SoftwareSerial dependency removed. Upgraded to support C++11

[mohake-keshavarzi]

By using a Stream you can support both hardware and software serial while having the same functionality. By the way, the initialization of the serial interface should be handled by the user himself which is not a complicated task and offers more flexibility. Also, the Arduino library manager conflicts with adding the library due to this dependency, at least for me 🙂.

After brute-forcing the library to my Arduino IDE, I received some "type mismatch" errors regarding casting integer values to enum ones. It seems that You were using an older version of Arduino C++ compiler which allows such a thing but with more recent versions such a cast should be done explicitly through a static_cast function. I also handled this issue in my Fork.

I am planning to create a new branch, continue the development of the library, and test it on my setup which consists of an ESP32-based LILYGO T-Display and a SIM900A Mini V3.8.2. module. I will use software serial in my project.

[nthnn]

Hi! I have just finished reviewing your PR. First and foremost, thank you for pointing out things that I have overlooked in this library before releasing it to the Arduino Library Manager.

... continue the development of the library, and test it on my setup which consists of an ESP32-based LILYGO T-Display ...

Speaking of, upon development, I just tested this library with Arduino UNO. Never tested it on other boards with different compiler toolchains. While the compiler for ESP32 and ESP8266 boards have low tolerance on errors and warnings, I think (but I might be mistaken). So yeah, again, I overlooked.

Lastly, I'll rebuild the Doxygen documentation for this library then make another release to make the changes available to the Arduino Library Manager.

I'll merge this PR now. Thanks again! Very much appreciated.