this script reads out all relevant data from the connected terminals
such that it can be used for offline tests. Also add the retrieved data.

if the status of the bus is unknown, we need to assure not
to address two terminals at the same time

This adds support to actually use the SDO data from terminals, and also add useful command line tools to inspect the bus.

See merge request teichman/ebpfcat!6

Beckhoff calls the input sync manager number 3, the output one
number 2. It's weird, but let's follow the standard.

This means we can access variables directly from user space, we do not need explicit reads or writes.

See merge request teichman/ebpfcat!5

bus couplers seem to be incomplete

that's what I found in the EEE lab and Brad's box

See merge request !4

and other improvements

See merge request teichman/ebpfcat!3

this is for debugging

this doubles the number of packages in the loop, but is an
effective measure against package loss

not very well tested, but a step in the right direction, I hope

not so great, though

addresses in memory look like 32 bit values but are actually 64 bit