busy processor since every bit waits for an ack. =
Data
>> rate could be quite high with the addition of interrupts if so inclined.
>> Opto isolation may be more challenging, but seems workable.
> Yes, I learned about it when I bought a TI-83. I figured it is a very use=
ful protocol to use between PICs, and it is self synchronising, so clock sp=
eeds are don't care.
>
>> I've always been surprised this hasn't found it's way into more
>> applications.
> Just been listening to the link that Harold Halliken posted with the piec=
e on Patent Trolls ... it's probably patented somewhere ...


The patent is probably expired or expiring, this model was released 15
years ago. The protocol hopefully may be even older.

Isaac



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