PB2

Also, sorry about the squash thing - I'm not a professional software developer. Thank you for the insights, I'm learning a lot!

I looked over everything and it looks good. Since you know the new source code better, you should update the examples. I'll do the acceptance testing on my hardware and...

Trying to compile `uart_tx_file.ino` for `Arduino Mega or Mega 2560` and I get the following error: ``` Arduino: 1.8.12 (Windows 10), TD: 1.52, Board: "Arduino Mega or Mega 2560, ATmega2560...

Thanks, everything compiles fine now - UART: Working 100% - SPI: RX sketches are completely unresponsive - I2C: RX sketches are completely unresponsive I'll look into what might be going...

### I2C: While the TwoWire class inherits from the Stream class, there are a couple of TwoWire members needed for access by this library. These required members include: ```C++ //...

> Do you really need the `onReceive` function? I mean the way it has been implemented it doesn't matter at all when the data has been received. Yes, I've done...

We also need to add another board ([ESP8266](https://arduino.stackexchange.com/a/34500/61572)) to the following processor exclusion conditions and readme disclaimer: https://github.com/PowerBroker2/SerialTransfer/blob/64fc4ea01cd972c8fef514a58267ecb9ffc971b7/src/SPITransfer.h#L5 https://github.com/PowerBroker2/SerialTransfer/blob/64fc4ea01cd972c8fef514a58267ecb9ffc971b7/src/SPITransfer.cpp#L3

I've more or less decided to forge on ahead improving the master branch since I couldn't easily grasp what exactly is being updated with this PR. However, that doesn't mean...

> Thanks a lot for asking, that is nice of you. I am using this library for one of my projects, to transfer photos (roughly 100kb in size) via UART....

This lib seems to be unsupported. A much easier to use and supported serial packet library can be found [here](https://github.com/PowerBroker2/SerialTransfer).