Thank you for your comment Vanepp 
In fact, I wanted to ask for FaizanHamayum to post the datasheet of LS2811, but after re-read his post I have found the answer to my question.
And I agree with you, a smaller µC would be enough.
I suggest you to have a look at ATtiny chips. They have a analog to digital converter and they are smaller than a 328.