'void（*）（const char *）'到'void（*）（）'[-fpermissive]

Question

I'm using this Arduino library to tokenize and parse commands received over a serial port but I have some strange pointer issue. I seen some other solution on stackoverflow(as suggested) but none of them helped me fix my issue.

Please let me know what I'm doing wrong with this addCommand function. Everything seems fine to me

Call pingHandler, pass "PING" character string to function definition & that's all.

#include <SoftwareSerial.h>
#include "SerialCommand.h"

SerialCommand sCmd;

void pingHandler (const char *command) {
  Serial.println("PONG");
}

void setup() {
  Serial.begin(9600);
  while (!Serial);

  sCmd.addCommand("PING", pingHandler);
}

void loop() {
  // put your main code here, to run repeatedly:
  if(Serial.available() > 0){
    sCmd.readSerial();
  }
}

I'm getting this error

C:\Users\GK_Desk_07\Documents\Arduino\ArduinoSerialCommand\ArduinoUnity\ArduinoUnity.ino: In function 'void setup()':

C:\Users\GK_Desk_07\Documents\Arduino\ArduinoSerialCommand\ArduinoUnity\ArduinoUnity.ino:13:38: warning: invalid conversion from 'void (*)(const char*)' to 'void (*)()' [-fpermissive]

   sCmd.addCommand("PING", pingHandler);

                                      ^

In file included from C:\Users\GK_Desk_07\Documents\Arduino\ArduinoSerialCommand\ArduinoUnity\ArduinoUnity.ino:2:0:

sketch\SerialCommand.h:84:8: note: initializing argument 2 of 'void SerialCommand::addCommand(const char*, void (*)())'

   void addCommand(const char *, void(*)());   // Add commands to processing dictionary

        ^

Answer 1

The definition for addCommand is

void addCommand(const char *, void(*)()); // Add commands to processing dictionary

So it expects a void(*)() (function without any arguments in C++, with any arbitrary arguments in C) but you're giving it a const char* argument

Change your pingHandler to

void pingHandler (void) {

Edit:

Since Arduino is C++ you don't need the void part inside parentheses

void pingHandler () {

Answer 2

The second argument of addCommand should be a pointer to a function taking no arguments , as shown in the example .

Try changing pingHandler to:

void pingHandler () {
  const char *command = sCmd.next();
  Serial.println("PONG");
}