falcon74:
@fungus, are you suggesting that I hook-up the TTL-level Tx pin, to the dongle/converter's RS-232 level Rx pin, and "try it out" ? Nothing bad can happen, because Rx-end can, in worst case expect higher voltage signals (and perhaps, also inversion). At worst, this thing won't work, but usually no fear of magic-smoke! Right ? Or, I didn't understand your last statement.
Yep. I don't see how anything bad can happen if you only connect that wire.
PS: Connect GND as well!