Locating unit some distance outside PC

meep · Post by **meep** » Tue Mar 23, 2004 11:15 am

Hi All

I have a mad project in mind!

I want to build some wall-mount units in various rooms around my house to control a whole house audio system based around my PC. (multiple Winamp instances pumping MP3s out through a multi-channel sound card).

The idea would be to pop a MO unit in a box and wire up some controller keys to the matrix.

Anyway, I already have CAT5 cable runs from my PC to the wall mount points.

My basic question is, what's the best way to get data and power to a MO LCD located some distance from the PC with CAT5 as the carrier.

My first inclunation is to use some from of USB/CAT5 convertor but will this set-up carry power?

Do the USB units receive power over the USB cable? (no messy Floppy cable conversion etc.)

Any thoughts on the above appreciated. Anyone done it already? Anyone got any pointers to DIY websites where this kind of thing has been done?

Cheers

Peter

Miles · Post by **Miles** » Tue Mar 23, 2004 4:04 pm

What type of display are you thinking of using in this "interesting" project??

meep · Post by **meep** » Wed Mar 24, 2004 2:21 am

Hi Miles

I'm open to suggestions. Essentially a 2 or 4 line character display.

What will be easiest to communicate with over distance?

If USB units can derive power from the USB bus then they will most likely be most suitable. I'm looking at significant distnaces from the PC to the unit so I don't think it's the type that's the real issues, it's getting the communications and power signals to the unit over CAT 5.

Thanks for any assistance that can be offered.

Peter

Miles · Post by **Miles** » Wed Mar 24, 2004 10:10 am

The only reason I ask if because the serial cable can be various lengths, mostly dependent on how well insulated the cable is, the thickness of the wires, what speed you will be communicating at, and how much background noise there is. At 19.2kBps the maximum safe distance is 50-200ft. At 9600Bps it is between 250-500ft. Unfortunately the USB specification is only 16 feet. This is due to the propogation delay and reflection.

meep · Post by **meep** » Wed Mar 24, 2004 10:21 am

OK

So it looks like serial is the way to go. I'm comfortable with that as I already have a serial MO unit in my HTPC which I control via Girder.

Now, what about getting +5V and Gnd over CAT 5. Viable?

Also, I'll obviously need serial expansion on the PC side to allow more than one 'zone". Would a USB-Serial convertot be suitable giving me up to 4 serial ports on one usb channel?

Thanks for all the insight.

Peter

Miles · Post by **Miles** » Wed Mar 24, 2004 10:41 am

You could use +5V, Signal, Grnd on a CAT5 cable however I would advise doubling up your power and ground lines. Since your best solution is using serial LCD's, you must connect each one seperately or you'll have no way of distinguishing between them from port to port.

Dormouse · Post by **Dormouse** » Sun Jun 06, 2004 6:41 pm

I've got a related question... it looks like I need to run a serial connection through a CAT5 cable too, but I'm wondering which lines in the serial port are actually needed by the LCD because of course CAT5 only has 8 wires and RS232 uses 9. I'm already using two wires in the CAT5 for GND and +5V, and three for other things. That leaves 3... is that enough? I'm guessing that I only need two: RxD and TxD. Does that sound right?

p.s. I'm using a GLK24064-25, just in case that matters.

Miles · Post by **Miles** » Mon Jun 07, 2004 9:43 am

How are you powering the module? Are you also using the CAT5 to do this??

Dormouse · Post by **Dormouse** » Mon Jun 07, 2004 10:21 am

Yup. My wording wasn't very clear... the GND/5V lines in the CAT5 are for powering the display. I saw your suggestion about doubling the power & ground lines, but it looks like I'm not going to have enough wires to do that and anyway I'm hoping I won't have to if the problems I'm seeing are in fact due to flow control. (And so far, it seems that maybe they are.) It seems that the pl2303 USB serial adapter Linux driver may not support flow control even though the hardware does :-(. Still investigating that though.

Miles · Post by **Miles** » Mon Jun 07, 2004 11:06 am

Rx and Tx lines will be all that you need in this case...We actually don't use flow control like you would normally think. All our flow control is internal and no "hardware" is needed. When using our devices with flow control it's best that the flow control is initiated and controlled by our devices only.