lcd4bit.c - Character LCD interface example¶
Demonstrates a Character LCD using the industry standard parallel interface in 4-bit mode. Assumes a 5V LCD; digital-only IO pins are assumed to be used for the four-bit data bus because they are 5V input tolerant.
Tested with Optrex 24227 and Optrex DMC-50448N-AAE-AD. Should work with any LCD that uses the Hitachi HD44780 LCD controller.
#include "pic24_all.h"
REMAP THE LCD module pins based on the target system
#if (HARDWARE_PLATFORM == EMBEDDED_C1)
# define RS_HIGH() (_LATC2 = 1)
# define RS_LOW() (_LATC2 = 0)
# define CONFIG_RS() CONFIG_RC2_AS_DIG_OUTPUT()
# define RW_HIGH() (_LATC1 = 1)
# define RW_LOW() (_LATC1 = 0)
# define CONFIG_RW() CONFIG_RC1_AS_DIG_OUTPUT()
# define E_HIGH() (_LATC0 = 1)
# define E_LOW() (_LATC0 = 0)
# define CONFIG_E() CONFIG_RC0_AS_DIG_OUTPUT()
# define LCD4O (_LATC4)
# define LCD5O (_LATC5)
# define LCD6O (_LATC6)
# define LCD7O (_LATC7)
# define LCD7I (_RC7)
# define CONFIG_LCD4_AS_INPUT() CONFIG_RC4_AS_DIG_INPUT()
# define CONFIG_LCD5_AS_INPUT() CONFIG_RC5_AS_DIG_INPUT()
# define CONFIG_LCD6_AS_INPUT() CONFIG_RC6_AS_DIG_INPUT()
# define CONFIG_LCD7_AS_INPUT() CONFIG_RC7_AS_DIG_INPUT()
# define CONFIG_LCD4_AS_OUTPUT() CONFIG_RC4_AS_DIG_OUTPUT()
# define CONFIG_LCD5_AS_OUTPUT() CONFIG_RC5_AS_DIG_OUTPUT()
# define CONFIG_LCD6_AS_OUTPUT() CONFIG_RC6_AS_DIG_OUTPUT()
# define CONFIG_LCD7_AS_OUTPUT() CONFIG_RC7_AS_DIG_OUTPUT()
#elif (HARDWARE_PLATFORM == EMBEDDED_F14)
# define RS_HIGH() (_LATC12 = 1)
# define RS_LOW() (_LATC12 = 0)
# define CONFIG_RS() CONFIG_RC12_AS_DIG_OUTPUT()
# define RW_HIGH() (_LATD11 = 1)
# define RW_LOW() (_LATD11 = 0)
# define CONFIG_RW() CONFIG_RD11_AS_DIG_OUTPUT()
# define E_HIGH() (_LATD10 = 1)
# define E_LOW() (_LATD10 = 0)
# define CONFIG_E() CONFIG_RD10_AS_DIG_OUTPUT()
# define LCD4O (_LATE4)
# define LCD5O (_LATE5)
# define LCD6O (_LATE6)
# define LCD7O (_LATE7)
# define LCD7I (_RE7)
# define CONFIG_LCD4_AS_INPUT() CONFIG_RE4_AS_DIG_INPUT()
# define CONFIG_LCD5_AS_INPUT() CONFIG_RE5_AS_DIG_INPUT()
# define CONFIG_LCD6_AS_INPUT() CONFIG_RE6_AS_DIG_INPUT()
# define CONFIG_LCD7_AS_INPUT() CONFIG_RE7_AS_DIG_INPUT()
# define CONFIG_LCD4_AS_OUTPUT() CONFIG_RE4_AS_DIG_OUTPUT()
# define CONFIG_LCD5_AS_OUTPUT() CONFIG_RE5_AS_DIG_OUTPUT()
# define CONFIG_LCD6_AS_OUTPUT() CONFIG_RE6_AS_DIG_OUTPUT()
# define CONFIG_LCD7_AS_OUTPUT() CONFIG_RE7_AS_DIG_OUTPUT()
#else
# 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 E_HIGH() (_LATB14 = 1)
# define E_LOW() (_LATB14 = 0)
# define CONFIG_E() CONFIG_RB14_AS_DIG_OUTPUT()
# define LCD4O (_LATB5)
# define LCD5O (_LATB6)
# define LCD6O (_LATB7)
# define LCD7O (_LATB8)
# define LCD7I (_RB8)
# define CONFIG_LCD4_AS_INPUT() CONFIG_RB5_AS_DIG_INPUT()
# define CONFIG_LCD5_AS_INPUT() CONFIG_RB6_AS_DIG_INPUT()
# define CONFIG_LCD6_AS_INPUT() CONFIG_RB7_AS_DIG_INPUT()
# define CONFIG_LCD7_AS_INPUT() CONFIG_RB8_AS_DIG_INPUT()
# 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()
#endif
