To program the attiny85 you can use the arduino uno as isp programmer. You can look this link (http://hlt.media.mit.edu/?p=1706
) for more information about this procces, but you dont need to because im gonna explain everything in detail.
I use a attiny because is cheaper than use an arduino. you can buy a attiny85 for 2.84USD, compare to an arduino for about 38 dolars. Using an attiny to comunicate through a rf link represent a chalenge because the attiny doesn't have a rx or tx serial comunication by default. I want to thanks this blog (http://mchr3k-arduino.blogspot.mx/
) for make the program that make possible to comunicate with an attiny.
ok. so let go to step by step programing.
1. go to the arduino oficial site and download the arduino-0022 software. (don't use the arduino 1.0, it doesn't work). Unzip the file. you should see a folder name arduino-0022.
2. go to this link.http://mchr3k-arduino.blogspot.mx/2012/01/wireless-sensor-node-part-2.html?showComment=1338749638806#c853067277980266192
download the attiny45_85.zip
and the manchester.zip
3. Unzip the attiny45_85.zip file. copy the folder.
open the arduino-0022 folder. Open hardware
and paste the attiny45_85 folder there.
4.Unzip the manchester.zip file. open that manchester folder and you should see two other folders. core and MANCHESTER.
copy de MANCHESTER folder.
open again the arduino-0022 folder. but this time open the libraries
folder. paste the MANCHESTER folder there.
Now you have the software ready to program.
5. launch the arduino-0022 program. click in the arrow poining up (open) and open the ArduinoISP example. click in tools>board>arduino uno. (look you now have all the attiny in there).
Upload the program.
6. Place the attiny85 in a protoboard (breadboard), and connect everythingh to the arduino as the image. Be shure you place the attiny in the correct way or you are going to burn it. (happened to me :P) .
7. On the arduino program go to tools>board>attiny85 (w/ Arduino as ISP). click again tools>burn bootloader>w/ Arduino as ISP. (you may see a error but that's ok).
ok, So let's make the program for the transmitter.