Midi_USB_Host with a timer interrupt

[MichaelPNolan]

Just starting a thread because I'm investigating
https://github.com/khoih-prog/ESP32TimerInterrupt

if I set it up in Core0 the idea is that it will execute at a higher priority to make sure we don't lose notes. That way I can service the scope without suddenly finding that each loop in core0 task is just too slow.

Starting this thread before I have results to help document but also if there is feedback if anyone tried this or why it isn't going to work?

[MichaelPNolan]

I can certainly get the timer interrupt code to work inside the midi module but to make it do anything significant ... due to memory restrictions. Seems unlikely at this point, unless i bring the code from the library and make it memory resident but the library for usbh_midi is non-trivial.

For example to call this in the UsbMidi_Poll()

if (Midi.RecvData(&rcvd, bufMidi) == 0)

calls

/* Receive data from MIDI device */
uint8_t USBH_MIDI::RecvData(uint16_t *bytes_rcvd, uint8_t *dataptr)
{
        *bytes_rcvd = (uint16_t)epInfo[epDataInIndex].maxPktSize;
        uint8_t  r = pUsb->inTransfer(bAddress, epInfo[epDataInIndex].epAddr, bytes_rcvd, dataptr);
#ifdef EXTRADEBUG
        if( r )
                USBTRACE2("inTransfer():", r);
#endif
        if( *bytes_rcvd < (MIDI_EVENT_PACKET_SIZE-4)){
                dataptr[*bytes_rcvd]     = '\0';
                dataptr[(*bytes_rcvd)+1] = '\0';
        }
        return r;
}

which makes other calls ... so even if I was to fork usbh_midi.cpp and redesign it to operate with timer_interrupts i don't know that this is feasible given the constraints on how its memory resident and has to lock memory up with portENTER_CRITICAl_ISR and EXIT. Rapidly goes into "nah, its not going to work" space.

You'd really have to fully design the library

void IRAM_ATTR onTimer(){
    uint8_t bufMidi[MIDI_EVENT_PACKET_SIZE];
    uint16_t  rcvd;
    portENTER_CRITICAL_ISR(&timerMux);

   // if (Midi.RecvData(&rcvd,  bufMidi) == 0)
   // {
       Serial.println("midi data");//UsbMidi_Poll();
   // }
    portEXIT_CRITICAL_ISR(&timerMux);
}