KC868-A6 Digital input IRQ

[Libramale]

there is a extend serial port on KC868-A6 board. the free GPIO is GPIO12 and GPIO13, you can use for PCF8574's nINT pin.

Thanks for the response. Your suggestion raised a couple of additional questions.

Q1. Where physically on the PCB would be best and safest place to solder strap wire to U3 PCF8574P nINT (pin 13) signal?
Q2. We need to use the spare UART/serial port for communicating to an external device. Is it possible to either of the RS232 pins for an IRQ signal?
Q3. If so, which of IO16/17 would be most suitable being floating and not pulled up or down by the SP3232EEN chip?
Q4. If so, where physically on the PCB would best and safest to solder the strap wire for using IO16/17?

For best/safest PCB solder locations can you please indicate on PCB, top or bottom, with an arrow.

Thanks again