(2020-12-01, 02:25 AM)CapnKernel Wrote: I think holding one line at ground, and sending 5V on the other will be fine:
https://www.electronics-notes.com/articl...torial.php
Your calculations I trust, but don't mistake mark for space: "A space is represented by a line voltage level in the band between +2 and +6 volts while a mark is represented by a voltage in the range -2 to -6 volts". That's what I meant when I said inverted: with ttl, a mark is electrically encoded as a positive voltage; at rs232, a mark is negative voltage.