Keeping time without RTC

I'm interested in keeping time accurately (relatively, nothing amazing) but I don't need to actually set/recall the time. I just need to keep a stepper motor rotating at the right speed. I want to use a micro controller for this because its not a simple 1 hour/1 rotation sort of thing, I need to do some calculating to ensure that little errors in difference between steps and time are kept accounted for.

My only time keeping experience has been with the DS1307, and I like it, but I figure I could simplify. Additionally I would like to use an ATTiny85 which I'm afraid my lack of experience will cause problems with using atmega328 libraries and I2C.

Just looking for suggestions for now... Thanks

An RTC like the DS1307 will be no more accurate than the Arduino itself (as long as you use an Arduino with a crystal).

So you can use the millis() function to keep track of time to a few parts per million.

If you use an 85 with no crystal though it will not be very accurate.

I need to do some calculating to ensure that little errors in difference between steps and time are kept accounted for.

Can you elaborate? Just how accurate do you have to be?


Rob