Basic hardware questions about 16x2 LCD with 4-bit data usage

[linkstatic]

What i wanted to ask is simple. If i am using a 16x2 LCD and using 4-bit Data ,not 8 -bit, is it necessary to ground the other 4 pins which are unused? If there is a 15 and 16 pin on the LCD do i need to use it too? what if i leave the D0-D3, pin 15 and pin 16 open without grounding them?

If my proteus successfully runs the LCD in the simulation is it 100% that the circuit will work in real world?

 

[alexan_e]

the usual way of using the 4 bit mode is to ground the unused data pins to make sure that they have a value of 0.
I think there was a thread a while back and someone said it worked fine without ground but I haven't seen anyone else recommend this way.
The proteus model is not as the real one, for example it works without supply or contrast.

Alex

 

[wp100]

Hi,

Have found leaving d0-3 disconnected does not cause any problems, though its generally suggested to tie them up or down.

If you want to use software that uses just 2 control lines E and RS, RW must be tied to ground on the lcd.

Pin 15 and 16 is for the led backilght, if fitted on your model, again they can be left unused .

If you do use the backilight it typically operates at 4.2v maximum so a dropper resistor is needed or a simple variable supply like a lm317 is you want to make it adjustable.

If your code works ok in ISIS then it will more than likely work on a lcd, provided you take care in wiring it up, its easy to short those pins when soldering.

You might find this tutorial informative for hardware and software.

http://www.epemag.wimborne.co.uk/resources.htm

 

[Kurenai_ryu]

mmmm i don't like the idea of grounding them, as many lcd libraries in the web 'READS' the status byte, and while reading the data pins obviously they become outputs... mmm sending an output to ground... higher current consume...

now, also, don't forget that while initializing the LCD it's still 8-bit wide and these reads uses all the data pins... I'm not sure how it behaves once it's configured for 4-bit wide bus, but better to be save and leave them disconnected (or correctly, connected to ground with a pull-down resistor of 4k7 ~ 10K ohm)

of course if your LCD library relies on delays for data output (generally the RW is tied to ground) it's OK to ground the unused data pins...

 

[linkstatic]

Thank you alexan_e, wp100 and Kurenai_ryu for your inputs much appreciated