Sat Jan 18 22:17:02 CET 2020

A single interrupt queue

So, if there are no priorities, it's ok to use a single queue for
interrupts as well.  Make sure they are all at the same hardware
interrupt level, and use an application main loop (bottom half) that

        while read_evt
        external send evt

The interrupt event queue then should have:
- channel (2)
- len (2)
- payload (n)