HI,
I discovered the arduino.
I followed the lab
display() and noDisplay() methods
I check the wiring several times, changed the UNO by Nano; But still display problem with white squares; The potentiometer is a B20K
Here is the assembly
montage
an idea please
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
We have to see your code and can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Thanks… Tom… 
thank you for your answer.
see the link on my first text!
Hi,
Your montage link doesn't work.
And please post your code.
Please post a picture of your project please.
Links to off forum pictures and code do not work on ipad or phone platfroms.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
Thanks.. Tom.. 
PS. You help us we can help you.
The only problems I've had using a 16x2 LCD with the arduino library have been through my own stupid wiring errors....
Allan
/*
LiquidCrystal Library - display() and noDisplay()
Demonstrates the use a 16x2 LCD display. The LiquidCrystal
library works with all LCD displays that are compatible with the
Hitachi HD44780 driver. There are many of them out there, and you
can usually tell them by the 16-pin interface.
This sketch prints "Hello World!" to the LCD and uses the
display() and noDisplay() functions to turn on and off
the display.
The circuit:
* LCD RS pin to digital pin 12
* LCD Enable pin to digital pin 11
* LCD D4 pin to digital pin 5
* LCD D5 pin to digital pin 4
* LCD D6 pin to digital pin 3
* LCD D7 pin to digital pin 2
* LCD R/W pin to ground
* 10K resistor:
* ends to +5V and ground
* wiper to LCD VO pin (pin 3)
Library originally added 18 Apr 2008
by David A. Mellis
library modified 5 Jul 2009
by Limor Fried (http://www.ladyada.net)
example added 9 Jul 2009
by Tom Igoe
modified 22 Nov 2010
by Tom Igoe
This example code is in the public domain.
http://www.arduino.cc/en/Tutorial/LiquidCrystalDisplay
*/
// include the library code:
#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup() {
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello, world!");
}
void loop() {
// Turn off the display:
lcd.noDisplay();
delay(500);
// Turn on the display:
lcd.display();
delay(500);
}
do you have the pot for the display cranked up too high ?
Hi,
Sorry your picture did not show.
It would be best to attach the image file to you next post.
Thanks.. Tom..
It looks as if the contrast is set wrongly. 820k is a very high value pot - I always used 10k.
Allan
Hi,
OPs Picture.
Thanks… Tom…
Hi,
Try this.
You do not need to gnd all the unused Data pins on the LCD.
The resistor for the LCD back light, 220R, in your picture looks like it will not work where it is on the protoboard
What are you using for Vin?
Thanks… Tom…
i use DC Power Suppy MCH-K305D 7.5V
I unplug all unused data PINs from GND
The resistor 200 Ohm is on PIN A (LED+) LCD to Power 5V
I make this Tuto and work fine. I see it use RX and TX.
All tuto use PIN 11 and 12 not work for me...
I try to understand
Hi,
Have you got a DMM?
Measure the voltage off the wiper of the pot, make sure it goes smoothly from 0 to 5V, with 2.5V at half way.
Tom..
The measurement gives 0v to 4.88v - to set race on a close of 2.5v - carried multimeter on PWM potentiometer and support + multimeter on + potentiometer
