which is the best way to declare Serial while creating Arduino library?

Question

Well, I am trying make a library for HMI display. display and Arduino comminicate with Serial. So I will so many times Serial port. Generally I will use Serial.write commend. if I examine other libraries, there are lots way to declare serial. Why and which is the best I want to learn.

there I have seen declaring Serial methods.

Method 1

in library .h file

nothing

in library .cpp file

#include <SoftwareSerial.h>

SoftwareSerial SIM(RX_PIN,TX_PIN);

void KapadokyaGSM::basla(){
    SIM.begin(9600);
  _tampon.reserve(255);
}

Method 2

in library .h file

public:
EasyNex(HardwareSerial& serial);
...
private:
HardwareSerial* _serial;
...

in library .cpp file

EasyNex::EasyNex(HardwareSerial& serial){  // Constructor's parameter is the Serial we want to use
_serial = &serial;
}

void EasyNex::begin(unsigned long baud){
_serial->begin(baud);  // We pass the initialization data to the objects (baud rate) default: 9600
delay(100);            // Wait for the Serial to initialize

Also I have seen declaring with Stream but now i didnt find example codes. So finally Can anyone tell me what is the best for declearing Serial in library. it can be for only hardware serial or both

Answer 1

As regards the use of Stream:

I usually use Stream instead of HardwareSerial because:

• It allows the use of other serial devices, like SoftwareSerial or USBSerial that aren't "Hardware" UARTs.
• It even allows the use of non-serial systems, like sending data over networks or wireless devices

However it means:

• The user has to manually initialize their serial object / device as Stream has no facility for setting things like baud rates.

Answer 2

There is no best way, the first is using a global variable, being static. The second is dynamically (or at least to pass a serial instance).

It depends on your use

• If you want your code always to work with the same declared serial (hardware or serial) instance, you can use the first method, as it is the easiest.
• If you want your serial hardware port to be flexible (your code to work e.g. with a selectable hardware serial port on an Arduino Mega), you need the second.
• If you want to your serial port to be either software or hardware, you can use the second method, but you need another type (not the mentioned HardwareSerial class. I don't know by head the parent class of SoftwareSerial and HardwareSerial (The Stream class you mentioned could be a common parent class).