Fixes the hardware cdc jtag plugged/unplugged status and related timeout/delay (#9275)

* feat(hw_cdc):fixes the hardware cdc jtag plugged/unplugged status

This will use a new IDF 5.1 feature to detect if the USB HW CDC is plugged or not. This can be checked testing HWCDCSerial.
It also fixes issues related to timeout or delays while writing to the HW Serial when USB is unplugged.

* feat(usb): Creates HWSerial_Events.ino example

* feat: adds .skip.esp32

Skips the ESP32 SoC test given that it has no USB

* feat: adds .skip.esp32s2

Skips the ESP32S2 because it has no HW CDC JTAG interface

* fix: fixes issues with Ubuntu CI 

Only compiles the example in case it is using Hardware CD and JTAG mode.

* feat(serialcdc): non block functions

modifies write and flush to do not clock in case CDC host is not connected to the CDC client from the C3/S3/C6/H2

* fix(HWCDC): changes made demands testing for CDC ON BOOT

* feat(hwcdc): Improves HWSerial_Events.ino

Improves the example by adding more information about USB being plugged and CDC being connected.

* feat(hwcdc): solves CDC connection issue

Detects correctly when CDC is or not connected. 
Deals with USB unplugged while the sketch is printing to CDD.

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Update cores/esp32/HWCDC.cpp

* Apply suggestions from code review

---------

Co-authored-by: Lucas Saavedra Vaz <32426024+lucasssvaz@users.noreply.github.com>

Author: SuGlider

cores/esp32/HWCDC.cpp

@@ -1,4 +1,4 @@
-// Copyright 2015-2020 Espressif Systems (Shanghai) PTE LTD
+// Copyright 2015-2024 Espressif Systems (Shanghai) PTE LTD
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -28,19 +28,19 @@
 #include "hal/usb_serial_jtag_ll.h"
 #pragma GCC diagnostic warning "-Wvolatile"
 #include "rom/ets_sys.h"
+#include "driver/usb_serial_jtag.h"
 
 ESP_EVENT_DEFINE_BASE(ARDUINO_HW_CDC_EVENTS);
 
 static RingbufHandle_t tx_ring_buf = NULL;
 static QueueHandle_t rx_queue = NULL;
 static uint8_t rx_data_buf[64] = {0};
 static intr_handle_t intr_handle = NULL;
-static volatile bool initial_empty = false;
 static SemaphoreHandle_t tx_lock = NULL;
+static volatile bool isConnected = false;
 
-// workaround for when USB CDC is not connected
-static uint32_t tx_timeout_ms = 0;
-static bool tx_timeout_change_request = false;
+// timeout has no effect when USB CDC is unplugged
+static uint32_t requested_tx_timeout_ms = 100;
 
 static esp_event_loop_handle_t arduino_hw_cdc_event_loop_handle = NULL;
 
@@ -78,21 +78,17 @@ static void hw_cdc_isr_handler(void *arg) {
 
     if (usbjtag_intr_status & USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY) {
         // Interrupt tells us the host picked up the data we sent.
+        if(!usb_serial_jtag_is_connected()) {
+            isConnected = false;
+            usb_serial_jtag_ll_clr_intsts_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+            // USB is unplugged, nothing to be done here
+            return;
+        } else {
+            isConnected = true;
+        }
         if (usb_serial_jtag_ll_txfifo_writable() == 1) {
             // We disable the interrupt here so that the interrupt won't be triggered if there is no data to send.
             usb_serial_jtag_ll_disable_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
-            if(!initial_empty){
-                initial_empty = true;
-                // First time USB is plugged and the application has not explicitly set TX Timeout, set it to default 100ms.
-                // Otherwise, USB is still unplugged and the timeout will be kept as Zero in order to avoid any delay in the
-                // application whenever it uses write() and the TX Queue gets full.
-                if (!tx_timeout_change_request) {
-                    tx_timeout_ms = 100;
-                }
-                //send event?
-                //ets_printf("CONNECTED\n");
-                arduino_hw_cdc_event_post(ARDUINO_HW_CDC_EVENTS, ARDUINO_HW_CDC_CONNECTED_EVENT, &event, sizeof(arduino_hw_cdc_event_data_t), &xTaskWoken);
-            }
             size_t queued_size;
             uint8_t *queued_buff = (uint8_t *)xRingbufferReceiveUpToFromISR(tx_ring_buf, &queued_size, 64);
             // If the hardware fifo is avaliable, write in it. Otherwise, do nothing.
@@ -102,7 +98,7 @@ static void hw_cdc_isr_handler(void *arg) {
                 usb_serial_jtag_ll_write_txfifo(queued_buff, queued_size);
                 usb_serial_jtag_ll_txfifo_flush();
                 vRingbufferReturnItemFromISR(tx_ring_buf, queued_buff, &xTaskWoken);
-                usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+                if(isConnected) usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
                 //send event?
                 //ets_printf("TX:%u\n", queued_size);
                 event.tx.len = queued_size;
@@ -124,18 +120,15 @@ static void hw_cdc_isr_handler(void *arg) {
                 break;
             }
         }
-        //send event?
-        //ets_printf("RX:%u/%u\n", i, rx_fifo_len);
         event.rx.len = i;
         arduino_hw_cdc_event_post(ARDUINO_HW_CDC_EVENTS, ARDUINO_HW_CDC_RX_EVENT, &event, sizeof(arduino_hw_cdc_event_data_t), &xTaskWoken);
+        isConnected = true;
     }
 
