Go Down

Topic: Arduino Uno + LCD Keypad Shield (Read 390 times) previous topic - next topic

floresta

And connecting R/W to your Arduino still does not permit you to read the LCD with the current LiquidCrystal library so there is no reason not to connect it to GND and free up the I/O pin.

Don

OmegaOm

Thanks for all your help guys. 
Still I get no character displayed.  I tried all kinds of sample code related to my device, including sketch I found here, that uses a lcdkeypad h library that takes no arguments when initiating lcd object.

http://dimme.net/arduino-lcd-keypad-shield-clock-application/

It seems I have a faulty device, great for a beginner.

Unless problem has to do with back light being too bright as aisc said.
I how ever do not know how to change that, but looking closely at the screen it does not seems that is the problem.

floresta

Quote
It seems I have a faulty device, great for a beginner.
Not likely.


Quote
Unless problem has to do with back light being too bright as aisc said.
Even more unlikely.


Have you tried something simple like this:

Code: [Select]
#include <LiquidCrystal.h>

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);         // your pin numbers

void setup()
  {
  lcd.begin(16, 2);                          // your LCD parameters
  lcd.print("hello, world!");
  lcd.setCursor(0,1);
  lcd.print("it works!");
  }

void loop()
  {
  }


Don

OmegaOm

thanks Floresta, just tried it, but still doesnt work.  Just back light on thats it.
Even tried the blink sketch to see if uno is still working and it works.

cattledog

OmegaOm--
Have you tried adjusting the contrast potentiometer--the blue component in the upper left corner when looking at the shield with the buttons at the bottom. Don's code should be working with that shield, but if the contrast is set wrong you may not see the characters.

OmegaOm

cattledog, you are right and beat me to the post. 
I did figure this out tonight and came here to reply and seen your post.

I had to turn the screw a great deal to see anything.  Why the lcd was sold with the contrast pot set to invisible is beyond me.

Thanks all for your help.  Sorry for me being a noob and not figuring it out the tiny screw pot was the problem.

Im so glad it works.  Now I can get going.  thanks all for your time.


bperrybap

#21
Mar 25, 2015, 05:30 am Last Edit: Mar 25, 2015, 05:31 am by bperrybap
Just for information here are the number of permutations of pins when guessing:

if any of the 20 shield pins are used and 6 arduino pins are needed: 27,907,200
if any of the 20 shield pins are used and 7 arduino pins are needed: 39,0700,800

Now realistically, arduino pins 0,1, and 13 are typically not used so that cuts things down a bit:
any of 17 shield pins are used and 7 arduino pins are needed: 89,10,720
any of 17 shield pins are used and 7 arduino pins are needed: 98,017,920

And more than likely the r/w line is not used and the lcd shield only uses arduino pins from the top row on the arduino.
So that reduces to a best case of:
any of 11 pins (along the top row throwing out 0,1, and 13) and using 6 arduino pins: 332,640

Still quite a few permutations of how the LCD pins could be wired up to the Arduino pins so the odds of guessing the correct numbers for the constructor are pretty low.

--- bill

Paul__B

Remember to adjust the backlight intensity - it is often the cause why u cannot "see" the characters.
Please try and remember - it has nothing whatsoever to do with the backlight.

The control in question is the contrast voltage.

I had to turn the screw a great deal to see anything.
And apologies on behalf of the contributors to the forum, while this is the single most common problem when "My LCD doesn't work", it tends to seem so obvious to us that we just forget to make it the first answer to every such enquiry. :smiley-eek:

Along with not soldering (or at least using spring clips for) the connections to the LCD module which means it is simply not connected, and using eBay "Dupont" jumpers which are occasionally faulty.

The fact is, the historical reason why a 10k pot is used is that when the original company (Hitachi?) wrote the datasheet, they just happened to set it up using one lying around, so the crude test circuit they used was printed in the datasheet and the circuit was blindly copied by everyone since even to those other manufacturers who (quite legitimately, as far as we know) "cloned" the chip.  The correct position is within the first tenth of its range, at the ground end.  A 1k variable resistor from the "VO" pin on the LCD to ground would be usable over almost all of its range.

Why the LCD was sold with the contrast pot set to invisible is beyond me.
Hey!  You bought an assembled module.  By the way, from whom did you buy it?  Did you pay the extra surcharge for having it tested?

{Hope you do not think I am joking. :smiley-eek: }

floresta

#23
Today at 01:26 pm Last Edit: Today at 01:30 pm by floresta
Quote
The fact is, the historical reason why a 10k pot is used is that when the original company (Hitachi?) wrote the datasheet, they just happened to set it up using one lying around, so the crude test circuit they used was printed in the datasheet and the circuit was blindly copied by everyone since even to those other manufacturers who (quite legitimately, as far as we know) "cloned" the chip.  
Although this is a reasonable assumption it is hardly a fact.

Quote
And apologies on behalf of the contributors to the forum, while this is the single most common problem when "My LCD doesn't work", it tends to seem so obvious to us that we just forget to make it the first answer to every such enquiry.
It's interesting that the simple most common problem seems to evolve over time.  Several years ago the corresponding problem was the failure to connect R/W to GND.  This was alleviated when a caution was added to the tutorial but the caution has since been removed and perhaps this problem will once again overtake that of the contrast adjustment

Don


Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy