FIRST POST: I've written an excel spreadsheet that takes a Pronto HEX code as input and converts it to a format for a proprietary IR blaster. Since we don't know what's on the receiving end, the only problem I encountered was that the Pronto HEX format does not tell me the duty cycle (i.e., time ON vs OFF in a single IR pulse). I messaged Mr Pronto (Barry) and he didn't see a way to reverse engineer the duty cycle from a Pronto HEX code either. So, I performed the conversion for a number of Pronto HEX codes for Samsung and hard-coded a duty cycle of 1/3 and it worked great on the Samsung TV in our lab.

Right now, I'm researching whether the duty cycle can be assumed based on the frequency (e.g., do all 38kHz IR protocols use a 1/3 duty cycle?). Has anyone assembled a list of IR protocols that contains the frequency and duty cycle for each? I'm not interested in protocols that are no longer used.

And, before I convert this spreadsheet to code, I'd like to test my Pronto HEX converter on IR codes for devices (we have a bunch TVs in our lab) that use all of the popular IR protocols of today. I've read that Sony uses the SIRCS protocol, Philips uses the RC5/RC6 protocols, Panasonic uses the Matsushita protocol, and the NEC protocol is used by a number of manufacturers but I don't know who they are. I'm sure there are other AV manufacturers that use these and other IR protocols. Has anyone assembled a list of AV manufacturers and the IR protocol(s) they use?

What we're building is definitely cool but I don't get to talk about it yet. Soon my IR Master friends... soon.

Best regards,

- IR Padawan

Nearly every known protocol has been documented in IRP notation which specifies duty cycle:
[Link: hifi-remote.com]

So simply download IrScrutinizer and look at the IrpProtocols.ini file:
[Link: hifi-remote.com]

As for which manufacturers use which protocols, that's an exercise in futility. Most have used many different protocols over the years. The most comprehensive list we have is the JP1 Master list: [Link: hifi-remote.com]

Thank you IR Master Dave for your response. I downloaded the documents and program you referenced but unfortunately I don't see where the duty cycle is stated for a given protocol. For example, the IrpProtocols.ini file describes the NEC 1&2 protocols as follows:

[protocol]
name=48-NEC1
irp={38.4k,564}<1,-1|1,-3>(16,-8,D:8,S:8,F:8,~F:8,E:8,~E:8,1,^108m,(16,-4,1,^108m)*)\
[D:0..255,S:0..255=255-D,F:0..255,E:0..255]
EFC_translation=LSB comp
[documentation]
This protocol signals repeats by the use of dittos.

[protocol]
name=48-NEC2
irp={38.4k,564}<1,-1|1,-3>(16,-8,D:8,S:8,F:8,~F:8,E:8,~E:8,1,^108m)+ \
[D:0..255,S:0..255=255-D,F:0..255,E:0..255]
EFC_translation=LSB comp
[documentation]
This protocol signals repeats by the use of dittos.

The documentation also states:

1. General principles of IRP notation
1.3 The execution process
...The carrier frequency was described in 1.1. The duty cycle is the percentage of the cycle time that the IR light is on. A carrier frequency of 40kHz means that there are 40000 cycles per second, so each lasts 25μs. If each cycle consists of the IR light being on for 9μs and off for 16μs then the duty cycle is 9/25, or 36%. The frequency varies substantially between one protocol and another and is given in the IRP notation. The duty cycle is a matter for the implementation and is not given in the IRP notation. Duty cycles are typically around 33%. A larger value means that the batteries in a remote control will last less long but the range of the signal will be greater.

14. Execution model
14.1 Introduction
... Also set externally is the duty cycle of the carrier generator. This is typically 33% or thereabouts, but again it is outside the scope of the IRP notation.

14.4 Execution
... By means outside the scope of IRP notation, this binds certain names to values in the global environment and sets the carrier generator duty cycle.

Would you be so kind as to point out where the duty cycle is defined or how it can be calculated in the above NEC protocol examples? TIA

- IR Padawan

I stand corrected. But those guidelines should get you close.

Welcome to the community, Padawan,

The reason that the duty cycle plays no important role e.g. in this forum, is that it really hardly matters. Almost all of modern consumer electronics use a demodulating chip, for example [Link: vishay.com]. This chip removes both modulation frequency and duty cycle. Cf, the wavelength of the IR light. (Having said that, I have somewhere heard of a protocol which used variable duty cycle to signal battery state of the sender.) By lowering the duty cycle you save some sending energy, sacrificing some range and reliability. As alternative, you can just lower the sending current.

Information on a duty cycle is simply not present in the Pronto HEX form, just like wavelength...

@mdavej: The IRP form according to John Fine and the Graham's document you linked to, does not allow specifying the duty cycle either. However, it is contained in my extensions to the IRP ([Link: harctoolbox.org]) although at least presently not really used.

Gentlemen,

First, thank you for your posts. @mdavej: it's not my intention to correct anyone... I'm the student and you guys are the teachers. That being said, @barf, are you saying that the duty cycle is irrelevant? For example, the same IR code with 25%, 33%, 50%, and 66% duty cycles would be received and understood by the corresponding device (e.g., TV, blu-ray player, digital media player, audio receiver) in all instances? I would be thrilled if this is true because it would mean that I don't need to worry about duty cycle any more. Anyone else want to weigh in on this one?

- IR Padawan (for @barf, a Star Wars reference)

I know it's been 5 years, but did you ever get this conversion program working?