rdtech-tc: detect receive and parse errors, terminate acquisition

rdtech-tc: detect receive and parse errors, terminate acquisition

Pepper the code paths from main loop calls via serial reception to
data processing with return code checks and error handling. Terminate
acquisition when communication or data processing fail.

Check whether acquisition limits were reached immediately after more
values were submitted. Keep a periodic check in the main loop call to
handle duration limits.

Comment on essential steps in the execution sequence.