LCD show only black boxes Is it pull up problem?

lobos_dario · May 14, 2025, 3:10pm

NOW I ADDED A MAKEFILE TO FLASH DIRECT WITH AVRDUDE THE AVRGCC C90 PROGRAM Added -D in flash. IS BELLOW. I REVISED AGAIN Missing * for pointer value. CHANGED DELAY MICRO BY UTIL/DELAY.H _delay_us(). I ADDED FRITZING CIRCUIT AND THREE OPTIONS OF CONTROLLER IN THE CODE. I am trying to use and LCD 16 x 2 and shows only black boxes with a library example and with a direct port manipulation program that I want to implement. Controller HD44780 don't mention in the datasheet a command to determine internal pullups BIAS resistors FOR WAVE VOLTAGE IN FRAME 1/16. But ST7070 yes. I have no experience in it at all. I want to know if this can be the problem and which pullups are convenient because I use only 4 data and other are not connected and can send bad values without a resistors.
Command in St7070 rs:0 rw:0 D: 000001xx in the datasheet xx 2.2k, 6.8k and 9 k

CAN BE THIS THE PROBLEM ?

THIS IS THE CIRCUIT DRAWING:

https://drive.google.com/file/d/105jxT2YLWTsHt7iJGs_oO9WbeYaBA4UH/view?usp=drivesdk

Photos are these:

This is the datasheet print screen with the set extended functions mentioned in ST 7070

https://drive.google.com/file/d/1EQPdluNiqCxRsXbA6WAnaVhnrrmUHsPe/view?usp=drivesdk

https://drive.google.com/file/d/1EPQ_VJhpxoP5XvzmEixg1-sP0pPcM3zq/view?usp=drivesdk

https://drive.google.com/file/d/1EQaa9kTp2FsJuegxwTxgaiT7awEoMsvJ/view?usp=drivesdk

https://drive.google.com/file/d/1EUGiz4xFTWN6ae5Oteb8voL4pkIm3WbV/view?usp=drivesdk

The unfinished code is this:

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define F_CPU 16000000UL

// I gonna use a delay making a watchdog and interruption to permit other operations
// during display startup
// THIS IS FOR WATCH DOG PRESCALLER TIMER WHILE A DELAY IS RUNNING OTHER OPERATIONS
// CAN BE DONE UNTIL LCD FINISH ITS DUTIES
// WATCH DOG CLOCK IS 128 KHZ 7.8 MICROSECONDS
// THE REGISTER OF WATCHDOG IS WDTCSR
// FIST 4 BITS DETERMINE THE TIMEOUT LIMIT BY OVERFLOW
// 0000 (WPD3, WPD2, WPD1, WPD0) LIMIT IS 16 ms
// 0001 is 32ms
// 0010 is 64ms
// 0011 is 125 ms
// 0100 is 250 ms
// 0101 is 0.5 s
// 0110 is 1 s
// 0111 is 2 s
// 1000 is 4 s
// 1001 is 8 s
// rest are reserved bits
// WDTCSR |= 1 <<< WDIE6 ENABLE WATCHDOG INTERRUPT (BIT 6)



// THIS IS LCD HANDLING USING DIRECT MANIPULATION 
// AND AN LCD LCM 1602 A WITH ST7063 CONTROLLER 
// IMPORTANT NOTE LCM1602A AND ST7063 AND HD 44780 ARE DIFFERENT I WILL LEAVE INITALIZATION FUNCTION FOR THE THREE TYPES
// ENABLE TIME FOR INITIALIZATION IS NOT DEFINED IN DATASHEETS THAT IS SOMETHING AMBIGUOUS ASSEMBLY EXAMPLE DONT USE ANY
// DELAY BUT IS MANDATORY A DELAY IN READ AND WRITE THAT PULSE REQUIREMENTS VARY FORM 400 TO 1200 nS 
// DARIO LOBOS 13/MAY/2025


  
// THESE ARE BITWISE FUNCTION NEEDED TO HANDLE DATA 

void setBit( uint8_t b, uint8_t pos){

uint8_t *n = &b;
uint8_t bit = 1 << pos; 
*n = *n | bit;

