trouble with interfacing 4x20 lcd to PIC24HJ64GP502

[pani212]

Hi

I am using microchip microstick which uses pic24hj64gp502. there are only 28 pins in the ic and for my application i can afford to use the lcd only in 4 bit mode. with my code i think there is some problem with initialization(i am not sure though). the clock that i am using is of 40MHz. all i can see flickering screen.
my code is as below:

#include "pic24_all.h"
#define RS_HIGH() _LATB9 = 1
#define RS_LOW() _LATB9 = 0
#define CONFIG_RS() CONFIG_RB9_AS_DIG_OUTPUT()
#define RW_HIGH() _LATB13 = 1
#define RW_LOW() _LATB13 = 0
#define CONFIG_RW() CONFIG_RB13_AS_DIG_OUTPUT()
#define En _LATB14
#define CONFIG_E() CONFIG_RB14_AS_DIG_OUTPUT()
#define LCD4O _LATB5
#define LCD5O _LATB6
#define LCD6O _LATB7
#define LCD7O _LATB8
#define LCD8 _LATB15


#define CONFIG_LCD4_AS_OUTPUT() CONFIG_RB5_AS_DIG_OUTPUT()
#define CONFIG_LCD5_AS_OUTPUT() CONFIG_RB6_AS_DIG_OUTPUT()
#define CONFIG_LCD6_AS_OUTPUT() CONFIG_RB7_AS_DIG_OUTPUT()
#define CONFIG_LCD7_AS_OUTPUT() CONFIG_RB8_AS_DIG_OUTPUT()
#define CONFIG_LCD8_AS_OUTPUT() CONFIG_RB15_AS_DIG_OUTPUT()


#define strobe() ((En=1),(En=0))

void configBusAsOutLCD(void)
{
RW_LOW(); //RW=0 to stop LCD from driving pins
CONFIG_LCD4_AS_OUTPUT(); //D4
CONFIG_LCD5_AS_OUTPUT(); //D5
CONFIG_LCD6_AS_OUTPUT(); //D6
CONFIG_LCD7_AS_OUTPUT(); //D7
}
void LCDbus(uint8_t u8_c)
{
LCD4O = u8_c & 0x01; //D4
LCD5O = (u8_c >> 1)& 0x01; //D5
LCD6O = (u8_c >> 2)& 0x01; //D6
LCD7O = (u8_c >> 3)& 0x01; //D7
}
void writeLCD(unsigned char c)
{
configBusAsOutLCD();
RS_HIGH();
LCDbus(c >>4);
strobe();
LCDbus(c);
strobe();
}

void initLCD()
{
RS_HIGH();
RW_LOW();
En =0;
DELAY_MS(50);
writeLCD(0x20); // 4 bit interface
DELAY_US(40);
writeLCD(0x28); // 2 line display, 5x7 font
DELAY_US(40);
writeLCD(0x06); // set entry mode
DELAY_US(40);
writeLCD(0x0E);
DELAY_US(40);
writeLCD(0x01); // clear display, move cursor to home
DELAY_MS(2);
}
void writeString(char *data)
{
RS_HIGH();
while(*data)
{
writeLCD(*data);
data++;
}
}

int main ()
{
configBasic(HELLO_MSG); // Set up heartbeat, UART, print hello message and diags
CONFIG_LCD8_AS_OUTPUT();

doHeartbeat();




initLCD(); //initialize the LCD

writeString("******Hello, my name is Bob********");
LCD8=1;
DELAY_MS(2000);
writeLCD(0xC0); // cursor to 2nd line

writeString("-----these lines are moving!-------");

while (1)
{
writeLCD(0x18); // shift left
DELAY_MS(200);
doHeartbeat();
}

return 0;
}

 

[horace1]

I found that timing is critical when writing LCDs otherwise you get nothing or it flickers
this code work for the Microchip Explorer 16 LCD

//Define LCD line position
#define LCD_Line1    0
#define LCD_Line2    40
#define LCD_Line3    80 


