@ruijc

I have added examples that use SerOut2 and SerIn2 but I have not tested these as I'm rather busy with a project of my own right now. They should be easier to follow.

The problem with using $55 or $AA (or a string of several) is that the receiver has difficulty distinguishing them from the normal noise it sees in the absence of a signal. Using a long pulse followed by a space (about half the length of the pulse) sets the receiver AGC and gives the receiver an easy to distinguish marker for the start of a transmission. Keeping communications packets short will help maintain DC balance