I'm digging through the manuals of several of the major integrated controllers, such as AMX, Crestron, Ocelot, Homevision, and the like. Why do these guys use an RS-232 computer interface as the primary connection, as opposed to USB, or something a bit newer? AMX makes a $4000 controller, which uses a 30-year-old comm method. Why?
-John O
It's cheap, simple, reliable, well understood, and can be used at distances far greater than is possible with USB. On the manufacturing side, USB adds more cost than RS-232.
Also, most of those you list were designed before USB became ubiquitous.
And you can buy a decent USB to serial adapter for $12.
Do all these guys use the same RS-232 implementation? I recall in the mid-80's when RS-232 as a standard was nearly meaningless...DTE, DCE, 9-pin,
25-pin, and even then some big-company engineers re-arranged it so it was 'better.' I built a lot of cables by hand after reading the pinouts, in those days.A side question...other then a PC for config, what other device would be attached to the serial ports? Do standard cables work for these, or do most installers have to build them...because they'll both be DCE or something? And now I'm thinking...you probably build these every time because of the distance and route of the cable, which makes the RS-232 pinout issue a key skill.
Last Q for now: What is ICSNet? Is this something AMX developed? (my web searching is turning up zeros and lots of AMX-related hits)
Thanks!
-John O
While I'm not intimately familiar with each piece of gear listed, my guess is they all use extremely simplified versions of RS-232. The Ocelot/Leopard uses only 3 wires (RD, TD, & GND) and I suspect most of those you list do the same as the embedded microcontrollers they use have a limited number of pins. Some may also work on 0-5V levels rather than the defined RS-232 voltage levels. Many PCs (especially laptops) also use 0-5V levels on their RS-232 ports. The lower voltages reduce the effective cable length.
The ones I'm familiar with expect to connect to a PC so a standard cable will work. Some may require a null cable but I would expect that to be spelled out in the documentation.
I've never heard of ICSNet. Maybe someone else can help with it. There are several proprietary systems based on RS-485, CAN, etc.
LOL, when I mentioned people messing up the "standard" I forgot about the voltages. Looks like Homevision has a USB, but you have to do serial first to get it set up.
I know that it involves a proprietary protocol, and AMX claims it is for
1000-foot control of all sorts of devices, I'm beginning to suspect it is their own special network.Thanks for your help, Dave.
-John O
Thanks Rod, I appreciate your thoughts.
Usual reason, it takes time for stuff like USB to take over.
Its not surprising that it happens sooner with mice and modems etc.
10/100 Cat 5 makes a lot more sense if you need the distance.
Not really. Have a look at the cost of USB mice now.
Near enough basically.
It wasnt quite that bad.
Yeah, but its not so bad now.
Just other less common stuff now, like radios, smart card programmers etc.
Usually. Not so much with radios tho.
Nope, just use what is supplied.
Nope, they're usually located near the PC controlling them.
Not anymore.
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