Wire.onReceive() function on Arduino - c++

Question

I am trying to take what is in this example given by the Arduino Wire library, and apply it to a program I am writing.
This is my code. The Comm.NDP[] statements are other class instances not saved in this file, so I believe you can ignore them.
**
* I2C.cpp handles sending of event messages
* between the LORA and MEGA via I2C protocol.
*/
#include "I2C.h"
#include "DATA.h"
#include "Globals.h"
#include <Wire.h>
#include <Arduino.h>
/**
* Constructor used to reference all other variables & functions.
*/
I2C::I2C() {
}
/**
* Assigns the proper address to the current micro controller.
*/
void I2C::initialize() {
//Sets the address for the current micro controller.
// Mega - 0
// LoRa - 1
Wire.begin(0);
Wire.setClock(8000000);
//Registers recieveEvent as a interrupt.
Wire.onReceive(receiveEvent); // register event
}
/**
* Receives byte over I2C Connection.
*/
static void receiveEvent(int howmany) {
//Iterator used below.
int i = 0;
for(i=0;i<120;i++) {
Comm.NDP[i] = ' ';
}
//Resets iterator.
i = 0;
//Checks to see if serial port is empty.
while (1 < Wire.available()) {
//Reads in single character from serial port.
char character = Wire.read();
NDP[i] = character;
i++;
}
Serial.println(Comm.NDP);
}
The example code from Arduino's Wire.h library
#include <Wire.h>
void setup() {
Wire.begin(8); // join i2c bus with address #8
Wire.onReceive(receiveEvent); // register event
Serial.begin(9600); // start serial for output
}
void loop() {
delay(100);
}
// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany) {
while (1 < Wire.available()) { // loop through all but the last
char c = Wire.read(); // receive byte as a character
Serial.print(c); // print the character
}
int x = Wire.read(); // receive byte as an integer
Serial.println(x); // print the integer
}
I am getting this error from the Arduino IDE.
error: invalid use of non-static member function
Wire.onReceive(receiveEvent); // register event
^
exit status 1
invalid use of non-static member function

Answer 1

You're missing declaration of receiveEvent before first use. Either move it's definition before begin or add there:
void receiveEvent(int howMany);