Most modern AVRs include at least one hardware USART (or USI in some cases).
Many have multiple instances.
I am trying to determine how often these multiple instances are actually used.
By 'actually used' is meant, in deployed applications.
Yeah I know when you bought that Arduino Mega, you played with all the USARTS, perhaps (as I did) you daisy chained them and measured the over all latency.
That's not a deployed application, but... interesting.
Thanks for your participation!