Controlling hifi volume with PIC and Infra-Red

[fergcu]

Hi all...
I'm doing a project at the moment which involves PIC (specifically a 16f877). As one of its functions, I am wanting (or hoping!) it to turn the volume of my Sony Hi-Fi (DHC-MD333) up and down remotely. I'm at a bit of a loss as to how to go about this... I'm assuming that it can be done by using an IR LED/Bulb that is turned on and off in a certain sequence (which should be pretty simple with an 877 - let me know if it isnt!!).

The part which im stuck on is what the code sequence would be for volume up and volume down, and at what speed/frequency (Im assuming that it has to be at a certain frequency).

If anyone would be able to shed some light onto this, I would be extremely grateful.

Thanks for your time,
Ferg

 

[Nigel Goodwin]

Check my PIC tutorials, where I give details of Sony remote control systems - both receiving and transmitting them!.

 

[fergcu]

Thanks Nigel, that should be quite useful. However (and im probably being stupid), but i cant seem to work out the actual code that is transmitted by the remote for, say volume up.

This i show i think I should send the code for volume-up on my midi-system:

firstly, send the start pulse:
set IR-LED to 1 for 2.4ms
set IR-LED to 0 for 0.6ms

Then send the command code (volume-up):
this is where im unsure... how did you work out the code?
(i think i might have found one for a sony amp, but it might not be the same)
0 (0.6ms)
pause (0.6ms)
1 (1.2ms)
pause (0.6ms)
0 (0.6ms)
pause (0.6ms)
0 (0.6ms)
pause (0.6ms)
1 (1.2ms)
pause (0.6ms)
0 (0.6ms)
pause (0.6ms)
0 (0.6ms)

Then the device ID, which for an amp, i have found is
0 (0.6ms)
pause (0.6ms)
0 (0.6ms)
pause (0.6ms)
0 (0.6ms)
pause (0.6ms)
0 (0.6ms)
pause (0.6ms)
1 (1.2ms)

. There should then be a pause of (45ms-18ms)--> 27 ms, before repeating the sequence.

I hope you understand all that, sorry if this again seems a bit garbled, but thats how my brain is finding this right now!

Does this look right to you, or am i "way off"? :|
Thanks again in advance,
Ferg

 

[Nigel Goodwin]

Thanks Nigel, that should be quite useful. However (and im probably being stupid), but i cant seem to work out the actual code that is transmitted by the remote for, say volume up.

Try reading my tutorial!.

It gives the main ID codes for Sony equipment (Audio is 16), and the transmitter software lists the Volume up and down codes 18 and 19).

If you build the first tutorial that provides an LCD display that shows the device ID and function code for any received Sony SIRC's signal - just point the original remote at it, and press the button.

 

[fergcu]

Many thanks... must have missed those equates when i was reading through! Will give it a try when all the components arrive, and let you know how i get on.
Thanks again.
Ferg