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Original thread:
Post 12 made on Thursday September 23, 2021 at 18:37
Lyndel McGee
RC Moderator
August 2001
On September 22, 2021 at 19:38, ask4mikie said...
Cool. Sorry to bother you.

It's not a bother, just that I'm kinda swamped at work and an answer explaining the NEC IR protocol is not a 1 or 2 liner.

The first paragraph above, I thought would cover what folks wanted to know and never expected anyone would want an explanation of how to decode the actual data in the IR codes I posted. :-)

Apple IR Protocol

Apple codes use a specialized version of the NEC protocol and contain a checksum bit and an 8 bit Pair ID and devices 224, 229, and 238. Device 224 is used for Pairing and normally not needed. The codes below were generated with IR Scrutiner's Apple Protocol.

Apple Protocol is such that it includes a
8 bit Device (0-255)
8 bit Subdevice (0-255)
1 bit Checksum (0 or 1)
7 bit Function (0-127)
8 bit Pair ID. (0-255)

Altogether, these make up 32 bits total and is why the Apple Protocol is an extension of the NEC protocol.

NEC protocol is 32 bits broken apart normally as:

8 bit Device (0-255)
8 bit Device Complement (1s complement where 1 bits become 0) (0-255)
8 bit Function (0-255)
8 bit Function Complement (1s complement where 1 bits become 0) (0-255)

If you'd like to dig into how to decode the IR codes I posted, I can highly recommend Barry Gordon's very old document that describes the original NEC format. You can find the HTML version here.


It's also available as a Word doc under the User Written documentation of the Classic Pronto Files section here.


Last edited by Lyndel McGee on September 23, 2021 20:33.
Lyndel McGee
Philips Pronto Addict/Beta Tester

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