Arduino and LCD - can't see text ...

[gatorbait3]

I just got one of the LCD 16x2 kits for my Arduino .. and am not seeing any data on it!

The contrast pot works fine and shows the "white blocks" on the LCD. However, running tutorial code doesn't produce any text on the LCD.

I've reviewed and rewired the LCD lines to the Arduino several times. I've also checked the header solder points to make sure non are shorting to the neighboring pin, and tried moving the 4 - data lines to other pins on the Arduino (with corresponding changes to the code for the new pins).

I've also added an "LED flash" statement to the code which flashes the on-board LED as the loop iterates, along with serial.println statements for debug .. and this works fine.

I've also measured the RS and EN lines to make sure they are getting voltages, which they are. I've also reviewed the data sheet and even tried hooking up all 8 data lines. Also looked at the LiquidCrystal.h file and tried some of the other functions available too (i.e. home, clear, cursor on, etc.).

But no data out!! Any suggestions on what else to look at? Could the LCD panel be bad?

[adafruit]

its somewhat unlikely that you're seeing squares but not text. please wire up the LCD according to the tutorial and tutorial text on ladyada.net nad then post a photo showing your wiring so we can verify it

[gatorbait3]

First, I want to thank you for taking a look! I really appreciate it!

Photos of wiring (all are thumbnails to MUCH larger images!): (EDIT-links to large images removed)



While the code is running, I've dialed the contrast pot end to end and don't see any text (just the "white blocks" with full contrast). Output to the console shows the expected results, and the on-board LED flashes with each loop.

Sketch I'm using (the base tutorial LCD one, plus debug stuff - flashing LED and serial prints):

Code: Select all

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  // send debug statements to console
  Serial.begin(9600);
  // set up LED to blink
  pinMode(13, OUTPUT);
  // 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() {
  Serial.println("Loop begin - turn on LED");
  digitalWrite(13, HIGH);   // set the LED to be on while message is going to LCD
  Serial.print("Set LCD line and print result: ");
  Serial.println(millis()/1000);

  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(millis()/1000);
 
  Serial.println("  Loop end - turn off LED");
  digitalWrite(13, LOW);    // set the LED off after message sent and loop is ending
  delay(500);
  Serial.println("==================================");
}

[adafruit]

check the soldering of the header to the LCD, that could be a problem

[gatorbait3]

That was it!!!

I resoldered all the header pins and now it works! Great eye! I was trying to be careful not to have "bleed over" with the solder to the surrounding pins and must have gotten a cold solder joint or one with not enough solder to make a good, consistent connection.

Thank you again for that suggestion .. while I checked continuity with a meter to surrounding pins, I didn't check bottom of pin to pad.

Time to go play now!! And you can mark this one "SOLVED!"