This section describes some of the results of using the IR Analyser.
There are several characteristics of an IR signal. This varies with each manufacturer. Within a manufacturer, there are multiple devices to be controlled and each device has multiple functions. The various characteristics of the signal itself are listed below.
A pulse train using space encoding is shown below. The various parts of the signal are shown and explained below. Most of this applies to other encoding types as well.
Besides these characteristics, there are a few others related to multiple codes in a transmission.
Almost everyone uses Space Encoding. There are some exceptions - Pulse Encoding is used by Sony, Phase Encoding by Philips, Grundig and a few others. Quite a few manufacturers use a particular Space Encoding scheme.
All signals for all devices are stored in an XML file that acts as a database for the UI used in the IR analyser. The simplest way to access all information I have collected on remote controls I have access to, is to see the XML file itself. To look at the waveform produced by each device for a particular function, use an adaptation of the analyser UI. It is the same program but has been adapted to an applet environment.
A table of the characteristics for some of the remotes are listed below. All timings are in uS.
I used a JVC video remote. It has a setting for a TV as well.
JVC uses space encoding. It has an end pulse but no stop pulse. Retransmissions consist of the same signals without the header. The gap is the duration between the end of the pulse train and the beginning of the next.
I used a Sony VCR remote which also has a setting for a TV. I also used a camcorder remote.
Sony is one of the few(only?) that uses pulse encoding. The entire pulse train is repeated for retransmissions. Sony uses a 12 bit code but some functions use a 15 bit code. The only 15 bit codes I have encountered are for some camcorder functions and G Code related functions for a VCR. The gap is the duration between the end of the pulse train and the beginning of the next.
I used the remote for the Thomson Set-top box. An end bit is transmitted after the last bit. A stop pulse followed by an end pulse is sent for retransmissions. The stop pulse is separated by the gap time from the start of the header pulse. Keeping the button pressed sends stop pulses repeatedly. The stop pulses are sent after every 100ms i.e. the rising edges of successive stop pulse are 100ms apart. The first four bytes are always E17A. The next two bytes always have the last two bits set to zero. The next two bytes are the ones complement of these bytes. Using the ones complement results in equal number of zeros and ones and the signal will have the same duration irrespective of the function. This code can have only 64 combinations of which 37 are used.
It can be used to view the waveform for a manufacturer, a device and a function. Timing values are also displayed. Two waveforms are displayed - the white one on top showing the entire waveform consisting of one or more transmitted codes and one or more yellow traces displaying each transmitted code. The generated waveform is then analysed. Each part of the waveform is indicated as header(blue), one(green), zero(red) and footer(light blue). Two hairlines are displayed and can be dragged to measure timings. The absolute time and the difference between the two are also displayed in uS.