add Serial rx callback function

[lshw]

example:

//return false drop char, bool rxcap(char ch) { if (ch == '1') { //if get char '1' Serial.println("callback!"); Serial.setRxCallBack(0); //disable CallBack return false; //del char '1' from rx buff } return true; }

void setup() { Serial.begin(115200); Serial.setRxCallBack(rxcap); }

void loop() { while(Serial.available()) Serial.write(Serial.read()); }

~

[MCUdude]

Care to explain what its intended purpose is? It doesn't seem to be a part of the official Arduino API, and your example doesn't quite show why it is useful.

[lshw]

This function can perform real-time operations, such as xon/xoff, or When avr uses multiple serial ports, use this function to realize that each serial port has a different size of receive buffer, or real-time mirroring from one serial port to another serial port, or can filter the received content first. refill the system's receive buffer,

[MCUdude]

Thanks for the explanation. Instead of submitting the PR here, please submit it to this repo instead. https://github.com/MCUdude/MCUdude_corefiles

MCUdude_corefiles are used as a submodule for MightyCore, MiniCore, MegaCore, and MajorCore.