Re: Do you bother with reading from the LCD (HD44780)?

Jan Panteltje <pNaonStpealmtje@xxxxxxxxx> writes:

On a sunny day (Wed, 06 Feb 2008 16:07:56 +0000) it happened John Devereux
<jdREMOVE@xxxxxxxxxxxxxxxxxx> wrote in
<87ir126pb7.fsf@xxxxxxxxxxxxxxxxxxxxxxx>:

Jan Panteltje <pNaonStpealmtje@xxxxxxxxx> writes:

On a sunny day (Wed, 06 Feb 2008 15:50:43 GMT) it happened _
<jtayNOSPAMlor@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
<kq6zmfxp8mtn.1eqsnpqll5mri.dlg@xxxxxxxxxx>:

I have an extra pin; the R/W pin of the LCD is tied low so output always
works - but I could use that pin to control the line.

Does anyone read from the LCD; and if so, why?

You make a mistake, you need to *read* to check the 'busy flag'.

You don't *have* to - you could assume a "worst case" timing
instead. I used to do this, it means the program can still carry on
even if there is no LCD working. (Without needing timeouts on every
operation). Text output is usually so slow the extra delay does not
matter.

That depends, if you are on RS232 and a small buffer (say 3 characters),
you will be more limited in baudrate if you use a fixed delay.
Your delay will have to accomodate worst case parameters, and be long.

Sure, it's not always a good idea.

When I did it I had a separate task for the user interface and the
serial comms. An extra ms will make no difference in the UI task, and
could save a pin and some complexity.

And I do not see how you can select a line in a 4 line display with one bit.

Sorry, don't know what you mean here.

--

John Devereux
.

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