}

uint8_t bitON( uint8_t n,uint8_t pos){
return ( (n & (1<<pos))!=0);
}

uint8_t counterBitON(uint8_t data){
  int count=0;
  while(data){
      data &= (data-1); 
      count++;
    }
  return count;  
  }
  

void delayNanos(int nano){

_delay_us(nano*1000);

}

/*
 * The circuit:
 * LCD RS pin to digital pin 7
 * LCD Enable pin to digital pin 13
 * LCD D4 pin to digital pin 2
 * LCD D5 pin to digital pin 3
 * LCD D6 pin to digital pin 4
 * LCD D7 pin to digital pin 5
 * LCD R/W pin 12
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
* ends to +5V and ground
 * VO is contrast to a potenciomenter 100 ohm + 220 ohm to ground  2 parallel 1 kohm to Vcc 220 Vo ? 1 volt (can be higher resistors divider )
*/

// PINS 2,3,4,5,7 ARE PORTD AND DDRD 
// PINS 12, 13 ARE PORT B DDRB

// ACCORDING DATASHEET ST7066U and LCM1602A  
// ENABLE CYCLE MINIMUN 1200 nS (600 on / 600off) FOR ST7066U
// ENABLE CYCLE MINIMUN 1000 nS FOR HD44780
// ENABLE CYCLE IS 400 nS FOR LCM1602A

// MODE OF OPERATION FOUR BITS SO A BYTE 8 BITS IS SENT IN TWO SETS FIRST 4 HIGH THEN 4 LOW
// THIS USE D4,D5,D6,D7 (0,1,2,3 ARE DISCONNECTED)
// DATA IS ACCORDING ASCII CODE
// ENABLE MUST PUT IT ON TO READ OR WRITE DATA
// READ IS TO READ FLAG IN D7 WHICH IS BUSY FLAG WHILE IS HIGH MUST NOT BE SENT DATA TO THE LCD ONLY IS AVAILABLE WHEN IS 0
// TO SET DDRAM  ADDRESS D7 MUST BE HIGH THEN THE 7 BITS FOR THE ADDRESS 
// IN 16 X 2 ADDRESS OF FIRST LINE ADDRESS  START IN 00 AND FINISH IN 0F (OR 15 IN DECIMAL)
// IN 16 X 2 ADDRESS OF SECOND LINE ADDRESS  START IN 40 (OR 64 IN DECIMAL) AND FINISH IN 4F (OR 79 IN DECIMAL OR  b1001111)
// SO TO WRITE 40(SECOND LINE START IN FOUR BITS 1100 0000 THE SECOND SET OF FOUR BITS
// FUNCTIONS OR COMMANDS ARE IN REGISTERS ARE:
// CLEAR DISPLAT 0000 0001
// RETURN HOME 0000 001x   x can be 0 or 1
// ENTRY MODE SET 0000 0100 DECREMENT NEXT REGISTER MEMORY POSITION 
//                0000 0101 DECREMENT NEXT REGISTER POSITION AND DISPLAY SHIFT (THIS IS SHIFT TO THE LEFT)
//                0000 0110 INCREMENT NEXT REGOSTER MEMORY POSITION
//                0000 0111 INCREMENT NEXT REGISTER POSITION AND DISPLAY SHIFT (SHIFT TO THE RIGHT)
// DISPLAY ON/OFF 0000 1000 SET ENTIRE DISPLAY OFF, CURSOR OFF 
//                0000 110B SET ENTIRE DISPLAY ON, CURSOR OFF
//                0000 111B SET ENTIRE DISPLAY ON, CURSOR ON
//                0000 111B SET ENTIRE DISPLAY ON
//                B= 1 Blink cursor on , = 0 off
// CURSOR OR 
// DISPLAY SHIFT  0001 00xx MOVE CURSOR TO THE LEFT WITHOUT CHANGE MEMORY DATA
//                0001 10xx MOVE DISPLAY TO THE LEFT WITOUT CHANGE MEMORY DATA
//                0001 01xx MOVE CURSOR TO THE RIGHT WITHOUT CHANGE MEMORY DATA
//                0001 11xx MOVE DISPLAY TO THE RIGHT WITHOUT CHANGE MEMORY DATA
// FUNCTION SET   0010 00xx MODE 4 BITS DATA BUS, ONE LINE, FONT 5 X 8
//                0011 00xx MODE 8 BITS DATA BUS, ONE LINE, FONT 5 X 8
//                0010 O1xx MODE 4 BITS DATA BUS, ONE LINE, FONT 5 X 11
//                0011 01xx MODE 8 BITS DATA BUS, ONE LINE, FONT 5 X 11
//                0010 10xx MODE 4 BITS DATA BUS, TWO LINES, FONT 5 X 8
//                0011 10xx MODE 8 BITS DATA BUS, TWO LINES, FONT 5 X 8   
//                0010 11xx MODE 4 BITS DATA BUS, TWO LINES, FONT 5 X 11
//                0011 11xx MODE 8 BITS DATA BUS, TWO LINES, FONT 5 X 11
// SET CGRAM 
// ADDRESS        01AA AAAA A= A IS THE ADDRESS OF CUSTOM CHARACTER
// SET DDRAM 
// ADDRESS        1AAA AAAA A= A IS THE ADDRESS OF THE POSITION OR SHIFTED POSITION ( SEE DATASHEET FOR MORE DETAILS)
// BUSY FLAG R/W = 1 (READ) AND D7=1
// WRITE DATA E=1, RS=1 R/W=0
// READ DATA E=1 RS=1 R/W=1
 
