Sure, Circular/ring buffer. I understand that part. But if I send it to the serial port in loop, I have to disable interrupts for each byte sent. Otherwise the ISR will interrupt the serial routine. If I send more than one byte, the interrupts will be disabled for too long and I'll miss a Mic sample. So I have to send one byte at a time then check for (enable) interrupts to sample the Mic. If that's the deal, why not just send 1 byte at a time within the ISR? My first experiment will be simple, the byte I just got. Then add the ring buffer.
Can I send 1 byte from within the Mic sampling ISR? There is no delay, assuming the buffer is empty.