fix: HWCDC removed clearing USB Serial/JTAG interrupts during begin (#9316)

[kiran-desilva]

Description of Change

Fixes (#9316) where ESP may not respond over the USB Serial/JTAG interface if bytes are sent before HWCDC::begin(...) is called. Clearing of the interrupt status has been removed from HWCDC::begin(...) so that if the USB_SERIAL_JTAG_INTR_SERIAL_OUT_RECV_PKT is already set, the isr handler can process the interrupt status correctly.

Tests scenarios

Tested with ESP32-S3:

#include <Arduino.h>
#include <HWCDC.h>
#include <hal/usb_serial_jtag_ll.h>
#include <string>


uint32_t prevTime = 0;


void setup() {
  
  delay(5000);

  Serial.begin(115200);
  Serial.println("begin");
}

void loop() {

  if (millis() - prevTime > 500)
  {
    prevTime = millis();
    std::string output;
    output += "rxFifo: " + std::to_string(usb_serial_jtag_ll_rxfifo_data_available());
    output += " Serial avaliable: " + std::to_string(Serial.available());
    Serial.println(output.c_str());

  }

  while (Serial.available())
  {
    uint8_t b = Serial.read();
    Serial.print(Serial.available());
    Serial.print(" - ");
    Serial.write(b);
    Serial.println();
  }
  vTaskDelay(1); // watchdog
}

Related links

Closes (#9316)

[lucasssvaz]

I think this should be moved to the end method rather than being deleted, like it was done in #9331.

[kiran-desilva]

Do you mean end of the begin method or to the HWCDC::end()?

[lucasssvaz]

To HWCDC::end(). Check the PR I've linked

[SuGlider]

The fix of removing CLR INTR is the most important one.
LGTM.