CCS/SW-EK-TM4C1294XL: Display value in 20x4 LCD with TM4C 1294XL

Krishnat Pawar said:

PLEASE SUGGEST POSSIBLE SOLUTION / POINT OUT ERRORS.

That's quite a task listing - is it not?

You do (neither) yourself - nor your helpers - any favor by electing, "4 Bit LCD Mode."     The "saving" of 4 GPIO is achieved at much greater SW complexity - and loss of display "robustness!"    (as ANY glitch upon "E" will throw the Lcd into complete disorder! ... i.e. the dual, "nibble" transfer sequence will be "unpaired.")

Your understanding of this vendor's most helpful API demands further review (especially GPIO Reads/Writes).     Here's (just one) example:

Krishnat Pawar said:

GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_5, 1);

While the use of "1" to "Set a Bit" is usual - it FAILS here!    Your review of the SW-DRL-User Guide reveals that the "3rd parameter must be the "bit-packed/valued" of the targeted bit."   (which is NOT "1" - instead GPIO_PIN_5 has the bit-packed value of 32.   Likewise "PIN_7 is 128, PIN_4 is 16, PIN_0 IS 1.)

There are bound to be even further code errors - yet your "retreat from the needless complexity demanded by "Four Bit LCD Mode" is paramount!

Your search of this forum will reveal my (multiple) past postings - some of which included the "Grandfather LCD Control IC's spec" - which revealed the complex Initialization Code and Timing.   Getting that (at all wrong) DOOMS all subsequent effort.

You note the Lcd's contrast pin as set to 3V3 - while possible - it is far more usual that the contrast pin is adjusted near GND - check your display's data sheet for the specifics.

Four Bit LCD Mode is (most properly) reserved for high volume Apps - and cannot justify the extra "time/attention" demanded - so that 4 GPIO are saved...  (for a limited volume usage...)

Hi Krishnat ,

 I think the best is for you to check on the logic analyzer if all the signals are properly generated to the LCD with respect to the timing requirements demanded by your LCD display. Check if the LCD has proper power supply and if you are manipulating the signals correctly. Below is a reference for how someone has done it in Raspberry Pi.

#!/usr/bin/python
#--------------------------------------
#    ___  ___  _ ____
#   / _ \/ _ \(_) __/__  __ __
#  / , _/ ___/ /\ \/ _ \/ // /
# /_/|_/_/  /_/___/ .__/\_, /
#                /_/   /___/
#
#  lcd_16x2.py
#  20x4 LCD Test Script with
#  backlight control and text justification
#
# Author : Matt Hawkins
# Date   : 06/04/2015
#
# www.raspberrypi-spy.co.uk/
#
#--------------------------------------
 
# The wiring for the LCD is as follows:
# 1 : GND
# 2 : 5V
# 3 : Contrast (0-5V)*
# 4 : RS (Register Select)
# 5 : R/W (Read Write)       - GROUND THIS PIN
# 6 : Enable or Strobe
# 7 : Data Bit 0             - NOT USED
# 8 : Data Bit 1             - NOT USED
# 9 : Data Bit 2             - NOT USED
# 10: Data Bit 3             - NOT USED
# 11: Data Bit 4
# 12: Data Bit 5
# 13: Data Bit 6
# 14: Data Bit 7
# 15: LCD Backlight +5V**
# 16: LCD Backlight GND
 
#import
import RPi.GPIO as GPIO
import time
 
# Define GPIO to LCD mapping
LCD_RS = 7
LCD_E  = 8
LCD_D4 = 25
LCD_D5 = 24
LCD_D6 = 23
LCD_D7 = 18
LED_ON = 15
 
# Define some device constants
LCD_WIDTH = 20    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False
 
LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line
 
# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005
 
def main():
  # Main program block
 
  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
  GPIO.setup(LCD_E, GPIO.OUT)  # E
  GPIO.setup(LCD_RS, GPIO.OUT) # RS
  GPIO.setup(LCD_D4, GPIO.OUT) # DB4
  GPIO.setup(LCD_D5, GPIO.OUT) # DB5
  GPIO.setup(LCD_D6, GPIO.OUT) # DB6
  GPIO.setup(LCD_D7, GPIO.OUT) # DB7
  GPIO.setup(LED_ON, GPIO.OUT) # Backlight enable
 
  # Initialise display
  lcd_init()
 
  # Toggle backlight on-off-on
  lcd_backlight(True)
  time.sleep(0.5)
  lcd_backlight(False)
  time.sleep(0.5)
  lcd_backlight(True)
  time.sleep(0.5)
 
  while True:
 
    # Send some centred test
    lcd_string("--------------------",LCD_LINE_1,2)
    lcd_string("Rasbperry Pi",LCD_LINE_2,2)
    lcd_string("Model B",LCD_LINE_3,2)
    lcd_string("--------------------",LCD_LINE_4,2)
 
    time.sleep(3) # 3 second delay
 
    lcd_string("Raspberrypi-spy",LCD_LINE_1,3)
    lcd_string(".co.uk",LCD_LINE_2,3)
    lcd_string("",LCD_LINE_3,2)
    lcd_string("20x4 LCD Module Test",LCD_LINE_4,2)
 
    time.sleep(3) # 20 second delay
 
    # Blank display
    lcd_byte(0x01, LCD_CMD)
 
    time.sleep(3) # 3 second delay
 
def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD) # 110011 Initialise
  lcd_byte(0x32,LCD_CMD) # 110010 Initialise
  lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
  lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
  lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
  lcd_byte(0x01,LCD_CMD) # 000001 Clear display
  time.sleep(E_DELAY)
 
def lcd_byte(bits, mode):
  # Send byte to data pins
  # bits = data
  # mode = True  for character
  #        False for command
 
