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[Lcdproc] Re: HD44780 / Backlight flickering solved?

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  • From: peter AT (Peter Marschall)
  • Subject: [Lcdproc] Re: HD44780 / Backlight flickering solved?
  • Date: Thu May 17 17:11:02 2007


On Thursday, 17. May 2007 15:52, Adrian Hardy wrote:
> That's very interesting - I'm absolutely positive I tried
> "Backlight=no", with little success. Would the position of
> "Backlight=no" in the config file affect the behaviour? I moved it from
> the driver section to the [server] section. I will try out more
> permutations tonight to try and find the cause/solution.

Of course, it affects the behaviour.
That's what sections are for.

Config directives are always relative to their section.
If a specific config directive is not specified within a section,
the built-in default value of that config directive will be used.

It does not matter at all whether other sections
contain directives with the same name.

Instead of trying permutations you might have a look at the code.
Lcdproc is open source after all.

> >> 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
> > system
> Sorry about that - that's quite an omission! It's connected via the
> parallel port using "winamp" style wiring. While struggling to come up
> with a successful configuration, the "thank you" message was never
> backlit, but with backlight=off, it is lit!.... which is strange.

Sorry, I have no information about displays on the parallel port,
since I do not own one myself.

A few hints:
- Did you check the wiring with the one in the LCDproc docs ?
- Did you check out

> >> <snip> ... "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.
> Aha! My test platform is an old P3 600 Mhz laptop (the only machine in
> the house with a parallel port!), and the run queue regularly sits at
> 1.0 when gnome is running. If the backlight switches on and off in
> response to a high load on the [Load] screen, then my findings were a
> bit of a red herring!

you may change the thresholds for lcdproc's load screen in the
[Load] section of lcdproc.conf.
E.g. setting them to
should disable blinking and turning the backlight off.


Peter Marschall
peter AT

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