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[Lcdproc] HD44780 / Backlight flickering solved?

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  • From: peter AT (Peter Marschall)
  • Subject: [Lcdproc] HD44780 / Backlight flickering solved?
  • Date: Thu May 17 13:36:01 2007


On Thursday, 17. May 2007 11:23,
adrian AT
> Firstly, let me just thank the developers for providing socket-based
> access to my LCD display - this is *exactly* what my project requires!
> That said, I have had a couple of problems setting my display up...
> Short Version
> Why does "Backlight=off" in the [server] section of LCDd.conf fix my
> backlight flickering problem? I thought Backlight could only support
> the values "yes" or "no"?

You do not say which version you use, but I guess it is a post.0.5.2 CVS.

But up to 0.5.2 "on", "off" or "open" where only values allowed.
Since then I have allowed more alternatives for "on" and "off".
For consistencies sake, I used the same "values in the docs than for
boolean variables.

To cut it short:
"Backlight=off" is exactly the same as "Backlight=no" in current CVS.

> Despite what I would imagine, "backlight=off" turned the backlight on
> - even through the "thank you for using LCDProc & Linux" message...

No idea about that. You do not tell how you connect your hd44780 to your

> Long Version
> I have tried perhaps every permutation of heartbeat/backlight settings
> in LCDd.conf (after reading that the heartbeat could be causing the
> flickering), and I wondered why "lcdproc -f L" didn't seem to suffer
> from any backlight flickering, while the other "screens" did. However,
> once the CPU usage cranked up, "lcdproc -f L" suffered from the same
> backlight flickering too - it seemed that the problem was related to
> CPU usage?!
Yes, the load screen in the lcdproc client turns on/off backlight
and even starts blinking at some load thresholds.
See the [Load] section in lcdproc.conf on details how to configure it.

Unfortunately this is heavily underdocumented. Any help in adding
documentation is welcome.

> Once I set "backlight=off" in the [server] section of the
> config, I could set DelayMult back to 1, without any problems at all.
> Although everything works now (touch wood) I just wanted to post my
> findings to see if anyone could explain, or benefit from, my
> experiences.

Peter Marschall
peter AT

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