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Valued Contributor III
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black bar on the lcd

hello all! 

 

i am using the nios ii dev kit stratix ii edition.  

and i tried fiddling around a bit with the lcd a bit. just writing some random bits to lcd_e, lcd_rs, lcd_rw and lcd. 

 

unfortunately, my experiments resulted in a black bar on the first line.  

at first i thought this problem would go away by turning it off and on again. 

 

it didn't.  

and since i did not know exactly what i did, i cannot undo it. 

 

 

does anyone know how to reset the display?
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Valued Contributor III
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I don't think there is any persistent memory in the LCD, so I don't see how you could have set it in a permanent mode that survives power loss... Are you sure you turned it off for a long enough time?

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Valued Contributor III
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i think 12 hours should have been more than enough...

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Valued Contributor III
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dettus, 

 

 

--- Quote Start ---  

and i tried fiddling around a bit with the lcd a bit. just writing some random bits to lcd_e, lcd_rs, lcd_rw and lcd. 

 

unfortunately, my experiments resulted in a black bar on the first line.  

--- Quote End ---  

 

 

It could be that your lcd did not survive the "random bits". You can read from and write to the internal registers of the lcd. I do not know the specific board schematic and lcd that you are using. But if both your fpga and your lcd are forcing incompatible data on the databus, it could be that your lcd controller I/O has been burned down...  

When you read from the lcd your fpga pins should best be set to the high impedance state.
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Valued Contributor III
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Hi, 

 

The black bar on the first row of the LCD is due to a wrong initialization process, typically caused by timing violations, but it is very hard (practically impossible) to break the LCD controller just by playing with the bits. Did it work OK at any time? 

 

If it did never work, take into account that the LCD is EXTREMELY slow, so check if your system is providing it a right clock frequency and also check if you are doing a correct initialization sequence (see the datasheet). 

 

See you!
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Valued Contributor III
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yeah, when i got the board it worked.  

everytime i switched on the dev kit, there was already a little demo in the factory config. 

 

the lcd was used to show me the ip-address it got over the ethernet port so i could connect to the webserver. 

 

but even with this demo app, it still shows me the black bar of death. so far i assumed that it already has the correct initialization sequence?
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Valued Contributor III
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In that case, yes, it looks like it is fried... 

You should be able to change it, it is quite standard and not so expensive.
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Valued Contributor III
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Hi, 

 

Well, in that case it may be broken, but before changing it I would try one more thing. You know that the code executed when you switch on the board is stored in a EEPROM memory in order to maintain it even when there is no power. Have you tried to reprogram the default memory content? It is possible that at some point the default code had been overwritten or damaged in some way. Try to reload the ".pof" file (".pof" is programmable into EEPROM while ".sof" just only into RAM), which should be included in the board documentation, and check if the problem persists. If so, then the LCD may be broken definitely and you will probably have to change it (it is so easy, do not worry). 

 

See you!
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