#define GET_BUSY_FLAG() (LCD7I)
/**
Functions above this line must be redefined for
your particular PICmicro-to-LCD interface
*/
//Configure 4-bit data bus for output
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
}
//Configure 4-bit data bus for input
void configBusAsInLCD(void) {
CONFIG_LCD4_AS_INPUT(); //D4
CONFIG_LCD5_AS_INPUT(); //D5
CONFIG_LCD6_AS_INPUT(); //D6
CONFIG_LCD7_AS_INPUT(); //D7
RW_HIGH(); // R/W = 1, for read
}
//Output lower 4-bits of u8_c to LCD data lines
void outputToBusLCD(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
}
//Configure the control lines for the LCD
void configControlLCD(void) {
CONFIG_RS(); //RS
CONFIG_RW(); //RW
CONFIG_E(); //E
RW_LOW();
E_LOW();
RS_LOW();
}
//Pulse the E clock, 1 us delay around edges for
//setup/hold times
void pulseE(void) {
DELAY_US(1);
E_HIGH();
DELAY_US(1);
E_LOW();
DELAY_US(1);
}
Write a byte (u8_Cmd) to the LCD. u8_DataFlag is ‘1’ if data byte, ‘0’ if command byte u8_CheckBusy is ‘1’ if must poll busy bit before write, else simply delay before write u8_Send8Bits is ‘1’ if must send all 8 bits, else send only upper 4-bits
void writeLCD(uint8_t u8_Cmd, uint8_t u8_DataFlag,
uint8_t u8_CheckBusy, uint8_t u8_Send8Bits) {
uint8_t u8_BusyFlag;
uint8_t u8_wdtState;
if (u8_CheckBusy) {
RS_LOW(); //RS = 0 to check busy
check busy
configBusAsInLCD(); //set data pins all inputs
u8_wdtState = _SWDTEN; //save WDT enable state
CLRWDT(); //clear the WDT timer
_SWDTEN = 1; //enable WDT to escape infinite wait
do {
E_HIGH();
DELAY_US(1); // read upper 4 bits
u8_BusyFlag = GET_BUSY_FLAG();
E_LOW();
DELAY_US(1);
pulseE(); //pulse again for lower 4-bits
} while (u8_BusyFlag);
_SWDTEN = u8_wdtState; //restore WDT enable state
} else {
DELAY_MS(10); // don't use busy, just delay
}
configBusAsOutLCD();
if (u8_DataFlag) RS_HIGH(); // RS=1, data byte
else RS_LOW(); // RS=0, command byte
outputToBusLCD(u8_Cmd >> 4); // send upper 4 bits
pulseE();
if (u8_Send8Bits) {
outputToBusLCD(u8_Cmd); // send lower 4 bits
pulseE();
}
}
Initialize the LCD, modify to suit your application and LCD
void initLCD() {
DELAY_MS(50); //wait for device to settle
writeLCD(0x20,0,0,0); // 4 bit interface
writeLCD(0x28,0,0,1); // 2 line display, 5x7 font
writeLCD(0x28,0,0,1); // repeat
writeLCD(0x06,0,0,1); // enable display
writeLCD(0x0C,0,0,1); // turn display on; cursor, blink is off
writeLCD(0x01,0,0,1); // clear display, move cursor to home
DELAY_MS(3);
}
//Output a string to the LCD
void outStringLCD(char *psz_s) {
while (*psz_s) {
writeLCD(*psz_s, 1, 1,1);
psz_s++;
}
}
int main (void) {
configBasic(HELLO_MSG); // Set up heartbeat, UART, print hello message and diags
configControlLCD(); //configure the LCD control lines
initLCD(); //initialize the LCD
outStringLCD("******Hello, my name is Bob********");
writeLCD(0xC0,0,1,1); // cursor to 2nd line
outStringLCD("-----these lines are moving!-------");
while (1) {
writeLCD(0x18,0,1,1); // shift left
DELAY_MS(200);
doHeartbeat();
}
}