LCD R/W pin, is this needed?

[Will Reeve]

I am running out of pins; I am using a LCD 4-bit parallel interface, as I only ever write to the LCD I can’t see any problem in tying R/W to GND via 10k. My code allyways holds it low anyway. Anyone else do this?

I remember one problem on an old design with initialising a certain brand of LCDs where you had to wait for conformation of the init settings, but the batch I have here (5 examples) of a new type seem very happy indeed with the “delay” method of init. I just don't want the next batch to need it!

Will

[alexbilo]

I've used this trick before... Never had any problem with the LCDs I used. Of course, that doesn't guarantee that you'll never encounter LCD that needs some reads, but I guess you'll be able to find models that are compatible with your design.

Good luck,
_________________
Alex

[rnielsen]

You are 'supposed' to check the Busy Flag(BF) every time you write to the LCD or you might get garbage on the screen. The only way to do this is to put the device in Read mode so you can check that bit. I used to simply put a delay in my routine but found that the display would 'wigg out' every now and then. Since I started checking the BF bit I haven't had any problems.

Ronald

[Steve H.]

I don't use this pin - I add in the worst case delay and always wait that amount of time - instead of checking the busy flag. I have done this for nine years with VFD's and LCD's with no problems.

Steve H.

[Mark]

The proper way is to check the busy flag. However, some people still put delays after writing to external serial eeproms rather than checking for an ACK. Obviously checking the flag is better and doesn't waste processor time on a delay.

[Ttelmah]