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Multiple MOI-AL202

Posted: Mon Nov 03, 2008 1:32 pm
by rohman
One of the features of the MOI-AL202 display is the ability to hook up multiple modules with one I2C interface. Does this mean multiple displays can be driven off the same device i.e. computer. The goal is to use these to display specific instructions to associates in a production environment. Each unit would need to display different text at different times and the text would be sent via RS232 using LabView automation software. I would appreciate any assistance you could provide.

Posted: Mon Nov 03, 2008 2:09 pm
by Ray
I2C and RS232 are two fundementally different protocols .A display is either in I2c mode or RS232 you can't use both at the same time or mix them together to get the best of both worlds.

The I2C protocol allows you to address a maximum of 127 devices per bus, although this bus is fairly popular in embedded systems its generally not available on personal computers.

The RS232 procotol allows you to address a single device per port, but the port is usually available on most personal computers. More recent personal computers have been dropping support for this port though.

An alternative would be using an USB display any personal computer should have a bunch of those ports available. You can plug in as many displays as you have ports available and a single cable provides both power and data to the display. So its really easy to hook up.

The USB displays appear on the computer as a virtual comport so labview should have no problem talking to it.

Posted: Mon Nov 03, 2008 2:52 pm
by rohman
Thank you for the quick response.
If I decide to use I2C and purchase an aftermarket USB to I2C bus, does the addressing differentiate witch LCD I am sending information to? Also if I decide to go with a USB display does each display have its own virtual com port, or is there some other addressing method to tell the diferance betweeen displays.

Posted: Mon Nov 03, 2008 3:41 pm
by Ray
Each display will ship with a default i2c address (0x50), so you'll need to program a new adress into the unit once you establish communications with it if you want more then one display on the bus. This is really easy to do, see the manual for exact command.

I do really recommand going for the USB displays though since they will make your life so much easier.

Each display you plug in will be assigned a virtual comport so the first one you plugin will probably be COM3, the next one COM4 etc etc etc.