// I WILL DO JUST EASY SIMPLE FUNCTIONS FAST STRING SHOULD BE >16

// OPERATION MODE IS INIIALIZING BY INSTRUCTION

// H= HD 44780
// L= LCM1602A 
// S= ST7063

volatile char controller;

void operationMode(char control){

WDTCSR = (WDTCSR | 1 << WDIE) & ~(1<< WDE) ; // ENABLE WATCHDOG INTERRUPT MODE WITHOUT SYSTEM RESET
	
WDTCSR = 1 << WDIE | 1<< WDP2 | 1 << WDP0; // SET WATCHDOG 500 ms timeout
	
// delay(500); // set up can't be modified even reseting the arduino. must be power off the LCD

controller= control;
}


ISR(WDT_vect){ // THIS IS THE ACTION THAT WILL BE DONE AFTER 500 ms watchdog
  
 DDRD = (DDRD | 0b10111100); // RS = OUTPUT, PIN 7  DATABITS OUTPUT, PINS 2,3,4,5
 DDRB = (DDRB | 0b00110000); // ENABLE = OUTPUT, PIN 13 AND R/W=OUTPUT, PIN 12 

if (controller=='H'){

// FIRST FUNCTION SET
 PORTB = (PORTB | 0b00100000) & 0b11101111 ; // ENABLE=1 R/W=0
 PORTD = (PORTD | 0b00001100) & 0b01111111 ; // RS=0 D5=1 D4=1
// delayNanos(500);

 _delay_us(1);
 PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(500);
 delayNanos(4200);

 PORTB = (PORTB | 0b00100000) & 0b11101111 ; // ENABLE=1 R/W=0 SECOND FUNCTION SET
 PORTD = (PORTD | 0b00001100) & 0b01111111 ; // RS=0 D5=1 D4=1 I REPEAT FOR THE TIME OF E ON/OFF
// delayNanos(500);
_delay_us(1);
  PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(500);
  delayNanos(4200); 

// HD 44780 NEEDS THREE 
 PORTB = (PORTB | 0b00100000) & 0b11101111 ; // ENABLE=1 R/W=0  THIRD FUNCTION SET
// delayNanos(500);
 PORTD = (PORTD | 0b00001100) & 0b01111111 ; // RS=0 D5=1 D4=1 I REPEAT FOR THE TIME OF E ON/OFF
//  delayNanos(500);
_delay_us(1);
 PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
//  delayNanos(500);
 _delay_us(110);
 
