I have two signal lines that I will be monitoring with an MCU Input I/O pin (3.3v powered). Both inputs will be coming from external sources. I will be monitoring each of them for a high or low state. The problem is that the signal coming in could be between 0v and 24v, and the signals coming in "may" be serial data (approx 9600 baud).
Below is using something like the BAT54SWT1G Schotch Diode Array to clamp voltages at 0v and 3v.
EDIT: Updated schematic with a current limiting resistor before the clamping diodes.
Schematic was redrawn in conventional orientation by Transistor