jasonlaronde said:
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.