// THIS IS NOW THE SET FOR DEFINE OPERATION MODE 4 BITS 
 PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 Second set function same as first.
 PORTD = (PORTD | 0b00001000) & 0b01001011 ; // RS=0 D5=1 D4=0
//  delayNanos(500); 
_delay_us(1);
 PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(500);
 _delay_us(39);
 
// THIS IS NOW THE SET FOR DEFINE OPERATION MODE AND 2 LINES HIGH BITS 
 PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 Second set funcion same as first.
 PORTD = (PORTD | 0b00001000) & 0b01001011 ; // RS=0 D5=1 D4=0
//  delayNanos(500); 
 _delay_us(1);
 PORTB = PORTB & 11011111 ; // ENABLE=0 R/W=0
// delayNanos(500);
 _delay_us(1);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b00100000) & 0b11100011 ; // NEXT LOW BITS TO DEFINE OPERATION D7= 1 TWO LINES 
// delayNanos(500);
_delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(500);
 _delay_us(39);
}

if (controller=='L'){
  // FIRST FUNCTION SET
// LCM 1602A START LIKE THIS 
 PORTB = (PORTB | 0b00100000) & 0b11101111 ; // ENABLE=1 R/W=0
 PORTD = (PORTD | 0b00001000) & 0b01111111 ; // RS=0 D5=1 D4=0
// delayNanos(200);
_delay_us(1);
// PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(200);
 _delay_us(39);
 
// THIS IS NOW THE SET FOR DEFINE OPERATION MODE AND 2 LINES HIGH BITS 
 PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
 PORTD = (PORTD | 0b00001000) & 0b01001011 ; // RS=0 D5=1 D4=0
//  delayNanos(200); 
_delay_us(1);
 PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(200);
 _delay_us(39);
 
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b00100000) & 0b11100011 ; // NEXT LOW BITS TO DEFINE OPERATION D7= 1 TWO LINES 
// delayNanos(200);
 _delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(200);
_delay_us(39);

}

if (controller=='S'){

// FIRST FUNCTION SET
 PORTB = (PORTB | 0b00100000) & 0b11101111 ; // ENABLE=1 R/W=0
 PORTD = (PORTD | 0b00001100) & 0b01111111 ; // RS=0 D5=1 D4=1
// delayNanos(600);
 _delay_us(1);
 PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
_delay_us(39);

// THIS IS NOW THE SET FOR DEFINE OPERATION MODE AND 2 LINES HIGH BITS ST7066U DUPLICATE THIS
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 Second set function same as first.
 PORTD = (PORTD | 0b00001000) & 0b01001011 ; // RS=0 D5=1 D4=0
//  delayNanos(600);
 _delay_us(1);
  PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
 _delay_us(1);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b00100000) & 0b11100011 ; // NEXT LOW BITS TO DEFINE OPERATION D7= 1 TWO LINES 
// delayNanos(600);
 _delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
_delay_us(39);

// THIS IS NOW THE SET FOR DEFINE OPERATION MODE AND 2 LINES HIGH BITS ST7066U DUPLICATE THIS
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 Second set funcion same as first.
 PORTD = (PORTD | 0b00001000) & 0b01001011 ; // RS=0 D5=1 D4=0
// delayNanos(600);
_delay_us(1); 
 PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
 _delay_us(1);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b00100000) & 0b11100011 ; // NEXT LOW BITS TO DEFINE OPERATION D7= 1 TWO LINES 
// delayNanos(600);
 _delay_us(1);

PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
_delay_us(39);


}

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD & 0b01000011); // DISPLAY ON CURSOR OFF HIGH ALL BITS 0 (PIN 6 IS RESERVED FOR PWM, PIN 0 AND 1 ARE Serial)
// delayNanos(600);
 _delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
_delay_us(1);
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b00110000); // DISPLAY ON CURSOR OFF LOW BITS D3=1 D3=2 DISPLAY ON D1=1 CURSOR OFF D0= FONT 1 
// delayNanos(600);
 _delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
_delay_us(39);


PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = PORTD& 0b11000011 ; // DISPLAY CLEAR HIGH  ALL CERO
// delayNanos(600);
_delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
_delay_us(1);
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b00000100); //  DISPLAY CLEAR LOW  BITS D6=1 D5=1
// delayNanos(600);
 _delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
delayNanos(1550);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = PORTD & 0b01000011 ; // HIGH BITS OF ENTRY MODE ALL CERO
// delayNanos(600);
 _delay_us(1);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
// delayNanos(600);
 _delay_us(1);
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = PORTD | 0b01011011 ; // LOW BITS OF ENTRY MODE CURSOR MOVES TO RIGHT AND ADDRESS INCREMENT BY 1 EACH STEP
// delayNanos(600);
 _delay_us(1);
PORTB = (PORTB & 0b11011111) | 0b00010000; // ENABLE=0 R/W=1
// delayNanos(600);
_delay_us(39);

// THIS IS TO TEST INIT DOING AN H CHARACTER

if (controller=='S'){

PORTD = (PORTD | 0b10000000 | 0b00010000) & 0b11010011; // RS= 1 WRITE DATA HIGH BITS;
 delayNanos(600);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(600);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b10000000 | 0b00100000) & 0b11100011; ; // RS= 1 D7=1 WRITE DATA LOW BITS;
delayNanos(600);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(600);

}

if (controller=='H'){

PORTD = (PORTD | 0b10000000 | 0b00010000) & 0b11010011; // RS= 1 WRITE DATA HIGH BITS;
delayNanos(500);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b10000000 | 0b00100000) & 0b11100011; ; // RS= 1 D7=1 WRITE DATA LOW BITS;
delayNanos(500);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);

}

if (controller=='L'){

PORTD = (PORTD | 0b10000000 | 0b00010000) & 0b11010011; // RS= 1 WRITE DATA HIGH BITS;
delayNanos(200);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(200);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = (PORTD | 0b10000000 | 0b00100000) & 0b11100011; ; // RS= 1 D7=1 WRITE DATA LOW BITS;
delayNanos(200);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(200);

}

     
PORTD = PORTD & 0b01000011 ; // PUT DATA BUS IN CERO
_delay_us(50);
PORTD = (PORTD | 0b00111100);   // PULL UP RESISTOR INPUT MODE 
DDRD = (DDRD & 0b11000011); // RS = OUTPUT, PIN 7  DATABITS INPUT, PINS 2,3,4,5

cli();
sei();
}

void displayFirtLine ( char  text[]){

    char * msgchar = & text[0];

    uint8_t charBits [sizeof(text)-1][1];

    uint8_t center = (16 - (sizeof(text)-1))/2-1; // IN FIRST LINE DDRAM ADDRESS START IN CERO SO THIS WILL BE FIRS MEMORY POSITION

    // THIS IS TO CHECK BUSY FLAG BEFORE CONTINUE

PORTB = (PORTB | 0b00110000); // ENABLE=1 R/W=1
PORTD = (PORTD & 0b01000011); 
 
while (bitON(PORTD,5)){
// WAIT UNTIL BUSY FLAG IS 0
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
delayNanos(500);
 
} 

PORTB = (PORTB & 0b11101111); // ENABLE=1 R/W=0
DDRD = (DDRD | 0b00111100); // RS = OUTPUT, PIN 7  DATABITS OUTPUT, PINS 2,3,4,5

PORTD = ((PORTD | 0b00100000) & 0b01100011)| (center>>4)<<2 ; // RS= 0 D7=1 WRITE ADDRESSS OF START MEMORY HIGH BITS;
delayNanos(500);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);


PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0       
PORTD = (PORTD & 0b01000011)| ((center<<4)>>4)<<2 ; // RS= 0 WRITE ADDRESSS OF START MEMORY LOW BITS;
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);

uint8_t i=0;
uint8_t z=sizeof(text)-1;
for (i=0; i<z; i++){
msgchar+=i;
charBits [i][0] = (*msgchar) >> 4;
charBits [i][1] = ((*msgchar) << 4) >> 4;         