  GPIO.output(LCD_RS, mode) # RS
 
  # High bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
    GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
    GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
    GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
    GPIO.output(LCD_D7, True)
 
  # Toggle 'Enable' pin
  lcd_toggle_enable()
 
  # Low bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
    GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
    GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
    GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
    GPIO.output(LCD_D7, True)
 
  # Toggle 'Enable' pin
  lcd_toggle_enable()
 
def lcd_toggle_enable():
  # Toggle enable
  time.sleep(E_DELAY)
  GPIO.output(LCD_E, True)
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)
  time.sleep(E_DELAY)
 
def lcd_string(message,line,style):
  # Send string to display
  # style=1 Left justified
  # style=2 Centred
  # style=3 Right justified
 
  if style==1:
    message = message.ljust(LCD_WIDTH," ")
  elif style==2:
    message = message.center(LCD_WIDTH," ")
  elif style==3:
    message = message.rjust(LCD_WIDTH," ")
 
  lcd_byte(line, LCD_CMD)
 
  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)
 
def lcd_backlight(flag):
  # Toggle backlight on-off-on
  GPIO.output(LED_ON, flag)
 
if __name__ == '__main__':
 
  try:
    main()
  except KeyboardInterrupt:
    pass
  finally:
    lcd_byte(0x01, LCD_CMD)
    lcd_string("Goodbye!",LCD_LINE_1,2)
    GPIO.cleanup()

Hi Charles,

Looking at this (Rasp) fellow's "LCD Init" - I do not believe it to be correct.    Improper initialization - as stated - DOOMS all subsequent efforts.
In addition - the "critical" contrast pin's level (Pin 3) - has been "unspecified!"     Attention to such detail IS required...   (throws all that follows under suspicion...)

The "lack of robustness" via 4-Bit Mode is little recognized - yet VERY REAL - and is employed in your presented example.   As you know - a clear Violation of KISS!    "Saving 4 GPIO - at risk of a highly disordered display screen" - proves an unsatisfactory, "Risk vs. Reward."

HI,

THANK YOU FOR SUPPORT.

CONNECTION:  VSS[PIN-1]-GND,  VDD[PIN-1]-5V,  VEE[PIN 3]-VARIABLE POT, RS[PIN 4]-PB4,  R/W[PIN 5]-GND,  EN[PIN 6]-PB5, DB0-DB3- N.C. D4-PE0,  D5-PE1,  D6-PE2,  D7-PE3,  A[PIN 15]-VARIABLE POT, A[PIN 16]-GND

#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/debug.h"
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"


void Initialize_LCD(void);
void string_to_lcd(unsigned char *s);
void LCD_write(unsigned char,unsigned int);


void main()
{
SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ | SYSCTL_OSC_MAIN | SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480), 120000000);
SysCtlDelay(100000);//2ms
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
SysCtlDelay(100000);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
SysCtlDelay(100000);
GPIOPinTypeGPIOOutput(GPIO_PORTE_BASE, GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);
SysCtlDelay(100000);
GPIOPinTypeGPIOOutput(GPIO_PORTB_BASE, GPIO_PIN_4|GPIO_PIN_5);
SysCtlDelay(100000);

GPIOPinWrite(GPIO_PORTE_BASE, GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3, 0x00);
SysCtlDelay(2000000);//20ms
Initialize_LCD();



LCD_write(0X80,0);
string_to_lcd("Hello");
LCD_write(0XC0,0);
string_to_lcd("TI E2E COMMUNITY");
LCD_write(0X94,0);
string_to_lcd("HI cb1 & Charles");
LCD_write(0XD4,0);
string_to_lcd("THANK YOU !!");
SysCtlDelay(0XFFFFFF00);

while(1){
}
}

void Initialize_LCD(void)
{
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_4, 0xEF); //RS PIN LOW
SysCtlDelay(5000);
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_5, 0xDF); //EN PIN LOW
SysCtlDelay(5000);

LCD_write(0x33,0);
SysCtlDelay(5000);
LCD_write(0x32,0);
SysCtlDelay(5000);
LCD_write(0x06,0);
SysCtlDelay(5000);
LCD_write(0x0E,0);
SysCtlDelay(5000);
LCD_write(0x28,0);
SysCtlDelay(5000);
LCD_write(0X01,0);
SysCtlDelay(10000000);
}

void LCD_write(unsigned char data,unsigned int RS)
{
if(RS==0)
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_4, 0xEF); //Cammand
else
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_4, 0xFF); //Data

SysCtlDelay(5000);
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_5, 0xFF);
SysCtlDelay(5000);

GPIOPinWrite(GPIO_PORTE_BASE, GPIO_PIN_3|GPIO_PIN_2|GPIO_PIN_1|GPIO_PIN_0, ((data & 0XF0)>>4));
SysCtlDelay(5000);
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_5, 0xDF);
SysCtlDelay(5000);

SysCtlDelay(5000);
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_5, 0xFF);
SysCtlDelay(5000);

GPIOPinWrite(GPIO_PORTE_BASE, GPIO_PIN_3|GPIO_PIN_2|GPIO_PIN_1|GPIO_PIN_0, (data & 0X0F));
SysCtlDelay(5000);
GPIOPinWrite(GPIO_PORTB_BASE, GPIO_PIN_5, 0xDF);
SysCtlDelay(5000);
}

void string_to_lcd(unsigned char *s)
{
unsigned int slen;
slen=strlen(s);
while(slen>0)
{
unsigned char D=*s;
LCD_write(*s,1);
SysCtlDelay(1000000);
slen--;
s++;
}

}