Drive one LCD with two controllers

[jasonlaronde]

Thru another thread we've basically broken things down to this is the only product that will work for my needs...

**broken link removed**

This unit accepts up to 8 inputs to display a pre-programmed message onto an LCD

My project has 16 channels so I've been told to just use two of them side by side...

Being a perfectionist, I figured that would look pretty silly and difficult for the user to understand... (Guitar players will be using this thing)

Is ther any way I could use two controllers and tie both of them to one screen...???

Cheers,
Jay

 

[jasonlaronde]

cebek.com has a couple models that can display up to 14 messages plus 1 default for no inputs and has another model that uses the same 14 terminals in a 7x7 matrix to display 49 messages plus a default but there doesn't seem to be any north american distributers and would cost nearly $300 to get here...

Ideas?

 

[3v0]

It would be more work and money to drive one display from two kits then building a 16 input unit.

A sixteen input version is not a difficult application as applications go.

You could use the kit as a guide to a construct a larger unit with a 40 pin PIC. Then the PIC code needs to be written.

Vellman provides source code for the PC end which could be modified for 16 channels. But you need whatever compiler they are using.

In short it could be done by someone who knows how to do it. But not a great choice for a first time project. If you know how to program it may be possible.

 

[jasonlaronde]

Not a programmer...

As far as I can tell, there's no read to the lcd in this kit, just write... would it not be possible to power the LCD and backlight from one controller and tie the 8 data lines from both controllers to the LCD...???

 

[3v0]

Not a programmer...

As far as I can tell, there's no read to the lcd in this kit, just write... would it not be possible to power the LCD and backlight from one controller and tie the 8 data lines from both controllers to the LCD...???

It would not be quite as simple as hooking the wires together. Maybe a bit of TTL logic.

The LCD is not a simple device. It has codes that initialize it, clear the display that sort of thing.

Both units would be attempting to access the LCD at the same time. You could OR all the inputs from each unit and give the LCD to the one that has the active input. That would work unless the PIC code is reading the busy/done LCD bit.

Actualy you could put the 8 input OR gate on just one units inputs. If it does not have an active input the LCD goes to the other unit. This is done by putting an inverter between the OR gate output and the enables on one units 245s.

Each unit would have a pair of 74xx245 (or similar) chips that gate its signals to the LCD when selected via the output of the OR gate. When not active the unselected units 245's are tristated.

That would allow one unit to init the LCD and then whatever unit is active to display its msg.

You need an 8 input OR gate, 4 74xx245s, and an inverter.

This is a might work solution. I do not like it.