 // THIS IS TO CHECK BUSY FLAG BEFORE CONTINUE

 PORTB = (PORTB | 0b00110000); // ENABLE=1 R/W=1
 PORTD = (PORTD & 0b01000011); 
 DDRD = (DDRD & 0b11000011); // RS = OUTPUT, PIN 7  DATABITS INPUT, PINS 2,3,4,5
 
 while (bitON(PORTD,5)){
// WAIT UNTIL BUSY FLAG IS 0
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=1
delayNanos(500);
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=1 
delayNanos(200);} 

PORTB = (PORTB & 0b11101111); // ENABLE=1 R/W=0
DDRD = (DDRD | 0b00111100); // RS = OUTPUT, PIN 7  DATABITS OUTPUT, PINS 2,3,4,5

PORTD = (PORTD | 0b10000000) | charBits [i][0]<<2 ; // RS= 1 WRITE DATA HIGH BITS;
delayNanos(500);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = ((PORTD | 0b10000000) & 0b11000011)| charBits [i][1]<<2 ; // RS= 1 D7=1 WRITE DATA LOW BITS;
delayNanos(500);
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);
      }

PORTB = (PORTB & 0b11011111) | 0b00010000; // ENABLE=0 R/W=1
PORTD = (PORTD & 0b01000011); // DATA BUS LOW RS= 0;
_delay_us(50);
PORTD = PORTD | 0b00111100 ;   // PULL UP RESISTOR INPUT MODE 
DDRD = DDRD & 0b11000011 ; // RS = OUTPUT, PIN 7  DATABITS INPUT, PINS 2,3,4,5
     
}

void displaySecondLine (char text[]){




    char * msgchar = & text[0];

    uint8_t charBits [sizeof(text)-1][1];

    uint8_t center = (16 - (sizeof(text)-1))/2+63 ; // IN SECOND LINE DDRAM ADDRESS START IN 40 HEXA OR 64 DECIMAL THIS WILL BE FIRS MEMORY POSITION

    // THIS IS TO CHECK BUSY FLAG BEFORE CONTINUE

PORTB = (PORTB | 0b00110000); // ENABLE=1 R/W=1
PORTD = (PORTD & 0b01000011); 
 
while (bitON(PORTD,5)){
// WAIT UNTIL BUSY FLAG IS 0
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500);
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
delayNanos(500); 
} 

PORTB = (PORTB & 0b11101111); // ENABLE=1 R/W=0
DDRD = (DDRD | 0b00111100); // RS = OUTPUT, PIN 7  DATABITS OUTPUT, PINS 2,3,4,5

PORTD = ((PORTD | 0b00100000) & 0b01100011)| (center>>4)<<2 ; // RS= 0 D7=1 WRITE ADDRESSS OF START MEMORY HIGH BITS;
delayNanos(500); 
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500); 


PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0       
PORTD = (PORTD & 0b01000011)| ((center<<4)>>4)<<2 ; // RS= 0 WRITE ADDRESSS OF START MEMORY LOW BITS;
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(200); 

uint8_t i=0;
uint8_t z=sizeof(text)-1;
for (i=0; i<z; i++){
msgchar+=i;
charBits [i][0] = (*msgchar) >> 4;
charBits [i][1] = ((*msgchar) << 4) >> 4;       

 // THIS IS TO CHECK BUSY FLAG BEFORE CONTINUE

 PORTB = (PORTB | 0b00110000); // ENABLE=1 R/W=1
 PORTD = (PORTD & 0b01000011); 
 DDRD = (DDRD & 0b11000011); // RS = OUTPUT, PIN 7  DATABITS INPUT, PINS 2,3,4,5
 
 while (bitON(PORTD,5)){
// WAIT UNTIL BUSY FLAG IS 0
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500); 
PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
delayNanos(500); 
 
} 

PORTB = (PORTB & 0b11101111); // ENABLE=1 R/W=0
DDRD = (DDRD | 0b00111100); // RS = OUTPUT, PIN 7  DATABITS OUTPUT, PINS 2,3,4,5

