How to communicate with LCD (Embedded C)

Question

I'm trying to get an arduino running C Code for a LCD display. Compiling and transmitting and executing C code works fine, tried some LED flashing. All wires should be OK too, when using the 'native' Arduino Library for LCD displays, everything works great, so it must be a code error I can't find :(

I'm trying to communicate with the LCD via 4 data-wire mode. Control and data pins are on the same port.

Here's the code:

//CPU-Clock Frequency
#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>

// Definitions:

#define LED_PIN PB5 //PB5 = Arduino Pin 13 (with LED)

#define COMPARE_REG OCR0A
#define TIMER_PIN OC0A
#define TIMER_CONTROL_REGISTER TCCR0A

#define LCD_PORT PORTD
#define LCD_PORTDIR DDRD
//controlpins:
#define RS_PIN PD0
#define RW_PIN PD1
#define ENABLE_PIN PD2
//datapins:
#define DB_7 PD7
#define DB_6 PD6
#define DB_5 PD5
#define DB_4 PD4

//Defined command parameters
#define CLEAR 0x01

// Methods
void sleep(uint16_t sleepTime){
for(;sleepTime>0;sleepTime--){ _delay_ms(1);}
}
void lcd_enable(){
LCD_PORT |= (1<<ENABLE_PIN);
//TODO: wait for busy?
sleep(5);
LCD_PORT &= !(1<<ENABLE_PIN);
sleep(5);
}

void lcd_pushOut(unsigned int data){
LCD_PORT &= (0x0F);
LCD_PORT |= (data & 0xF0);
lcd_enable();
LCD_PORT &= (0x0F);
LCD_PORT |= (data & 0x0F) << 4;
lcd_enable();
}

void lcd_command(unsigned int command){
unsigned short int tmp = (LCD_PORT & 0x0F); //speichere alte Steuerleitungen
LCD_PORT &= !(1<<RS_PIN);
lcd_pushOut(command);
LCD_PORT |= (1<<RS_PIN);
LCD_PORT |= tmp; //setze Steuerleitungen zurück
}

void lcd_init(){
sleep(15); //wait for LCD init
LCD_PORTDIR = 0xFF; //make port of LCD output.
LCD_PORT &= !(1<<RW_PIN); //write, dont read.
LCD_PORT |= (3<<4); //write '3' to port.
LCD_PORT &= !(1<<RS_PIN); //we give commands, not data!
lcd_enable();
sleep(1);
lcd_enable(); //write '3' to port 2nd time.
LCD_PORT &= 0x0F; //behalte steuersignale bei, setze daten'port' zurück.
LCD_PORT |= (2<<4); //write '2' to port.
lcd_enable();
//from now on LCD is in 4 bit mode.
lcd_pushOut(0x28); // 4 bit, 5x7 pix, 2 line mode
lcd_pushOut(0x06); //cursor rückt weiter, display scrollt
lcd_pushOut(0x0F); //display ein, cursor aus, blinken aus
lcd_pushOut(0x80); //we will write to DDRAM
lcd_pushOut(0x01); //clear display
//begin test writing zeroes.

LCD_PORT |= (1<<RS_PIN); //give data, not commands!
}

void timer_init(){
//DDRA |= (1<<TIMER_PIN); //make timerpin output.
TIMER_CONTROL_REGISTER = 0b10000000; //set timerpin high @bottom, on compare match clear. (0x80)
COMPARE_REG = 256/2; // dutycycle= 50%
}

void setTimerPower(unsigned int percent){   //set PWM Output (high) in %
COMPARE_REG = (percent/100) * 256;
}

int main (void)
{
//INIT
lcd_init();
//timer_init();
while(1){
lcd_command(CLEAR);
}
//now ready to write! let's write 3 zeroes!
lcd_pushOut('0');
lcd_pushOut('0');
lcd_pushOut('0');
/*
sleep(5000);
char c = '0';
while (1) {
lcd_clear();
lcd_pushOut(c++);
sleep(969); // 3x lcd_enable + 1 ms bearbeitungszeit? ... ziemlich großzügig
if(c > 0x7A) //entspricht c > 'z'
c='0';
}
*/
return 0;
}

EDIT: most of the time, LCD just makes black squares all over the first line.

You should include your code in your question instead of in a link. — skrrgwasme

Brian Sidebotham Brian Sidebotham · Accepted Answer · 2014-11-06T21:08:59

All instances of !(1<<BIT_NUMBER) should be converted to ~(1<<BIT_NUMBER) as ! is a boolean NOT and you're essentially doing !(true) so you get 0 as a result.

Example showing the problem (on x86):

int main( int argc, char* argv[] )
{
    printf( "%8.8X %8.8X\n", !(1<<2), ~(1<<2) );
    return 0;
}

And output is:

00000000 FFFFFFFB

Change that and you'll at least be further ahead. You should also state which controller is on the LCD to help any further.

How to communicate with LCD (Embedded C)

1 Answers