Help me fix an error in code for 74HC595 connecting to LCD

[mattycha]

Hi. I was going all over the internet to find an answer to my problem but I
couldn't find any so far. Some of you may have seen this in other forum. But
please understand me as I have tried so many things and asking many questions
but getting nowhere.

Then I came across this forum where there are many questions regarding on
74HC595 whereas other forums don't. So I am keeping my hopes high and
hopefully getting a solution to my problem.

What I am trying to do is that I do not have enough pins on my PIC18 so I want
to use 74HC595. Few has suggested to move on to other PIC which has more
I/O pins but I do not want to do that. Also using 74HC595 could be a good
learning experience for me.

I want to use 74HC595 to connect to LCD. I have set RS, RW, E pins for LCD and
have connected ST_CP, SH_CP, DS o 74HC595 correctly. Also, OE to GND and
MR to high. I think the problem is within my code but I cannot find anything
wrong with it. So could someone else please take a look at it? Maybe others can
pinpoint what and where it is wrong.

#include <p18f2455.h>
#include <delays.h>

#pragma config FOSC = HS
#pragma config WDT = OFF
#pragma config LVP = OFF
#pragma config BOR = OFF
#pragma config MCLRE = OFF

#define rs PORTBbits.RB2
#define rw PORTAbits.RA5
#define en PORTAbits.RA2		

#define DR PORTBbits.RB3   // connect it to pin 14 on 74HC595
#define SH_CP PORTBbits.RB6	// pin 11 on 74HC595
#define ST_CP PORTBbits.RB7	// pin 12 on 74HC595

void OutPORT(unsigned char data);
void sendData(unsigned char send); 
void writeData(unsigned char write); 
void writeString(const char rom *str); 
void READ(void);

void main(void)
{
	ADCON1 = 0xFF;
	// 74HC594
	TRISBbits.TRISB3 = 0;		// DR
	TRISBbits.TRISB6 = 0;		// SHCP
	TRISBbits.TRISB7 = 0;		// STCP

	 // LCD
                TRISBbits.TRISB2 = 0;
                TRISAbits.TRISA5 = 0;
                TRISAbits.TRISA2 = 0;
	rs = 0;
	rw = 0;
	en = 0;
	PORTB = 0;
	PORTA = 0;
	
	for(;;)
	{
		READ();
		writeString("Not working!!");
	}
}


void READ()
{
	Delay1KTCYx(250);          // Wait 20ms 
  	sendData(0x38);     
  	Delay1KTCYx(250);          // Wait 2ms 
  	sendData(0x0E);     // Turn LCD display off, cursor off and blinker off 
  	Delay1KTCYx(150);          // Wait 2ms 
  	sendData(0x01);     // Clear LCD display 
  	Delay1KTCYx(15);          // Wait 2ms 
  	sendData(0x06);       	
                Delay1KTCYx(15);         // Wait 2ms 
  	sendData(0x83); 			// start at line 1, position 3	
}

void sendData(unsigned char send) { 
        OutPORT(send);
        rs = 0; 
        rw = 0;
        en = 1; 
        Delay1KTCYx(1); 
        en = 0; 
} 

void writeData(unsigned char write) { 
        OutPORT(write); 
        rs = 1; 
        rw = 0;
        en = 1; 
        Delay1KTCYx(1); 
        en = 0; 
} 

void writeString(const char rom *str) { 
       while( *str ) { 
       writeData(*str); 
       str++;    
       } 
}

void OutPORT(unsigned char data) {
	unsigned char bits;
	for (bits=0x80; bits!=0; bits >> 1)
	{
		if ((bits & data) == bits)            // send DR
			DR = 1;
		else
			DR = 0;
		SH_CP = 1;			// clock SHCP
		SH_CP = 0;
	}
	ST_CP = 1;				// clock STCP
	ST_CP = 0;
}

I appreciate any help that I can get.
Thanks!!

p.s. I am using C18.

 

[laktronics]

lcd with 74hc595

Hi,
You need to give LCD busy delay after command (83) and in between chrs in the string, or you could have included the delay in send/write routines after EN signal is brought low. As regards HC595, things appear OK. You clould have used a 4bit interface directly using shift, store and serdata signal pins and r/w pin always grounded.

Regards,
Laktronics

 

[mattycha]

74hc595 & lcd

Strange... when I directly connected LCD to PIC, it worked fine without
delay line. Anyway, I did as you have suggested but still LCD wouldn't display
anything....

So you are sure that my inside my send/write function, there is no error in
calling outPORT function?

 

[laktronics]

74hc595 lcd

Hi,
Yah, I could n't find anything else wrong.

Regards,
Laktronics

Added after 26 minutes:

Hi,
In the out port,for loop, it should have been bits=0?
Regards,
Laktronics

 

[mattycha]

pic 74hc594

You mean this line?

Change this

if ((bits & data) == bits)

to

if ((bits & data) == 0)

??

I did that and it still do not work.....

Did anyone try to interface LCD with 74HC595 using C18??

 

[laktronics]

74hc595 lcd

Hi,
No, NO, I meant the following:

for (bits=0x80; bits!=0; bits >> 1)

Here you should use bits=0 instead of bits!=0
Regards,
Laktronics

 

[mattycha]

Re: 74HC595

hm... strange... nothing seems to work....
shoot.... i'm getting really really fraustrated.....

please help.... someone....

 

[lucafus]

Re: 74HC595

Hi mattycha.

Try this:

....
READ();
for(;
{
writeString("Not working!!");
}
...
In this way you initialize the LCD once.

....
void READ()
{
Delay1KTCYx(250); // Wait 20ms
sendData(0x38);
Delay1KTCYx(250); // Wait 2ms
sendData(0x0E); // Turn LCD display off, cursor off and blinker off
Delay1KTCYx(150); // Wait 2ms
sendData(0x06); // Sets mode to increment address by one
Delay1KTCYx(150); // Wait 2ms
sendData(0x01); // Clear LCD display
Delay1KTCYx(15); // Wait 2ms
sendData(0x06);
Delay1KTCYx(15); // Wait 2ms
sendData(0x83); // start at line 1, position 3
}
....

Are you using ICD2? Have you got a scope? If you have both, you can step the PIC and see if the outputs of the 74HC595 are as expected.

Luca.