Help needed: Arduino Wireless Notice Board project

[rafitc99]

@salmanfaris no any error, issue is in that LED metrix library print function parameters are *const char. So need to convert SMS boast string to const char *Variable.

[SAFVAN]

@kowshik1729 display is 16×32 P10 LED display.
RX and TX connected pin 3&2.
P10 connected as https://circuitdigest.com/microcontroller-projects/digital-notice-board-using-p10-led-matrix-display-and-arduino

[salmanfaris]

Hi @rafitc99, You can convert the string to char array using toCharArray() it will Copies the String’s characters to the supplied buffer.

• Syntax

myString.toCharArray(buf, len)

• Parameters
  myString: a variable of type String.
  buf: the buffer to copy the characters into. Allowed data types: array of char.
  len: the size of the buffer. Allowed data types: unsigned int.

more : https://www.arduino.cc/reference/en/language/variables/data-types/string/functions/tochararray/ , https://www.arduino.cc/en/Tutorial/BuiltInExamples#strings

also @SAFVAN is using const char* to hold message array You cannot change the contents of the location(s) this pointer points to.

[rafitc99]

@salmanfaris Rewrite all code and uploaded. But SMS is not displaying correctly in LED Board, .. I'm attaching code and display output. take a look ,

#include <SoftwareSerial.h>
#include <SPI.h>
#include <DMD.h>
#include <TimerOne.h>
#include "SystemFont5x7.h"
#include "Arial_black_16.h"

#define ROW 1
#define COLUMN 1
#define FONT Arial_Black_16

DMD led_module(ROW, COLUMN);

String st; 
const char *msg;
unsigned int LengMsg;
SoftwareSerial mySerial(3, 2);

void scan_module(){
  led_module.scanDisplayBySPI();
}

void setup() {
  Timer1.initialize(2000);
  Timer1.attachInterrupt(scan_module);
  led_module.clearScreen( true );
  
  Serial.begin(4800);
  mySerial.begin(4800);
  Serial.println("Starting..."); 
  delay(1000);
  mySerial.println("AT");
  pollSms();
  mySerial.println("AT+CMGF=1"); 
  pollSms();
  mySerial.println("AT+CNMI=1,2,0,0,0");
  pollSms();
}

void loop(){
  pollSms();
  delay(500);

  //Start print in led matrix 
  led_module.selectFont(FONT);
  led_module.drawMarquee(msg,LengMsg, (32 * ROW), 0);
  long start = millis();
  long timming = start;
  boolean flag = false;
  while (!flag){
    if((timming + 20) < millis()){
        flag = led_module.stepMarquee(-1, 0);
        timming = millis();
      }
    }
  }

void pollSms(){
  delay(500);
  while (Serial.available()) {
    mySerial.write(Serial.read());
    //String st = String(Serial.read());
    //Serial.println(st);
  }
  while(mySerial.available()) {
    Serial.write(mySerial.read());
    st = String(mySerial.readString());
    Serial.println(st);
    LengMsg = st.length();
    st.toCharArray(msg,LengMsg);    
  }
  delay(500);
}

output video : video link

[salmanfaris]

Can you print the SMS on the serial monitor too? so we can conclude the problem

[rafitc99]

@salmanfaris in serial monitor getting normal text. No problem in there.

[salmanfaris]

@rafitc99 Okay, it might be sending char from SMS buffer to LED panel. let me check, I'll get back to you.

[arunksoman]

@rafitc99 Please answer my question...

1. Why did u declared message as const? Const indicates you are not going to change that variable any more.

Try to use c_str() instead to_charArray()

Reference

[salmanfaris]

@rafitc99 , @SAFVAN did you tried the @arunksoman suggestion?

[SAFVAN]

Now message is displaying with mobile number, date, time.
I want filter the actual message only.