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Forum: FPGA, VHDL & Verilog Display Values on 20x4 LCD


von JOSE P. (josepicollo)


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Hi dears.

I'm dev. a digital relay using an Altera FPGA, with Nios II support. 
But, I have an issue to use the 20x4 LCD Display in order to show the 
voltage and current values: This values comes from an analogic digital 
converter, whose values are stored in a variable. The function "printf", 
used to show the values on display, doesn't refresh. I had to create a 
rotine that always call the printf function during the void loop, in 
order to refresh the values. But it refresh all the lines on display. 
This creates like a "blink effect", because all the caractheres are 
refreshed, instead only the ones that have been modified. There are some 
instruction that can refresh the variables automatically, without having 
to repeat the printf instruction all the time ?

Thanks !

von Tim S. (Company: tsx89) (freak_ts)


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In a HD44780 controller there are commands to set the "cursor", to can 
"overwrite" only some chars - instead of refresh the "entire screen".
There are "lcd-demos" with that controller, that can "draw" many frames 
per second for a smooth animation effect. May you writing to slow.
And i don't know what YOUR display controller is / behaves...

: Edited by User
von Lothar M. (Company: Titel) (lkmiller) (Moderator)


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JOSE P. wrote:
> There are some instruction that can refresh the variables automatically,
> without having to repeat the printf instruction all the time ?
The display itself is able to. You must read its datasheet and program 
your printf() function in a manner, that it doesn't use the "clear" 
command with each write.

Look how you can set the cursor to a certain position on the display and 
then simply overwrite the character at that position.

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