Data vision display not working

[ON7EN]

hi i have a large datavision display dvf-20210-1

2x20 caracters it should be compatible with hd44780
i connected it but i have only black rectangles

has somebody experians with this display ?

DATA INTERNATIONAL CO., LTD

thanks for answer

jean-marie

[gilshultz]

Be sure you wired it correctly, if it is adjust the contrast pot! Let us know if that solved it. The link was a big help.

[ON7EN]

hi gilshultz

thanks for answer

first i followed the schematic on the link.

but no contrast.

then i found an info that these lcd's need a negative bias on pin 3 because they have a large temperature range.

i used a 9v battery. now i have contrast and 2x20 black boxes on the display

when you use the backlight you need 500mA at 4V

i used the standard arduino example to display " hello world"

but no luck no text

regards jean-marie

[ON7EN]

hi i found a solution

display works only in 8 bit mode and you need to feed a negative voltage to pin3

regards jean-marie

my sketch:
#include <LiquidCrystal.h>

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int RS = 12, EN = 11, D0 = 10, D1 = 9, D2 = 8, D3 = 7 , D4 = 6, D5 = 5, D6 = 4, D7 = 3;

LiquidCrystal lcd(RS, EN, D0, D1, D2, D3, D4, D5, D6, D7); // 8-bit mode
void setup() {
// set up the LCD's number of columns and rows:
lcd.begin(20, 2);
// Print a message to the LCD.
lcd.print("ON7EN");
}

void loop() {
// 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);
}