Is there a TTL-to-RS232 Level Shifter that allows me to select the output either TTL or RS232

Thread Starter


Joined Feb 8, 2022
Hi everyone,

I am looking for a TTL-to-selectable-TTL-or-RS232 level converter IC. Essentially, my host outputs UART TTL, but the UART client can expect either TTL or RS-232. I cannot find a TTL-to-RS232 level shifter that has an enable pin allowing me to select the output is TTL or RS232.

Thank you for your advice!

Thread Starter


Joined Feb 8, 2022
MAX232 IC.
Thank you for the suggestion. I went over the datasheet of MAX3223 since I am using a 3.3V microcontroller. If I feed the UART TTL to the TTL/CMOS INPUTs, the MAX3223 IC will output both:
TTL out (looks like this output TTL will be inverted signal from the input TTL?​
RS232 signal​
Am I understanding this correctly?


Joined Jan 27, 2019
Why would you want to select TTL on a TTL to RS233 converter?
If you want TTL then toss out the converter.
I think the TS would like a "passthrough" mode so the level shifting could be turned on and off without the complication of bypassing using external components.

[EDIT: reworded]
Last edited:


Joined Feb 20, 2016
Having the levels selectable could be a recipe for disaster.
I can just see the RS232 levels sent into a TTL input and damaging it.
A good idea is to have different connectors for TTL and RS232 to avoid that.
I agree with @MrChips in post #6.
I cannot really see a problem, just add the converter when needed.