Re: [lcd4linux] 3x HD44780 problem / special character problem

[Kamil W. <we...@ra...>]

Hi Michael,

>> Then I got high-spirited and tried to wire up a third 20x4 HD
>> compatible LCD. In order to do so I salvaged the the third enable
>> line (EN3) by disconnecting R/W from the 40x4 ( and connecting that
>> to GND ). The 40x4 share the RS line,
> all three displays should share the RS line!

Yes, they should, but since it is a 40x4 and therefore it has two controllers on one
board I presume they share the RS line anyways. There is no second RS pin on the
connection bracket.

> You can omit the 'size' parameter (IIRC) because LCD4Linux automatically
>  sums up the individual sizes.

Thanks for the advice, at least it saves up a config line.


>> Wire { RS          'INIT' RW          'GND' ENABLE      'STROBE' 
>> ENABLE2     'SLCTIN' ENABLE3    'AUTOFD' BACKLIGHT   'GND' GPO
>> 'GND' POWER       'GND'
>>
>> } }
>>
>> Is this correct, theoretically ?
> Looks very correct to me. Although I must say that I've never used more
> than one display... geronet?

Stefan ( geronet ) already picked up the issue but he has no further advice
other than to look what's happening with an osci. While I have a 60MHz
osci ( which should be sufficient ) I am not that familiar with the protocol
and timings so I don't really know what to look for. Any advice here ?

>> I believe so, but the practical result proves me wrong. The 20x4
>> won't even intialize. I only see two lines of blocks. I can't be
>> completely sure, that the 20x4 display isn't broken since it isn't
>> new but an older one salvaged from a display project some time ago.

> Yopu got two lines of blocks? Normally there should be only one (or line
> 1 & 3 on a 4-line display). This is how the display tells you "I'm ready
> for being initialized".

Right, that's what I figured. Since it is a 40x4 lines 1&3 are filled with
blocks. That issue got solved once I bought a new 20x4. Both Display
initialize correctly now, but th 20x4 only shows garbage and the lines 5-8
which are supposed to be shown on the 20x4 are shown on line 1-4 above
the original 1-4 definituin. I have taken pictures but I was hesitant to post
into the ML because of traffic issues.


> Maybe it's a contrast problem? There are displays out there which have a
> good contrast with the contrast hardwired to GND; but others really
> require a resistor (or better a potentiometer). This would explain the
> two black bars, too.

That's not the problem.

>> Since I sit in Germany and I like our °C trailing any temp degree
>> value I wanted to add a postfix to get something like CPU: 34°C.
>> After doing so my whole layout got screwed up. I searched the
>> archives and found something about using \337 the octal value of the
>> ASCII character, but that didn't work out as well.
> 
> Are you sure that your display has the degree char has 0337? I think the
> octal stuff should work, although I'm not sure (I'm in the office at the
> moment, and therefore cannot test). You could try any other ASCII value
> (maybe just an 'a') just to make sure this works...
> 

Here is a link to the datasheet, but I'm afraid that ASCII definitions are not
covered :

http://www.anag-vision.com/avkat/av4040.pdf

However, when the Display shows garbage he flicks some weird ASCII characters
through it and I could clearly identify the ° sometimes. So I *guess* the Display
is able to produce it when properly triggered. Is there any other way to tell the display
what to show ?

> bye, Michael
> 

Thanks a lot, Kamil