     if (usbjtag_intr_status & USB_SERIAL_JTAG_INTR_BUS_RESET) {
         usb_serial_jtag_ll_clr_intsts_mask(USB_SERIAL_JTAG_INTR_BUS_RESET);
-        initial_empty = false;
-        usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
-        //ets_printf("BUS_RESET\n");
         arduino_hw_cdc_event_post(ARDUINO_HW_CDC_EVENTS, ARDUINO_HW_CDC_BUS_RESET_EVENT, &event, sizeof(arduino_hw_cdc_event_data_t), &xTaskWoken);
+        isConnected = false;
     }
 
     if (xTaskWoken == pdTRUE) {
@@ -144,12 +137,16 @@ static void hw_cdc_isr_handler(void *arg) {
 }
 
 static void ARDUINO_ISR_ATTR cdc0_write_char(char c) {
+    uint32_t tx_timeout_ms = 0;
+    if(usb_serial_jtag_is_connected()) {
+        tx_timeout_ms = requested_tx_timeout_ms;
+    }
     if(xPortInIsrContext()){
         xRingbufferSendFromISR(tx_ring_buf, (void*) (&c), 1, NULL);
     } else {
         xRingbufferSend(tx_ring_buf, (void*) (&c), 1, tx_timeout_ms / portTICK_PERIOD_MS);
     }
-    usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+    usb_serial_jtag_ll_txfifo_flush();
 }
 
 HWCDC::HWCDC() {
@@ -160,9 +157,33 @@ HWCDC::~HWCDC(){
     end();
 }
 
+
+// It should return <true> just when USB is plugged and CDC is connected.
 HWCDC::operator bool() const
 {
-    return initial_empty;
+    static bool running = false;
+
+    // USB may be unplugged
+    if (usb_serial_jtag_is_connected() == false) {
+        isConnected = false;
+        running = false;
+        return false;
+    }
+
+    if (isConnected) {
+        running = false;
+        return true;
+    }
+
+    if (running == false && !isConnected) { // enables it only once!
+        usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+    }
+    // this will feed CDC TX FIFO to trigger IN_EMPTY 
+    uint8_t c = '\0';
+    usb_serial_jtag_ll_write_txfifo(&c, sizeof(c));
+    usb_serial_jtag_ll_txfifo_flush();
+    running = true;
+    return false;
 }
 
 void HWCDC::onEvent(esp_event_handler_t callback){
@@ -206,9 +227,9 @@ void HWCDC::begin(unsigned long baud)
             log_e("HW CDC RX Buffer error");
         }
     }
-    //TX Buffer default has 256 bytes if not preset
+    //TX Buffer default has 16 bytes if not preset
     if (tx_ring_buf == NULL) {
-        if (!setTxBufferSize(256)) {
+        if (!setTxBufferSize(16)) {
             log_e("HW CDC TX Buffer error");
         }    
     }
@@ -227,8 +248,6 @@ void HWCDC::begin(unsigned long baud)
     } else {
         log_e("Serial JTAG Pins can't be set into Peripheral Manager.");
     }
-
-    usb_serial_jtag_ll_txfifo_flush();
 }
 
 void HWCDC::end()
@@ -248,13 +267,11 @@ void HWCDC::end()
         arduino_hw_cdc_event_loop_handle = NULL;
     }
     HWCDC::deinit(this);
+    isConnected = false;
 }
 
 void HWCDC::setTxTimeoutMs(uint32_t timeout){
-    tx_timeout_ms = timeout;
-    // it registers that the user has explicitly requested to use a value as TX timeout
-    // used for the workaround with unplugged USB and TX Queue Full that causes a delay on every write()
-    tx_timeout_change_request = true;
+    requested_tx_timeout_ms = timeout;
 }
 
