Can't get Grove LCD Twig to work

End-Of-Life Products & Services Tech support before 2012
#1

My LCD module for the LCD twig arrived, and I tried to run Project 6 to demonstrate it. The LCD lights up brightly, but doesn’t show any characters. I tried adjusting the resistor on the twig, and that made parts of the LCD a bit dimmer but didn’t make characters appear. I do have the library software installed, and the sketch compiles correctly. I tried adding the dual-LED twig and some code to blink the LEDs when the LCD code does each step, and that blinked when I expected it to, but no characters appear on the LCD. And I checked that all my cable connections were tight and plugged in to the correct jacks, and I even swapped the cables in case the project directions were backwards, but it didn’t help.

How can I debug this? There’s no circuit diagram, and I’m only guessing that the resistor on the twig is adjustable, and it has no information about whether it only goes one turn or many. What do the other jacks on the LCD twig do - should the cables from the Stem actually use them instead of the ones it specifies?

Thanks; Bill – billstewart@pobox.com

#2

Bill,you can try to connect the LCD0802 to arduino/seeedstudio according to this website:http://www.seeedstudio.com/depot/lcd-82-characters-blue-back-light-p-120.html?cPath=93_98&zenid=f56f3ac4f7dc82c593ca23d9e72752d3

If it still don’t work,I am sure that your LCD0802 is broken.

#3

I had the same problem as Bill initially. I had to change a couple of things in order for the LCD Demonstration program in the Grove documentation to work (garden.seeedstudio.com/index.php … onstration)

  1. The contrast needed to be changed from the default setting. There is a small potentiometer for this, on the LCD’s “stem”, marked R1. If you don’t see some “block” characters on the first line when you initially plug in the Arduino, then the contrast probably needs to be adjusted.

  2. I’m not sure if I downloaded the wrong LiquidCrystal library from Seeed’s site, but the one I have (from seeedstudio.com/depot/images … rystal.rar) isn’t compatible with the sample code in the Grove documentation. There isn’t a constructor that takes only 6 parameters, and there isn’t a begin function.

So, I connected a 4th cable to the upper right connector on the LCD stem, and plugged it into the D11/D12 connector on the Grove shield. I changed the constructor and begin function in the sample code to:

//LiquidCrystal lcd(1,2,3,4,5,6);
LiquidCrystal lcd(5,11,6,7,8,9,10); // pin 11 is RW

void setup()
{
//lcd.begin(8,2);
}

By the way, the connectors on the LCD stem are labelled on the back of the stem board. The upper right one is for RW, and the two on the top side of the stem are only used for 8-pin LCD connections (which require 4 more parameters in the LiquidCrystal constructor).

Dan.

#4

The LiquidCrystal lib has its problem, so change the pins may cause problem at my practice.