What are you connecting your CP4 RS-232 directly to? What other external devices have RS-232 ports? WhySome things:
* GTOCP4/5 has Ethernet, WiFi, USB, and RS232 ports.
* USB is known to have reliability issues.
* USB cables are limited to 15 feet without active extenders.
* USB plugs are not physically very secure. That is, they are easy to get pulled out especially with only 15 feet of cord.
* Many customers are still using RS232 ports, so getting rid of them would not be wise.
* You can still get computers with built-in RS232 ports and add in cards are cheap and very reliable.
* You can run serial cables several hundred feet.
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver