2 x LCD screens, can I just wire them in parrallel?

[D n T]

I ned to sit down and get all breadboarded but i would like to run two LCD on the same unit, example one for the driver and one for the tech at the back, they are both displaying the same data atc, can I parrallel wire them and do I have to put diodes in to the signal, RS etc pins to stop one panel effecting the other?

There will be a third LCD panel assosiated with this application, back at the pits to allow real time monitoring of the vehicle. The information will be relayed with a 433mhz radio link.
I just like the idea of being able to do that.

 

[Tom2000]

With HD4478 interfaces, and with R/W* grounded for both displays, I think that all data lines would be configured as inputs, so paralleling should be OK.

However, I'm not sure how they initialize at power up. You might need diodes on one display to guard against the data or control leads being initialized as outputs, with one high and one low.

Please let us know what you find when you breadboard this arrangement.

Thanks!

Tom

 

[hippy]

I agree with Tom2000, it should be okay to just wire them in parallel when they are write-only devices, but that's unproven.

You could put 1K's in each of the LCD data and control lines and then common them at the PICAXE output pins. That should mitigate any potential problems. I think this is one of those situations where the best answer you'll get is from trying it. It is always worthwhile checking if there are any obvious reasons it would not work but I don't see there are.

 

[D n T]

Double decker LCD

A PICAXE 28X( thats what I'm using, althought an 18 would work too) runs two 16 x 2 LCD screens, no problems.
I wired up and programmed a single 16 x 2 LCD screen according to Hippys method, no problems, of course.
I set up the bread board so that the first LCD was mounted on the right hand side of the group, it worked as per normal.
I soldered a ribbon cable to an LCD and the other end to pins, including the backlight pins ( 15, 16), and plugged it in to the row next to the first LCD pins, applied power, it all worked including initialisation and data display. Perfectly mirrored.
No diodes or resistors, although I will be using them in the next evolution of the circuit.
By the way, the LCD displays an ADC derived from an ACS750, and that works fine.
Anyone for three screens

 

[eclectic]

Thanks for the idea.

DnT. Thanks for the original question.
Tom and Hippy :- thanks for the reassurances.

I've just tried wiring two serial LCD's to one pin of an 18X.

2 x AXE033 or 1 AXE033 + 1 firmware wired display.

No blue smoke here either.

e.