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[Lcdproc] Re: HD44780 / Backlight flickering solved?

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  • From: adrian AT (Adrian Hardy)
  • Subject: [Lcdproc] Re: HD44780 / Backlight flickering solved?
  • Date: Thu May 17 13:57:01 2007

I realised after posting I had missed out some pretty basic details...

> On Thursday, 17. May 2007 11:23,
> adrian AT
> wrote:
>> <snip>
>> 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.
It was the nightly tarball, downloaded yesterday evening (16th May)

> 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.
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.

>> 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.

>> <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!

I will continue testing, but at least now I can always resort to a
"stable" configuration.


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