Nov-05-2018, 11:04 AM
Quote:Don't they communicate fine without?Yes, they will communicate just fine if all variables are set properly.
There are obscure things about RS-232 that are hardly ever used, but once in a while you will run into them.
Some of these include use of secondary CTS, DTR or DSR being used, Cable reversing CTS and RTS and/or (usually and) CTS and RTS reversed in cable.
Use of putty (or some other terminal program) will show these immediately, and can be modified immediately just to get the proper setup.
As stated, this is rarely the case, but is does happen, and the first time it does, the value of using a terminal program becomes apparent.
When I first started using serial communications we didn't have putty, nor did we have USB. It was imperative back then to use a 'break-out' box to check connections. Old habits, it's sort of like checking your gasoline before takeoff.