Do you really need all of the sigals for a general RS-232 port

interfacemodemrs232serialtransceiver

I know that having TX, RX, GND, RTS, CTS are good. What about all of the others? Do devices these days even make use of the other pins (DSR, RI, DCD, DTR)? Is it safe to generally leave out these pins? It seems to me like these are mostly only used in fully-specified legacy DCE/DTE equipment. FYI I'm asking this question more specifically in the realm of embedded systems, not PCs.

Best Answer

Yes. Actually, a lot of RS-232 applications don't even use RTS/CTS anymore and have no hardware flow control at all - it is all done in software. Especially with the advent of virtual serial ports this is more the rule than the exception.

However, if you want to make a general RS-232 interface, RTS/CTS is smart to leave on there, just in case you are planning to attach a peripheral that uses it.