Posible error en codigo

Hola amigos estoy realizando un proyecto para transmitir en 433mhz a traves de un Arduino Mini. Cuando trato de compilar el codigo me salen los siguientes errores:

C:\Users\USER\Documents\Arduino\sketch_feb09b\sketch_feb09b.ino: In function 'void loop()':

C:\Users\USER\Documents\Arduino\sketch_feb09b\sketch_feb09b.ino:122:39: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]

 sendmsg("VVV VVV VVV TESTING TESTING");

^

El Codigo:

// A simple uhf beacon using 433 mhz rf module
// credits to the author of the morse code generator
// more details on http://blog.riyas.org

struct t_mtab { char c, pat; } ;

struct t_mtab morsetab[] = {
 {'+', 42},   
 {'-', 97},
 {'=', 49},
 {'.', 106},
 {',', 115},
 {'?', 76},
 {'/', 41},
 {'A', 6},
 {'B', 17},
 {'C', 21},
 {'D', 9},
 {'E', 2},
 {'F', 20},
 {'G', 11},
 {'H', 16},
 {'I', 4},
 {'J', 30},
 {'K', 13},
 {'L', 18},
 {'M', 7},
 {'N', 5},
 {'O', 15},
 {'P', 22},
 {'Q', 27},
 {'R', 10},
 {'S', 8},
 {'T', 3},
 {'U', 12},
 {'V', 24},
 {'W', 14},
 {'X', 25},
 {'Y', 29},
 {'Z', 19},
 {'1', 62},
 {'2', 60},
 {'3', 56},
 {'4', 48},
 {'5', 32},
 {'6', 33},
 {'7', 35},
 {'8', 39},
 {'9', 47},
 {'0', 63}
} ;

#define N_MORSE  (sizeof(morsetab)/sizeof(morsetab[0]))
#define SPEED  (13) 
#define txpin    (13)
#define DOTLEN  (1200/SPEED)
#define DASHLEN  (3*(1200/SPEED))


void
dash()
{
  digitalWrite(txpin, HIGH);
  delay(DASHLEN);
  digitalWrite(txpin, LOW);
  delay(DOTLEN);
}

void
dit()
{
  digitalWrite(txpin, HIGH);
  delay(DOTLEN);
  digitalWrite(txpin, LOW);
  delay(DOTLEN);
}


void
send(char c)
{
  int i ;
  if (c == ' ') {
    delay(7*DOTLEN) ;
    return ;
  }
  for (i=0; i<N_MORSE; i++) {
    if (morsetab[i].c == c) {
      unsigned char p = morsetab[i].pat ;

      while (p != 1) {
          if (p & 1)
            dash() ;
          else
            dit() ;
          p = p / 2 ;
      }
      delay(2*DOTLEN) ;
 }
  Serial.print("?") ;
}
}


void
sendmsg(char *str)
{
  while (*str)
    send(*str++) ;
}


void
setup()
{                
  pinMode(txpin, OUTPUT);     
}

void 
loop() 
{
 sendmsg("VVV VVV VVV TESTING TESTING"); 
 delay(1500); //delay can be increased to save battery
}

Espero puedan ayudarme, gracias

Eso no es un error, es un warning o advertencia.
Yo lo compilé con DEVIOT y Platformio (ambiente similar) y no me dió errores ni advertencias.

AVR Memory Usage

Device: atmega328p

Program: 2036 bytes (6.2% Full)
(.text + .data + .bootloader)

Data: 298 bytes (14.6% Full)
(.data + .bss + .noinit)

avr-objcopy -O ihex -R .eeprom .pioenvs\uno\firmware.elf .pioenvs\uno\firmware.hex
[SUCCESS] Took 18.57 seconds

Muchas gracias!!!!!!

Esto fue lo que compilé, no sea cosa que mis ajustes hayan corregido alguna cosa

// A simple uhf beacon using 433 mhz rf module
// credits to the author of the morse code generator
// more details on http://blog.riyas.org

struct t_mtab { char c, pat; } ;

struct t_mtab morsetab[] = {
 {'+', 42},   
 {'-', 97},
 {'=', 49},
 {'.', 106},
 {',', 115},
 {'?', 76},
 {'/', 41},
 {'A', 6},
 {'B', 17},
 {'C', 21},
 {'D', 9},
 {'E', 2},
 {'F', 20},
 {'G', 11},
 {'H', 16},
 {'I', 4},
 {'J', 30},
 {'K', 13},
 {'L', 18},
 {'M', 7},
 {'N', 5},
 {'O', 15},
 {'P', 22},
 {'Q', 27},
 {'R', 10},
 {'S', 8},
 {'T', 3},
 {'U', 12},
 {'V', 24},
 {'W', 14},
 {'X', 25},
 {'Y', 29},
 {'Z', 19},
 {'1', 62},
 {'2', 60},
 {'3', 56},
 {'4', 48},
 {'5', 32},
 {'6', 33},
 {'7', 35},
 {'8', 39},
 {'9', 47},
 {'0', 63}
} ;

#define N_MORSE  (sizeof(morsetab)/sizeof(morsetab[0]))
#define SPEED  (13) 
#define txpin    (13)
#define DOTLEN  (1200/SPEED)
#define DASHLEN  (3*(1200/SPEED))


void dash() {
  digitalWrite(txpin, HIGH);
  delay(DASHLEN);
  digitalWrite(txpin, LOW);
  delay(DOTLEN);
}

void dit() {
  digitalWrite(txpin, HIGH);
  delay(DOTLEN);
  digitalWrite(txpin, LOW);
  delay(DOTLEN);
}


void send(char c) {
  int i ;
  if (c == ' ') {
    delay(7*DOTLEN) ;
    return ;
  }
  for (i=0; i<N_MORSE; i++) {
      if (morsetab[i].c == c) {
        unsigned char p = morsetab[i].pat ;

        while (p != 1) {
            if (p & 1)
              dash() ;
            else
              dit() ;
            p = p / 2 ;
        }
        delay(2*DOTLEN) ;
     }
     Serial.print("?") ;
  }
}


void
sendmsg(char *str)  {
  while (*str)
    send(*str++) ;
}


void setup() {                
  pinMode(txpin, OUTPUT);     
}

void loop() {
   sendmsg("VVV VVV VVV TESTING TESTING"); 
   delay(1500); //delay can be increased to save battery
}