PS/2 Keyboard IR Receiver

Posted on Feb 7, 2014

A few years ago, someone gave me a small wireless infra-red keyboard, part no. RC-KB2, designed to be used with a Kenwood audio system. As soon as I saw it, I wanted to discover it`s transmission format. Why Because I would then be able to build a small receiver which would allow me to use this keyboard on a PC with a PS/2 port. Two years later,

PS/2 Keyboard IR Receiver
Click here to download the full size of the above Circuit.

I finally found (or took ) the time to do it. This page`s purpose is to document the project. Maybe someone else would like to use a keboard like this one with their PC In any case, the receiving part of the code could be rewritten for other keyboards or even regular infra-red remotes. When the keyboard emits infra-red, it is not continuously. In fact, it modulates the infra-reds at a frequency between 35 and 38 Khz. I did not measure the exact frequency, but I assume it is in the 35-38 khz range because an infra-red receiver salvaged from a VHS Vcr receives the signal correctly at a pretty good distance. After looking at the receiver`s output with a digital oscilloscope, I understood how the data was transmitted. As my infra-red receiver had an active low output, a low level in the following diagrams indicates that an infrared wave was present. Right after the attention signal, the keyboard sends the data bits. The time elapsed between active pulses (560us) varies depending on the bit value being transmitted (1 or 0). A long time (approx. 1640us) represents a 1 and a short time (approx. 560us) represents a 0. I compiled a list of the codes emitted by most keys on the keyboard. The [shift] keys cannot be paired with all keys. The [Room B] keys act as a kind of [shift] keys but they cannot be paired with the same keys. Unlabeled keys on the keyboard do not generate events. This keyboard was designed for a specific purpose....

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