Thanks to all those that posted

Mahmood - Yes this is the original source I used in my application (joys of using the search on the left hand side)

once I used the circular buffers (with indexes not pointers) I was then reading the bytes out of the appropropriate buffer synchronously.

I will use Eriks Idea of an idefinite For Loop with a catch inside it to allow me to break out when the buffer is empty as this (seems to me) is the most readable way of doing it.

Regards


Marshall Brown