Cannot write "hello, world!" to LCD thru backpack

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jethro
 
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Joined: Sat Apr 05, 2014 5:52 pm

Cannot write "hello, world!" to LCD thru backpack

Post by jethro »

I am having difficulty with running a sketch on my Arduino UNO R3.
I have already compiled & uploaded the "blink" sketch. It runs fine.
I modified it, verified that I could compile changes to the timing of
the blinks using calls to the delay() function, and reloading the
code.

After running blink, I figured the next logical step would be writing
to an LCD. This is my first attempt to do so.

I find that I cannot write to Lady Ada's "16x2 LCD" (Adafruit PID: 398)
connected to her "LCD I2C/SPI backpack" (Adafruit i2c/SPI character LCD
backpack PID: 292) using 4 wires (triple checked the 4 wires).

Other than soldering the header pins to the LCD, and then to the LCD
backpack, I did no other modification to the PCB.
Yes, I made sure that pin 1 of the LCD backpack lined up with pin 1 of
the LCD.

The LCD backpack/LCD combo. is the only device connected to the
Arduino.

I ran robertogi's I2C scanner sketch. It showed:
"Found address 32 (0x20)
Done.
Found 1 device(s)."
Okay, so I guess this means the LCD backpack has an I2C address.
(This is my first time using an I2C device too.)

To test the LCD, I loaded Lady Ada's Hello_World_i2c sketch from the
Arduino IDE. Yes, I "installed" the "Adafruit_LiquidCrystal.h"
library first.

I figured this program would display "hello world!" without my
having to changeanything in the code or on the PCB. But it didn't.

No compiler errors occurred when I ran Lady Ada's Hello_World_i2c
sketch.

I verified that all 16 pins of the LCD are connected to the backpack,
and that no two pins are shorted, three times. I put an index card
between the backpack PCB and the LCD to ensure there can be no shorts.

Upon running Lady Ada's HelloWorld_i2C sketch all the pixels on
the 16x2 LCD (Adafruit #398) turn dark, and none on the bottom row.
I turned the set screw on the back of the LCD until the text becomes
visible. However every pixel in every character cell is turned on,
not the message.

The backlight turns orange & flashes on and off every half second or so.
Nothing else changes.


Is the LCD defective? Is it possessed by the devil ? :)
Any suggestions ?


Jethro

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adafruit_support_bill
 
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Joined: Sat Feb 07, 2009 10:11 am

Re: Cannot write "hello, world!" to LCD thru backpack

Post by adafruit_support_bill »

Please post some photos showing your soldering and connections to the backpack.

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