'Non-Deterministic' memory usage on Arduino I had a problem with a memory leak in my sketch and cornered it with MemoryFree.h. This works great and I was able to fix my leak.

My sketch is not really static, but My var sizes are. I observed, that the free memory on the arduino reaches a different values and stays there. 

For Example


Run 1: 1655 Bytes Free
Run 2: 1659 Bytes Free
Run 3: 1654 Bytes Free


For every run, I get a different, but over a short time, fixed memory usage. Is this normal? 

P.S: The serial input to the script just repeats forever with the exact same data.
You haven't posted any code, so any answer is guesswork. However ... if your code makes decisions based on external events (eg. readings from sensors) then it may allocate memory differently, and in a different order, each time.

Sometimes memory allocation leaves gaps (known as "heap fragmentation"). Small differences in your results probably show slightly different sized gaps, due to the allocation order.