[CentOS] USB-serial adapter for CentOS 7

Thu Jul 9 01:12:57 UTC 2020
Kenneth Porter <shiva at sewingwitch.com>

Check the voltages on your adapter. I use such adapters in the machine shop 
so machinists can share the CNC programs they write on a PC with their CNC 
controllers. The CNC controllers can be fussy about voltages, and some 
cheap RS232-USB adapters only generate +/-5vdc. It's within the RS232 spec 
and newer RS232 chips are happy with that, but older systems might want 12v 
or more.

Another issue is handshake lines. Not all adapters provide all the 
handshake lines. Some are "3-wire" data-only with only ground, transmit, 
and receive connected. Some devices will want 5 or 7 wire connections, with 
RTS/CTS and DTR/DSR signals included. Check that the adapter you buy 
provides all the signals your device needs.

Which service are you using to manage your UPS? Nut? Something else? They 
probaby have a mailing list, website, or wiki where you can find out what 
adapters work well with which UPS units. (Be sure to post back here when 
you get an answer.)