ATtiny45 with arduino

Why not use  I2C for your communication between the two microprocessors?

This link might be helpful.

That is verry interesting and i will definitely look at it , but with the time i have i wont be able to study it and complete my other project in time ,

I , however just came up with another simple idea to use one digital PWM pin to send different values to the analog input of the Attiny

Heres a visual example :

It wont be with a geat accuracy but i only need 3 values and i think thats achievable

Plus with this i dont need filters and stuff

What do you guys think, it has to work.(I am still waiting for the attiny to arrive and i cant test it...)

And thank you all for the suggestions

If your going to do that then why not use an IR emitter and receiver.

The code is much simpler, at least for me, Im not sure what the code will look like for the IR emitter and receiver.And what is the difference?I mean im not fully familiar with the IR stuff

for the IR side, you can consider the H/ware as a Gate, light comes on, resistance drops.

that`s a single binary state, so you need some sort of protocol to get more than one state out of it, else you could just use 2 (or 3) pins to a 74138 and get your 4 (or 8) switch states from that.

you could write your own protocol, a bit like Morse code for just your 3 switches, or use a Library that will also parse single line coms like I2C, Serial, IR, or even a Morse code look-up table!

the problem is more likely to be Which of these has a greater Memory economy?

and so it becomes a Sizing excersise more than anything at this point, as All of the above will actually work, just how much Mem is left over for you to use?

you could even go the RF route, with these TTL 433MHz transmitter/receivers (they`re only tiny!).

for the IR side, you can consider the H/ware as a Gate, light comes on, resistance drops.

that`s a single binary state, so you need some sort of protocol to get more than one state out of it, else you could just use 2 (or 3) pins to a 74138 and get your 4 (or 8) switch states from that.

you could write your own protocol, a bit like Morse code for just your 3 switches, or use a Library that will also parse single line coms like I2C, Serial, IR, or even a Morse code look-up table!

the problem is more likely to be Which of these has a greater Memory economy?

and so it becomes a Sizing excersise more than anything at this point, as All of the above will actually work, just how much Mem is left over for you to use?

you could even go the RF route, with these TTL 433MHz transmitter/receivers (they`re only tiny!).

Memory is an issue couse i do have alot of writing to do , and i dont need that much resolution.

What I mean is that I can set that LED to a value of 85, 170,255 and the LDR will be set to 3 sectors -the first one - >10 <130; second - >130, <200, 3rd sector- >200, And that will set one of three pins on the ATtiny HIGH.

Im not familiar with how to set frequency and other stuff on that IR led YET...so i guess that will have to do