We needed a 2.5V UART to RS232 Adapter for a development project. I was unable to find anything lower than 3.3V available on Amazon/Digikey/Mouser, and rather than use a level shifter I opted to create my own.
I used one half of a MAX3316 transiever. Datasheet
I have built 4 of these boards so far and have verified that they function at 115200 baud.
In the future I would like to push the limits of the baud rate, and I would like to verify the RS232/UART signal integrety. Before making additional boards, I would like to add a 2x3 2.54mm connector so the RS232 TX/RX can be switched with jumpers. This would eliminate the possible need of a null modem cable.