 /*
@@ -278,9 +295,13 @@ size_t HWCDC::setTxBufferSize(size_t tx_queue_len){
 
 int HWCDC::availableForWrite(void)
 {
+    uint32_t tx_timeout_ms = 0;
     if(tx_ring_buf == NULL || tx_lock == NULL){
         return 0;
     }
+    if(usb_serial_jtag_is_connected()) {
+        tx_timeout_ms = requested_tx_timeout_ms;
+    }
     if(xSemaphoreTake(tx_lock, tx_timeout_ms / portTICK_PERIOD_MS) != pdPASS){
         return 0;
     }
@@ -289,11 +310,32 @@ int HWCDC::availableForWrite(void)
     return a;
 }
 
+static void flushTXBuffer()
+{
+    if (!tx_ring_buf) return;
+    UBaseType_t uxItemsWaiting = 0;
+    vRingbufferGetInfo(tx_ring_buf, NULL, NULL, NULL, NULL, &uxItemsWaiting);
+
+    size_t queued_size = 0;
+    uint8_t *queued_buff = (uint8_t *)xRingbufferReceiveUpTo(tx_ring_buf, &queued_size, 0, uxItemsWaiting);
+    if (queued_size && queued_buff != NULL) {
+        vRingbufferReturnItem(tx_ring_buf, (void *)queued_buff);
+    }
+    // flushes CDC FIFO
+    usb_serial_jtag_ll_txfifo_flush();
+}
+
 size_t HWCDC::write(const uint8_t *buffer, size_t size)
 {
+    uint32_t tx_timeout_ms = 0;
     if(buffer == NULL || size == 0 || tx_ring_buf == NULL || tx_lock == NULL){
         return 0;
     }
+    if(usb_serial_jtag_is_connected()) {
+        tx_timeout_ms = requested_tx_timeout_ms;
+    } else {
+        isConnected = false;
+    }
     if(xSemaphoreTake(tx_lock, tx_timeout_ms / portTICK_PERIOD_MS) != pdPASS){
         return 0;
     }
@@ -311,8 +353,9 @@ size_t HWCDC::write(const uint8_t *buffer, size_t size)
         to_send -= space;
         so_far += space;
         // Now trigger the ISR to read data from the ring buffer.
-        usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
-
+        usb_serial_jtag_ll_txfifo_flush();
+        if(isConnected) usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+ 
         while(to_send){
             if(max_size > to_send){
                 max_size = to_send;
@@ -325,9 +368,15 @@ size_t HWCDC::write(const uint8_t *buffer, size_t size)
             so_far += max_size;
             to_send -= max_size;
             // Now trigger the ISR to read data from the ring buffer.
-            usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+            usb_serial_jtag_ll_txfifo_flush();
+            if(isConnected) usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
         }
     }
+    // CDC is diconnected ==> flush all data from TX buffer
+    if(to_send && !usb_serial_jtag_ll_txfifo_writable()) {
+        isConnected = false;
+        flushTXBuffer();
+    }
     xSemaphoreGive(tx_lock);
     return size;
 }
@@ -339,21 +388,35 @@ size_t HWCDC::write(uint8_t c)
 
 void HWCDC::flush(void)
 {
+    uint32_t tx_timeout_ms = 0;
     if(tx_ring_buf == NULL || tx_lock == NULL){
         return;
     }
+    if(usb_serial_jtag_is_connected()) {
+        tx_timeout_ms = requested_tx_timeout_ms;
+    } else {
+        isConnected = false;
+    }
     if(xSemaphoreTake(tx_lock, tx_timeout_ms / portTICK_PERIOD_MS) != pdPASS){
         return;
     }
     UBaseType_t uxItemsWaiting = 0;
     vRingbufferGetInfo(tx_ring_buf, NULL, NULL, NULL, NULL, &uxItemsWaiting);
     if(uxItemsWaiting){
         // Now trigger the ISR to read data from the ring buffer.
-        usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
+        usb_serial_jtag_ll_txfifo_flush();
+        if(isConnected) usb_serial_jtag_ll_ena_intr_mask(USB_SERIAL_JTAG_INTR_SERIAL_IN_EMPTY);
     }
-    while(uxItemsWaiting){
+    uint8_t tries = 3;
+    while(tries && uxItemsWaiting){
         delay(5);
+        UBaseType_t lastUxItemsWaiting = uxItemsWaiting;
         vRingbufferGetInfo(tx_ring_buf, NULL, NULL, NULL, NULL, &uxItemsWaiting);
+        if (lastUxItemsWaiting == uxItemsWaiting) tries--;
+    }
+    if (tries == 0) {  // CDC isn't connected anymore...
+        isConnected = false;
+        flushTXBuffer();
     }
     xSemaphoreGive(tx_lock);
 }