// LCD display ports etc
#define LCDdata PORTE //LATE					// data portE
#define LCDdataEnable	TRISE

#define E  LATDbits.LATD8   			// LCD E Clock RD9
#define Eenable TRISDbits.TRISD8

#define CS  LATDbits.LATD11   			// LCD chip select RD10
#define CSenable TRISDbits.TRISD11

#define RS LATDbits.LATD10				// LCD RS Register Select bit RD11
#define RSenable TRISDbits.TRISD10

#define RW LATDbits.LATD13				// read/write bit in LCDstatus RD12
#define RWenable TRISDbits.TRISD13

void lcd_delay() {int i; for(i=0;i<2;i++)  Nop();}// mSecDelay(2); }  // if LCD does not work make this longer

// Write instruction to the LCD
void writeInstruction(int LCDregister)
{
    //mSecDelay(2);					// delay for instruction
    // check if last instruction complete
    LCDdataEnable |= 0xff;          // set bits 0-7 input for data
    Nop();
    RW=1;
    Nop();
    RS=1;
    Nop();
    while(LCDdata &0x80)Nop();			// read bit of status
    LCDdataEnable &= 0x00;          // set bits 0-7 output for data
    RS=1;
    Nop()
    RW=0;
    Nop();
    LCDdata=LCDregister;			// set up instruction
    E=1;							// take clock E high 
	lcd_delay();
    E=0;
 }

// Write to register of the LCD
void writeDataRegister(int data)
{
    RS=0;
    Nop()
    RW=0;
    Nop()
    LCDdata=data & 0xff;
	lcd_delay();
    E=1;					// take clock E high 
	lcd_delay();
    E=0;
 }

// Write a register and data register value to the LCDs
void writeCommand(int LCDregister, int data)
{
 	writeInstruction(LCDregister);
    writeDataRegister(data);
}

void LCDcursor(int cursor)
{
	writeCommand(0x0A, cursor & 0xF);		// write lower addres
	writeCommand(0x0B, (cursor > 4) & 0xF);	// write upper addres
}

// write a data character byte to LCD
int lcdPutchar(int data)
{
    writeCommand(0x0C, data);
    return 1;
}




// Initialise the LCD 
void lcdInit()
{
	int i,data = 0;
    int m=128, n=240;
    int Hn=40;
    int Hp=n/Hn, Vp=m/16;
    int Nx=m;
    printf("m %d n %d Hn %d Hp %d Vp %d Nx %d\n",m , n , Hn , Hp , Vp , Nx );

	E=0;				// take E low
 	RS=0;				// Take RS pin low for command
 	RW=0;				// Take RS pin low for command
 	CS=0;				// Take CS pin low for command
    
    // set RS, RW and E bits as output
	Eenable =0;
	RSenable =0;
	RWenable =0;
	CSenable =0;
	
    LCDdataEnable = 0x00;          // set bits 0-7 output for data
  //  LCDdataEnable &= 0x0;          // set bits 0-3 output for data


 
  	writeCommand(0x0, 0x34);		// Set Mode: display ON, Master, blink on, cursor on, character mode internal CG
  	writeCommand(0x1, 0x75);	
  	writeCommand(0x2, 0x27);	
  	writeCommand(0x3, 0x7F);	
  	writeCommand(0x4, 0x07);	
  	writeCommand(8, 0x00);	
  	writeCommand(9, 0x00);	
  	writeCommand(10, 0x00);	
  	writeCommand(11, 0x00);	
	lcdClear();						// Clear LCD screen
	lcdHome();						// goto home position	
}

// move to line (1 or 2) at position >= 1
void lcdCursor(unsigned char line,unsigned char position)
{
    int cursor = 40*(line-1) + position-1;
  	writeCommand(0x0a,cursor);
  	writeCommand(0x0b,cursor>>8);
}

void lcdString(unsigned char line, unsigned char position, unsigned char *string)
{

	lcdCursor(line,position);
	while (*string)
	    lcdPutchar(*string++);

}