Mbed EventQueue example 2: Serial Interrupt Callback and deferred printf()

main.cpp

// Execution of certain function in an ISR context is not safe. 
// For example, printf() in an interrupt context causes a Mutex error. 
// Using Mbed's EventQueue, you can defer execution of code from an interrupt context to a user context.
// More about EventQueue: https://os.mbed.com/docs/mbed-os/v5.15/tutorials/the-eventqueue-api.html

#include "mbed.h"

EventQueue *queue = mbed_event_queue(); // event queue
RawSerial pc(USBTX, USBRX);

void onDataReceived();

void myCallback() {
    char c = pc.getc();
    printf("received: %c\r\n", c);
    pc.attach(&onDataReceived, Serial::RxIrq);  // reattach interrupt
}

void onDataReceived() {
    pc.attach(NULL, Serial::RxIrq); // detach interrupt
    queue->call(myCallback);        // process in a different context
}

int main() {
    pc.attach(&onDataReceived, Serial::RxIrq);
    queue->dispatch_forever();
}