libraries/ESP32/examples/HWSerial_Events/.skip.esp32

@@ -0,0 +1 @@
+

libraries/ESP32/examples/HWSerial_Events/.skip.esp32s2

@@ -0,0 +1 @@
+

libraries/ESP32/examples/HWSerial_Events/HWSerial_Events.ino

@@ -0,0 +1,94 @@
+/*
+ * This Example demonstrates how to receive Hardware Serial Events
+ * This USB interface is available for the ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2
+ * 
+ * It will log all events and USB status (plugged/unplugged) into UART0
+ * Any data read from UART0 will be sent to the USB CDC
+ * Any data read from USB CDC will be sent to the UART0
+ * 
+ * A suggestion is to use Arduino Serial Monitor for the UART0 port
+ * and some other serial monitor application for the USB CDC port
+ * in order to see the exchanged data and the Hardware Serial Events
+ * 
+ */
+
+#ifndef ARDUINO_USB_MODE
+#error This ESP32 SoC has no Native USB interface
+#elif ARDUINO_USB_MODE == 0
+#warning This sketch should be used when USB is in Hardware CDC and JTAG mode
+void setup(){}
+void loop(){}
+#else
+
+#if !ARDUINO_USB_CDC_ON_BOOT
+HWCDC HWCDCSerial;
+#endif
+
+#include "driver/usb_serial_jtag.h"
+
+// USB Event Callback Function that will log CDC events into UART0
+static void usbEventCallback(void* arg, esp_event_base_t event_base, int32_t event_id, void* event_data) {
+  if (event_base == ARDUINO_HW_CDC_EVENTS) {
+    switch (event_id) {
+      case ARDUINO_HW_CDC_CONNECTED_EVENT:
+        Serial0.println("CDC EVENT:: ARDUINO_HW_CDC_CONNECTED_EVENT");
+        break;
+      case ARDUINO_HW_CDC_BUS_RESET_EVENT:
+        Serial0.println("CDC EVENT:: ARDUINO_HW_CDC_BUS_RESET_EVENT");
+        break;
+      case ARDUINO_HW_CDC_RX_EVENT:
+        Serial0.println("\nCDC EVENT:: ARDUINO_HW_CDC_RX_EVENT");
+        // sends all bytes read from USB Hardware Serial to UART0
+        while (HWCDCSerial.available()) Serial0.write(HWCDCSerial.read());
+        break;
+      case ARDUINO_HW_CDC_TX_EVENT:
+        Serial0.println("CDC EVENT:: ARDUINO_HW_CDC_TX_EVENT");
+        break;
+
+      default:
+        break;
+    }
+  }
+}
+
+bool isPlugged() {
+  return usb_serial_jtag_is_connected();
+}
+
+const char* _hwcdc_status[] = {
+  " USB Plugged but CDC is not connected\r\n",
+  " USB Plugged and CDC is connected\r\n",
+  " USB Unplugged and CDC not connected\r\n",
+  " USB Unplugged BUT CDC is connected :: PROBLEM\r\n",
+};
+
+const char* HWCDC_Status() {
+  int i = isPlugged() ? 0 : 2;
+  if(HWCDCSerial) i += 1;
+  return _hwcdc_status[i];
+}
+
+void setup() {
+  Serial0.begin(115200);
+  Serial0.setDebugOutput(true);
+
+  HWCDCSerial.begin();
+  HWCDCSerial.onEvent(usbEventCallback);
+  Serial0.println("Starting...");
+}
+
+void loop() {
+  static uint32_t counter = 0;
+  
+  Serial0.print(counter);
+  Serial0.print(HWCDC_Status());
+
+  if (HWCDCSerial) {
+    HWCDCSerial.printf("  [%ld] connected\n\r", counter);
+  }
+  // sends all bytes read from UART0 to USB Hardware Serial
+  while (Serial0.available()) HWCDCSerial.write(Serial0.read());
+  delay(1000);
+  counter++;
+}
+#endif