(re)Implementing SMS reception interrupts

[Nastaliss]

Hi, I am quite new to this project and I came across #260 which was never merged back in 2019 but I think would be a great addition to this project.
I'm reusing @mayurharge 's changes and merging master into them.
I haven't yet tested the changes and they are still very much a work in progress :)

[mayurharge]

Hi, I am quite new to this project and I came across #260 which was never merged back in 2019 but I think would be a great addition to this project.
I'm reusing @mayurharge 's changes and merging master into them.
I haven't yet tested the changes and they are still very much a work in progress :)

Hey my sample codes might not work with Arduino Uno as i have used stm32bluepill for testing.

[Nastaliss]

I have only tested on a SIM800L module with an esp32 for now. Some tweaking of the example code was necessary but I made it work eventually!
I'll update these later.
I'll also take a look into the arduino uno, thanks for the heads up

[garudaonekh]

Unfortunately, I used SIM800L EVB V2(This board is great and solve the power issue). This board has no RINg PIN so there's no way to use this interrupt

[mayurharge]

Unfortunately, I used SIM800L EVB V2(This board is great and solve the power issue). This board has no RINg PIN so there's no way to use this interrupt

you need not to use the ring pin
please check read message without interrupt example https://github.com/mayurharge/TinyGSM/blob/master/examples/Read_SMS_message/Read_SMS_message.ino