RS232-C What's It For?

[MR.MAGOO]

My A/V receiver has a RS232-C port, it is a 'control expansion terminal for custom installation', which would be for what? Owner's manual only says 'see dealer for details'.

 

[markw]

I did a google search on "why RS232C in receivers" and this turned up, along with many other goodies.

http://www.dummies.com/how-to/content/the-rs232-serial-connection.html

 

[fmw]

It is the predecessor to USB, now obselete.

 

[Latent]

The RS-232 serial port on receivers is still in use today by custom installers and home automation setups. It is a very powerful feature but not useful for the average person who only needs to use the IR remote to control their unit. Basically all the functionality of the unit is exposed over the RS-232 interface so that another device or computer can control the AVR. It can set the input or volume or sound mode etc. They could use IR transmitters to do much the same thing but IR codes change between models where RS-232 codes are the same for all units a manufacturer makes. Also IR transmission is not 100% reliable and can fail sometimes. It can also be used by installers to pre-configure a unit without having to go though all the menu's by hand. It was often used when the AVR was hidden away in a cupboard somewhere so that early home automation systems could control audio in multiple room/zones in the house via wall mounted controllers etc.

But things have changed a bit over time now and Ethernet has now replaced the RS-232 port for most of these purposes. Many receivers still keep the same RS-232 communication standard alive in the Ethernet world by exposing the same functionality using a telnet over Ethernet interface. Also much of the computer based configuration that used to go over RS-232 is now available via iOS/Android apps and web interfaces making this more accessible to end users.

Many years ago I played around with it just for fun from my computer hooked up to the AVR with a serial cable just sending basic control codes by hand and watching the receiver magically change modes. But then I never had a real use for it.

 

[highfigh]

It is the predecessor to USB, now obselete.

RS-232 is obsolete? It's used by ALL of the advanced control systems like Crestron, AMX RTi, URC, Control4, OnControls, etc. It eliminates ALL of the problems with IR/RF control. IP control is still young and while most brands haven't brought it to their whole line, they use it extensively. Also, the ability of their control units to control via RS232 will allow them to function equipment that's older, but still operational, like video matrices, DVRs for security cameras, music servers that are too good to toss, etc.

The key in this is CI- most end users don't need to be able to design a system around it but people in the CI industry rely on it.

 

[fmw]

RS-232 is obsolete? It's used by ALL of the advanced control systems like Crestron, AMX RTi, URC, Control4, OnControls, etc. It eliminates ALL of the problems with IR/RF control. IP control is still young and while most brands haven't brought it to their whole line, they use it extensively. Also, the ability of their control units to control via RS232 will allow them to function equipment that's older, but still operational, like video matrices, DVRs for security cameras, music servers that are too good to toss, etc.

The key in this is CI- most end users don't need to be able to design a system around it but people in the CI industry rely on it.

OK, I'll amend my comment to say it is obsolete in both the computer industry and the home audio industry. Some other industries, apparently, haven't caught up.

 

[highfigh]

OK, I'll amend my comment to say it is obsolete in both the computer industry and the home audio industry. Some other industries, apparently, haven't caught up.

How is CI NOT the home audio industry? The main AV manufacturers don't design AVRs for the commercial market. Yes, IP is coming along, but the most common user interfaces are still smart phones, tablets and if they want to, a regular computer. More projectors have an RS232 port than an ethernet port. Oppo and other upper level source devices still use it- it's not going away for a while because it just plain works.

 

[fmw]

How is CI NOT the home audio industry? The main AV manufacturers don't design AVRs for the commercial market. Yes, IP is coming along, but the most common user interfaces are still smart phones, tablets and if they want to, a regular computer. More projectors have an RS232 port than an ethernet port. Oppo and other upper level source devices still use it- it's not going away for a while because it just plain works.

I didn't say it was going away. I said that it is obsolete. So are vinyl records but they are still here.

 

[Latent]

One of the secrets to the longevity of RS-232 in specialized equipment like remote controllable home audio equipment is the simple and cheap implementation. There are no licencing fees or hoops to jump though like USB and Ethernet interfaces and chips and parts to implement the interfaces are very cheap. For PC's the serial interface is indeed pretty much completely obsolete from a consumer point of view now but it still has ongoing uses in certain specialized IT areas.