Vermes
Advanced Member level 4
It is a solution for how to make a Media Center of a computer. This device uses a remote control for N-box which is equipped with a number of buttons such as PLAY, PAUSE, RECORD. To make this remote control work with your PC, you have to make some tests with use of oscilloscope and microprocessor. In the standard system of IR transmission from the remote control, there are three time intervals between low states: short – logic 0, long – logic 1 and very long – start the frame. The remote control then sends such a code by giving each bit separately.
There is a lot of time intervals. Every pressing the button of the remote control causes sending 2x 2x 8 intervals.
Here you can see first two:
First 8 – standard start – always the same for every button
Second 8 – including different intervals 2, 5 and 6, depending on the button
Third 8 – standard start – always the same for every button
Fourth 8 – including different intervals (2 if it is equal to the value from the second 8, hold the button, if not – single press), (5 and 6 – the same times as in the second 8 – this combination directly points the button)
Sample interval times measured:
Button x:
17 35 21 48 23 24 19 38 205*
17 |16| 15 |22| |15| 40 16 15 227*
18 34 22 47 24 23 20 37 205*
17 32 32 21 16 40 16 15*
Button y:
18 34 22 47 24 23 20 37 204*
17 |17| 15 |22| |21| 32 15 15 231*
17 34 22 47 24 24 19 37 205*
17 34 32 22 22 32 15 15*
This method of measuring is useful to work out the buttons.
The receiving device is equipped with TSOP1736 on a cable derived outside the housing. IR signal is processed to TTL and fed to int0 of Attiny2313, and then by means of measuring time between interrupts, is able to recognize the button and send its code to RS232. A free guider with Silitek plug should be installed on your PC to receive data from the receiver.
The device has one programmable button. Connect Pinb.0 to the ground and press a button of the remote. After that, pressing the programmed button results in low state occurring on Pind.4. Long press if recognized, so there will be low state on the output until you release the button on the remote control.
The output can be connected to the power button on the main board, so that even if the PC hangs, it can be easily switched off from the remote control. Just hold your finger on the remote control until the computer is switched off.
Presented here device uses resonator 4MHz, because if it had no external quartz, heating the Atmel in the computer could have resulted in damage of the receiver.
Link to original thread (useful attachment) - Pilot od N-Box do sterowania komputerem Media Center