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HD44780 LCD help : How to understand it is initialized?

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Member level 4
Mar 19, 2009
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Zurich, Switzerland
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Dear all,

I want to use a HD44780 for a hobby circuit. So I have connected with my PIC MCU in a 4-wire interface and tried to communicate with it.

However I cannot display anything on the LCD. I will try to troubleshoot my design but I need to know something pretty important! I cannot understand whether the LCD has been initialized or not..(I have put some code in my program for initializing)

After connecting the power supply the LCD is not dark.. on the contrary it seems that the background light is on.. is this an indication that it is initialized? I have not used any LCD before.

1. Make sure that you pin 3 is either connected to GND or to the center of a potentiometer (its better using a potetiometer).
2. If you use the potetiometer, you can swing the contrast from full dark to blank screen, this is good sign.
3. After you send the init code, your display contrast will shift and all should be about the same color.
4. Send some data and the text will appear.

* Make sure that the E signal is not grounded. The E is a strobe to shift in data/command to the LCD.
* Also make sure that your RS line is set correctly before each command or data being sent.

The backlight is independent of the display, the backlight only tells you that you have a supply voltage.

This should help.

Good luck.


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