Tag: lcd

Testing composite video display with arduino

With TVout library it is possible to write and draw to framebuffer which is then sent to display using composite video. Result is below.


Coding is simple. Example code is below.

#include <TVout.h>
#include <fontALL.h>

TVout TV;

void setup() {
  TV.begin(PAL,144,96);
  TV.select_font(font8x8);
  TV.draw_rect(4,19,129,11,WHITE);
  TV.print(5,20,"This works fine.");
}

void loop() {
  // nothing here
}

Electrical connection follows TVout librarys default.

 

Controlling graphic dot matrix LCD display

This was very complicated project. Finally I learned how to successfully control display with Hitachi hd61830 controller chip and Arduino.

Display works with negative -13V and normal positive +5V voltages. So first I built necessary power supply. Below is it’s circuit drawing.

There is still some ripple voltage on negative line. Some more filtering is maybe needed (capacitors). Also zener goes very hot. Negative voltage regulator would be better choise for longer use. LM337 for example.

The next thing was to figure out how to control hd61830 controller chip with Arduino. Very helpful source code was found from LCDInfo forum. After that I was able to write my own code. It is below.

/* initialization sequence and cls function taken from lcd_hd61830_lib, cdragos69@yahoo.com
   http://www.skippari.net/lcd/sekalaista/lcd_hd61830_lib.zip
   found from http://forum.lcdinfo.com/viewtopic.php?t=451
*/

// pin assignment
const byte E_PIN = 4;
const byte RW_PIN = 3;
const byte RS_PIN = 2;
const byte DB7_PIN = 12;
const byte DB6_PIN = 11;
const byte DB5_PIN = 10;
const byte DB4_PIN = 9;
const byte DB3_PIN = 8;
const byte DB2_PIN = 7;
const byte DB1_PIN = 6;
const byte DB0_PIN = 5;

void setup() {
  // Permanently tied up E pin
  digitalWrite(E_PIN, HIGH);
  delay(2000);

  com(word(0x00, 0x38)); // Display ON, master mode, cursor on/blink, text mode, internal CG-ROM
  com(word(0x01, 0x75)); // 6x8 font
  com(word(0x02, 0x27)); // 40 horizontal characters
  com(word(0x03, 0x7F)); // 1/128 duty cycle (128 lines)
  com(word(0x04, 0x07)); // 8-lines cursor
  com(word(0x08, 0x00)); // Display start address low
  com(word(0x09, 0x00)); // Display start address high
  com(word(0x0A, 0x00)); // Cursor address low
  com(word(0x0B, 0x00)); // Cursor address high

  cls();

  com(word(B00001100, B01001000)); //letter H
  com(word(B00001100, B01100101)); //letter e
  com(word(B00001100, B01101100)); //letter l
  com(word(B00001100, B01101100)); //letter l
  com(word(B00001100, B01101111)); //letter o
  com(word(B00001100, B00100000)); //space
  com(word(B00001100, B01110111)); //letter w
  com(word(B00001100, B01101111)); //letter o
  com(word(B00001100, B01110010)); //letter r
  com(word(B00001100, B01101100)); //letter l
  com(word(B00001100, B01100100)); //letter d
}

void loop() {
  // nothing here
}

void cls() {
  // clear screen
  com(word(0x0A, 0x00)); // Cursor address low
  com(word(0x0B, 0x00)); // Cursor address high
  for(int i=0;i<320;i++) com(word(0x0C,0)); // reset all text memory
  com(word(0x0A, 0x00)); // Cursor address low
  com(word(0x0B, 0x00)); // Cursor address high
}

void com(word dat) {

  digitalWrite(LED_BUILTIN, HIGH); // data flow indication on

  digitalWrite(RW_PIN, LOW);
  digitalWrite(RS_PIN, HIGH);
  digitalWrite(DB7_PIN, bitRead(dat, 15));
  digitalWrite(DB6_PIN, bitRead(dat, 14));
  digitalWrite(DB5_PIN, bitRead(dat, 13));
  digitalWrite(DB4_PIN, bitRead(dat, 12));
  digitalWrite(DB3_PIN, bitRead(dat, 11));
  digitalWrite(DB2_PIN, bitRead(dat, 10));
  digitalWrite(DB1_PIN, bitRead(dat, 9));
  digitalWrite(DB0_PIN, bitRead(dat, 8));

  digitalWrite(RW_PIN, LOW);
  digitalWrite(RS_PIN, LOW);
  digitalWrite(DB7_PIN, bitRead(dat, 7));
  digitalWrite(DB6_PIN, bitRead(dat, 6));
  digitalWrite(DB5_PIN, bitRead(dat, 5));
  digitalWrite(DB4_PIN, bitRead(dat, 4));
  digitalWrite(DB3_PIN, bitRead(dat, 3));
  digitalWrite(DB2_PIN, bitRead(dat, 2));
  digitalWrite(DB1_PIN, bitRead(dat, 1));
  digitalWrite(DB0_PIN, bitRead(dat, 0));
  
  digitalWrite(LED_BUILTIN, LOW); // data flow indication off

  //wait for busy flag to go away
  digitalWrite(E_PIN, HIGH);
  digitalWrite(RW_PIN, HIGH);
  digitalWrite(RS_PIN, HIGH);
  do {
    delay(10);
  } while (digitalRead(DB7_PIN) == HIGH);
}

Display is on text-mode with internal character ROM. The next challenge is to draw something on screen. There is some more images in the meantime. Contrast trimmer is seen on centre of image and zener is it’s left side.