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LCD HD47780 interfacing

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Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

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weijie

Sun Jul 13 2008, 08:23PM

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@sashijoseph

the line of " for( i=0 ; i<750 ; i++) " is use to ?
eg : lets say i call void delay(160) , then the result delay will be ? crystal that i using is 22.184MHz
my delay aim are use to generate delay in term of microsecond as the minimum time to execute a command for LCD is 40us.
Is it better to check busy flag compare to using delay ? because some forum comment that checking busy flag is not advisable to use .

[ Edited Sun Jul 13 2008, 08:27PM ]

Arun Kumar V

Mon Jul 14 2008, 12:46AM

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Joined: Sun Jan 28 2007, 11:50PM

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Checking Busy flag is always better, bcoz it gives the controller inside the LCD sufficient time to complete what its doing (internally).

on the other hand, the delay which we do in the code may or may not give the LCD controller enough time for its internal operation.

also checking busy flag method enables you to use same code on different micros (Single cycle micro or 12 cycle normal micro) without recalculating delay timings and machine cycle time.

Arun

weijie

Mon Jul 14 2008, 07:24AM

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thks alot ~
my circuit are working already ... thks for the help everyone

weijie

Sat Jul 26 2008, 08:34AM

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void LCD_busy()
{
LCD_D7 = 1; //Make D7th bit of LCD as i/p
LCD_en = 1; //Make port pin as o/p
LCD_rs = 0; //Selected command register
LCD_rw = 1; //We are reading
while(LCD_D7){ //read busy flag again and again till it becomes 0
LCD_en = 0; //Enable H->L
LCD_en = 1;
}
}

according to the code above, we need to set the LCD_en as 1 as a output port .
But why when checking the busy flag(LCD_D7) , it is toggled from 0 to 1 but not 1 to 0 ? i thought we should use toggle from high to low every time ?

sashijoseph

Sat Jul 26 2008, 07:26PM

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Hi....
In the above code LCD_en = 1; //Make port pin as o/p is not needed.
If you look at the LCD timing diagram,a read requires EN->L to H strobe while a write requires H to L.
Since you are reading the busy flag,a L to H is reqd for the enable pin.

[ Edited Sat Jul 26 2008, 07:28PM ]

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