PORTD = (PORTD | 0b10000000) | charBits [i][0]<<2 ; // RS= 1 WRITE DATA HIGH BITS;
delayNanos(500); 
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500); 

PORTB = PORTB | 0b00100000 ; // ENABLE=1 R/W=0 
PORTD = ((PORTD | 0b10000000) & 0b11000011)| charBits [i][1]<<2 ; // RS= 1 D7=1 WRITE DATA LOW BITS;
delayNanos(500); 
PORTB = PORTB & 0b11011111 ; // ENABLE=0 R/W=0
delayNanos(500); 

      }

PORTB = (PORTB & 0b11011111) | 0b00010000; // ENABLE=0 R/W=1
PORTD = (PORTD & 0b01000011); // DATA BUS LOW RS= 0;
_delay_us(50);
PORTD = PORTD | 0b00111100 ;   // PULL UP RESISTOR INPUT MODE 
DDRD = DDRD & 0b11000011 ; // RS = OUTPUT, PIN 7  DATABITS INPUT, PINS 2,3,4,5
     

}
int main(void)
{
// ENABLE GLOBAL INTERRUPTS
sei();

operationMode('H');
displayFirtLine ("Hola");
displaySecondLine ("Es una prueba");

}

THE MAKEFILE

# make file simple can be more complicated

lcd_direct_manipulation.hex: lcd_direct_manipulation.elf
	avr-objcopy -O ihex lcd_direct_manipulation.elf lcd_direct_manipulation.hex

lcd_direct_manipulation.o: main.c C:\WinAVR-20100110\avr\include\avr\io.h C:\WinAVR-20100110\avr\include\avr\interrupt.h C:\WinAVR-20100110\avr\include\util\delay.h
	avr-gcc -g -Os -DF_CPU=16000000UL -mmcu=atmega328p -Wall -Wextra -pedantic -c -o lcd_direct_manipulation.o lcd_direct_manipulation.c

lcd_direct_manipulation.elf: lcd_direct_manipulation.o
	avr-gcc -o lcd_direct_mainpulation.elf lcd_direct_manipulation.o

flash: 
	avrdude -F -v -p atmega328p -b57600 -c arduino -P COM4 -D -U flash:w:lcd_direct_manipulation.hex:i

clean:
	rm -rf *.o *.hex *.elf

# -V dissable verificacion of upload comprared with the file. I don't use it. Make faster upload.

# -F dissable device signature

# -D dissable autoerase fr flash. Atmega328p can erase by page. description don't mention if autoerase erase eeprom.  

# -v verbose output

docdoc · May 14, 2025, 3:17pm

Please edit your post above (do NOT create a new post, using the little pencil button at the bottom of your post), select the code and press the "<CODE/>" icon in the toolbar to mark it as code.
If not, the forum "interprets" some characters of the sketch and therefore not only the formatting is lost, but the code is no longer correctly readable and it is not possible to copy it, and we can't give you any practical advice.

Geek_Emeritus · May 14, 2025, 3:19pm

did you adjust the brightness by attaching a 5k pot to positive voltage and the brightness pin? typically pin 3, Contrast

gilshultz · May 14, 2025, 3:28pm

Sorry I cannot follow your word schematic, can you post an annotated one? Show all connections, power sources, and grounds. 100 Ohm pot is to low to work and will probably fry, depending on its wattage.

DVDdoug · May 14, 2025, 3:35pm

All I can tell you is that it's NOT a pull-up problem.

