Breaking ino files into .h files fails

Projects Programming
4

Hi @lexter333 ,

the Arduino IDE (unfortunately in this case :wink: ) takes care that functions defined later in a sketch are brought to the knowledge of the compiler early.

Usually a C/C++ programmer has to take care that the compiler knows the interface specification of a function (does it require parameters and if yes how many and which types).

If you put these two lines in front of your comms.h

void HelpersSendLEDIndication();
void HelpersReceiveLEDIndication();

before their first use the compiler will accept that they are defined later in the sketch.

This version compiles:

#pragma once

#define TXD1 19
#define RXD1 21

/**********************
****** LEDs ***********
***********************/
#define SendLED 16       //Send LED
#define ReceiveLED 17  //Receive LED

  // Use Serial1 for UART communication
  HardwareSerial mySerial(2);

void HelpersSendLEDIndication();
void HelpersReceiveLEDIndication();

//Called from the ino Setup
void HelpersSetup() {
  mySerial.begin(9600, SERIAL_8N1, RXD1, TXD1);  // UART setup
  Serial.println("ESP32 UART Receiver");
  pinMode(SendLED, OUTPUT);
  pinMode(ReceiveLED, OUTPUT);
  digitalWrite(SendLED, LOW);
  digitalWrite(ReceiveLED, LOW);
  delay(50);
  //flash both leds as an indication 
  HelpersSendLEDIndication();
  HelpersReceiveLEDIndication();
}

void HelpersSendLEDIndication(){ 
  for (int i = 0; i <= 3; i++) {
    digitalWrite(SendLED, HIGH);
    delay(100);
    digitalWrite(SendLED, LOW);
  }
}

void HelpersReceiveLEDIndication() {
  for (int i = 0; i <= 3; i++) {
    digitalWrite(ReceiveLED, HIGH);
    delay(100);
    digitalWrite(ReceiveLED, LOW);
  }
}

However as @gcjr wrote already in well written C/C++ you would (forward) declare the functions in an .h or .hpp file and provide the final declaration of the function in a .c or .cpp file.

The reason for this is that someone using your library does not need to know how the functions are programmed as long as he/she nows how to call a specific function from outside.

Good luck!
ec2021

P.S.: I included a "#pragma once" in the .h-file to make sure that it will only be included once in a single project (include guard).

If you are interested you may look here to see a very simple example of

comms.h split to .h and .cpp

Example sketch sketch.ino that makes use of comms.h:

/*
   Forum: https://forum.arduino.cc/t/breaking-ino-files-into-h-files-fails/1406752/4
   Wokwi: https://wokwi.com/projects/442462078146788353

*/

#include "comms.h"

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  HelpersSetup();
}

unsigned long lastS = 0;
unsigned long lastR = 0;

void loop() {
  if (millis() - lastS > 1000) {
    lastS = millis();
    HelpersSendLEDIndication();
  }
  if (millis() - lastR > 2000) {
    lastR = millis();
    HelpersReceiveLEDIndication();
  }

}

comms.h

#pragma once
#include "Arduino.h"

#define TXD1 19
#define RXD1 21

/**********************
****** LEDs ***********
***********************/
#define SendLED 16       //Send LED
#define ReceiveLED 17  //Receive LED

// Functions
void HelpersSendLEDIndication();
void HelpersReceiveLEDIndication();
void HelpersSetup();

comms.cpp

#pragma once
#include "comms.h"

  // Use Serial1 for UART communication
HardwareSerial mySerial(2);

//Called from the ino Setup
void HelpersSetup() {
  mySerial.begin(9600, SERIAL_8N1, RXD1, TXD1);  // UART setup
  Serial.println("ESP32 UART Receiver");
  pinMode(SendLED, OUTPUT);
  pinMode(ReceiveLED, OUTPUT);
  digitalWrite(SendLED, LOW);
  digitalWrite(ReceiveLED, LOW);
  delay(50);
  //flash both leds as an indication 
  HelpersSendLEDIndication();
  HelpersReceiveLEDIndication();
}

void HelpersSendLEDIndication(){ 
  for (int i = 0; i <= 3; i++) {
    digitalWrite(SendLED, HIGH);
    delay(100);
    digitalWrite(SendLED, LOW);
  }
}

void HelpersReceiveLEDIndication() {
  for (int i = 0; i <= 3; i++) {
    digitalWrite(ReceiveLED, HIGH);
    delay(100);
    digitalWrite(ReceiveLED, LOW);
  }
}

Feel free to check it out on https://wokwi.com/projects/442462078146788353

It is NOT very elaborated but demonstrates the principle use ...