In my present application, I was able to borrow a single pin on the ATTiny85 in order to send out debugging information. This article describes the software that runs inside the ATTiny85 plus software that runs on a companion Pro Micro. Together they let me send bytes out this single pin and have them show up on my laptop.
For those of you with far more experience programming Arduinos, I welcome suggestions on how to make the code on the ATTiny85 smaller and use less real time. I would also like to speed up the throughput of the Pro Micro.
If you are interested, please see
Your comments are welcome. All of us are smarter than any one of us.