Hi Richard.
I update my Butterfly Display FirmWare and the FlarmNet database while the display remains installed in the panel.
I use a laptop for updating. It would be hard to find a laptop with serial port.
So, you would need a USB-RS232 dongle (easy and cheap to get). Plus the 3V power supply.
Such a dongle contains exactly the same parts as I am using (USB-TTL bridge + TTL- RS323 converter). The only difference is that I take the 3.3V supply directly out of the USB bridge.

Happy Holidays
3U