Pull-ups are SOMETIMES needed on INPUTS. But the inputs to your LCD are (presumably) connected to Arduino outputs. And an Arduino output is always "forced" high or low. It never "floats" (when configured as an output) so there's never a need for a pull-up on whatever is connected to one of its outputs.

lobos_dario · May 14, 2025, 4:23pm

I used two 10.k resistors divider,I will check with a potentiometer 10 k. As I read value should be 4.7 k for a good result. But this is not the problem only appears first line I set and LCD library example set 16 x 2. Entry mode and and resistors pull up have the same bits. Depends on Ext bit of function set. In Hitachi datasheet this is not mentioned but in ST7070 yes. I have to try this.

lobos_dario · May 14, 2025, 4:24pm

In 4 bit mode 4 are disconnected this is my concern about it.

xfpd · May 14, 2025, 4:39pm

Hello @lobos_dario

lobos_dario · May 14, 2025, 4:56pm

Connections are in the code. Cables are checked with a tester from the top of the nano pin to the pin of the LCD no bad connection. I seen some same issues in the web with no connection problems. I used also example of LCD library with the used connection showing the same problem. I will buy a 10 k potentiometer but only shows only line and is set to 16 x 2 so contrast is not the problem because second line is disabled.

lobos_dario · May 14, 2025, 4:59pm

Pull up in voltage LCD controller defines the signal wave brightness and contrast depending on duty cycle and wave voltages. I am not sure which of three pull ups are better in this case and maybe a bad setting disable it so no wave signal will have if no external resistors have the circuit. The controller is with a plastic black on it so I don't know exactly which one it is.

This is the datasheet explanation:

https://drive.google.com/file/d/1EQaa9kTp2FsJuegxwTxgaiT7awEoMsvJ/view?usp=drivesdk

https://drive.google.com/file/d/1EUGiz4xFTWN6ae5Oteb8voL4pkIm3WbV/view?usp=drivesdk

xfpd · May 14, 2025, 5:06pm

What is this and how is it wired? Show a wiring diagram and a picture to verify.

Your code does not send anything to the LCD.

TomGeorge · May 14, 2025, 5:44pm

Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.

Can you post some images of your project?
So we can see your component layout.

Thanks.. Tom....

van_der_decken · May 14, 2025, 5:56pm

I'm sure you took a quick read through of the component's datasheet (in this case, the HD44780U) beforehand

and saw that the only input pin without a dedicated pullup is the E pin.

PaulRB · May 14, 2025, 6:08pm

Right now, you don't know if the problem is faulty code or faulty hardware.

So forget using your own code until you have the example code from your LCD library working.

When this works, that will prove that your wiring is correct and that your LCD and Arduino are not faulty.

Then you can test your code, knowing that if it does not work, the problem must be that code and not something else.

lobos_dario · May 14, 2025, 6:38pm

The display show white boxes (not black) like all these

I used my code and example. Show only one line both despite is supposed to be settled as 16 x 2 . That is the same command to define resistors in extended mode

PaulRB · May 14, 2025, 6:43pm

Sorry, but I'm having difficulties understanding you.

For example:

How can both of these be true?

These words make no sense at all. Please try using Google translate to turn your replies into English.

xfpd · May 14, 2025, 6:56pm

Blue background, white text - OP screen

Green background, black text - search results

noiasca · May 14, 2025, 7:26pm

Yes this can be a problem.

Please post a link to the exact ST7070 display you have bought - and furthermore - post a link to the complete datasheet of the display you are using.

I'm familiar with the ST7070 display driver. MY ST7070 display offers a Serial and a parallel port. If you jumper the display incorrectly - the display will not display anything.

If you need a working library for the ST7070 you can use mine:

But it is essential that you have the correct display, have activated the correct interface and the correct wiring.

PaulRB · May 14, 2025, 7:33pm

Thanks @xfpd !

@lobos_dario 16X2 LCD are available in two types, "positive" and "negative". The LCD and it's driver chips are identical for each type. The difference is in the other layers in the display, such as the polarising filter, and whether the screen has a backlight or not. These differences determine whether the text appears dark against a lighter background or the text appears bright against a dark background.

A problem with the wiring, code or a faulty display will result in black or white boxes depending on the type of display. But in truth it is the same problem.

So do not be concerned that you see black boxes and not white boxes. It is the same underlying problem.

hallowed31 · May 14, 2025, 8:50pm

Does yours have a little contrast adjustment pot built in on the back? Mine all do, just use a small screwdriver to play around with it until it looks the way you want.

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