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Running an HD44780 Display off the ATmega on a Gertboard




There was a thread on the Raspberry Pi forums about running a 16×2 HD44780 based display off the ATmega chip on the Gertboard.  I normally use a shift register to run my display, so I wasn’t much help to them.  I decided to try and get it setup without the shift register to help out the folks having trouble.
Running an HD44780 Display off the ATmega on a Gertboardhd44780
So, this instructable will detail how to go about getting an HD44780 display running off the ATmega chip on the Raspberry Pi Gertboard.

Step 1: Ground an 5V

The first step is to connect the display to ground and 5V on the Gertboard.  Because you have to connect a pot to the contrast, I hooked up the Ground and 5V to my breadboard, and plugged the display into that.

Step 2: Contrast

Pin 3 on the display controls Contrast. It’s connected from Pin 3 to a 1k pot to ground.

The output from Pin 3 gets connected to one side of the pot, and ground to the middle leg of the pot.

Step 3: Register Select

Pin 4 is Register Select.  This is our first pin connected to the ATmega chip on the Gertboard.  I chose pin 8, which is marked as PB0, just because I could.

I added some white lines in the picture to help clear up where each pin was, as it was hard to tell.

 

For more detail: Running an HD44780 Display off the ATmega on a Gertboard

 

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