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Topic: 16 X 2 / HD44780 help found if you can't get yours going :-) (Read 1 time) previous topic - next topic

dtp30

Hello All,

I`m sure some one else must have found some LCDs like mine (Or the reason why it happens) Both my 16 X 2 LCDs won't work in 4 Bit mode. But if used in 8 bit mode they work fine! One is a PowerTip , The other is a sharp brand with a real HD44780 chip on board! I just thought it maybe because they are old...

I built my LCD interface off the example off this web page.

Hope this helps some one.  :)

D.



mowcius

Links don't work in your first post.

It is most likely that there was some other issue rather than both LCDs being bad. Perhaps the setup on the webpage is wrong.

floresta

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Hope this helps some one
It would help a lot more if we knew which LCD modules you are using and which software library you are using.  You might try reposting your link as well since there's none showing up in your first post.

Don


floresta

#3
Mar 17, 2011, 03:46 pm Last Edit: Mar 17, 2011, 03:49 pm by floresta Reason: 1
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It is most likely that there was some other issue rather than both LCDs being bad.
There definitely seems to be an issue as this scenario has shown up more than once lately.  My guess, based on very limited information, is that the LiquidCrystal library may not be working reliably with LCD modules that are slower (lower internal clock frequency) than normal.  The 8-bit mode seems more tolerant than the 4-bit mode which doesn't surprise me.  Perhaps a bunch of these marginal or out-of-spec devices just got dumped on the market.

Don

mowcius

Ahh this was discussed - if that is the issue then if you go on the liquidcrystal440 page then there is a version tested on some slower displays.

dtp30


Quote
It is most likely that there was some other issue rather than both LCDs being bad.
There definitely seems to be an issue as this scenario has shown up more than once lately.  My guess, based on very limited information, is that the LiquidCrystal library may not be working reliably with LCD modules that are slower (lower internal clock frequency) than normal.  The 8-bit mode seems more tolerant than the 4-bit mode which doesn't surprise me.  Perhaps a bunch of these marginal or out-of-spec devices just got dumped on the market.

Don


Well i think it is because my displays are so old! One is a PowerTip 1602f, The other is a Sharp LM16A21. It has a real Hit HD44780A00 Driver chip on it. So i thought it would be perfect. All i did was add the extra 4 data lines, Add the referance to the extra 4 lines in the display setup line in the code and they both started working.

I didn't post any links in the first post. As i was talking about this page (arduino.cc). Here is the link on this page. http://arduino.cc/en/Tutorial/LiquidCrystal

My LCD board is a copy of the layout listed on that page. But to get it working i had to use 8 Bit mode.

D.

floresta

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But to get it working i had to use 8 Bit mode.
But it shouldn't be necessary to use the 8-bit mode, if the device works in 8-bit mode then it should also work in 4-bit mode.  

Don

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