Hi Shel,

> >> Is it necessary to pull the unused inputs to the lcd low externally ?
> >
> >  Yes.
>
> Are you sure about that?  My interface _appears_ to be working fine, yet I
> leave the four extra data lines DB<3:0> floating.  Am I likely to blow them
> up or something?  The example code from Optrex, for 4-bit interface, doesn't
>  _use_ DB<3:0>

As Peter Tiang  mentioned they have pullups.  Having checked the data sheet
the only difference will be the mode that the display will be in
while you are setting it up for 4 bit mode, this intemediate mode
gets squashed by the 4 bit mode select command so it looks like it
won't matter which way you leave the low bits.  Letting them float will
consume a few microamps less perhaps.  Pulling them to ground will
prevent ESD from creeping into your display.

I ground them myself and it has always worked.

Cheers     *<<<-|
--
Kalle Pihlajasaari   kalle@ip.co.za   http://www.ip.co.za/ip
Interface Products   P O Box 15775, DOORNFONTEIN, 2028, South Africa
+ 27 (11) 402-7750   Fax: 402-7751    http://www.ip.co.za/people/kalle