Control and integration

Infrared control

IR, the NEC protocol and the Diva remote codes

The Diva can be driven entirely by infrared, which is usually the easiest way to fold it into a remote or a control system you already own. It accepts infrared in three separate ways, and they are not interchangeable.

An infrared remote does not send light continuously. It flashes an LED at a carrier frequency, commonly 38kHz, and the receiver looks only for light flickering at that rate, which is what keeps sunlight and room lighting from being read as commands. The pattern of bursts and gaps around the carrier is what carries the data.

NEC is one of the older and more orderly ways of arranging that pattern. A frame opens with a long lead burst, then sends an eight-bit address identifying the device, the inverse of that address, an eight-bit command, and the inverse of the command. The two inverted copies let a receiver reject a frame corrupted by interference, which is why NEC survives across a room reliably. Holding a button sends short repeat frames rather than the whole message again.

Pronto hex is a different way of writing the same thing down. Instead of naming a protocol it lists the carrier frequency and the raw on and off timings as hexadecimal words, so a control system that knows nothing about NEC can still reproduce the waveform. If your system accepts device and function numbers directly, the two NEC bytes are all it needs; if it wants raw timings, give it the pronto hex.

Infrared control on the HDfury Diva

Three routes reach the unit. The IR window is the receiver built into the Diva itself, and it is where an IR TX LED is stuck when a control system blasts directly at it. The IR RX jack takes the supplied 9ft sensor cable, for a unit hidden in a rack or a cupboard while the sensor sits somewhere a remote can see. The Input jack is a direct wired connection from a system controller, using no light at all, which is the cleanest option when the controller can output infrared electrically.

The codes themselves are NEC format. Each entry gives the address and command bytes as two hex values, written in the form NEC 0x7a 0x4e, followed by the full pronto hex string for that function. The complete list is a searchable table on the IR codes page, is downloadable, and is also included as a text file in every firmware update package, so use the copy that came with the firmware you are actually running. The community has submitted the list to Logitech Harmony and to iRule, so on those platforms the unit may already be listed.

Wherever a setting is a toggle, the codes come in pairs, with a separate code for on and for off rather than one code that flips the state. That is deliberate: a macro can put the unit into a known state without having to know what state it was in beforehand. Every option in the OLED menu is also available by infrared, over IP and over RS232, so nothing is lost by driving the unit entirely from a remote.

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