- add CDC/serial_echo example using SerialTinyUSB

- call CDC flush in task() for core without tinyusb builtin support

Author: hathach

examples/CDC/serial_echo/.pico_rp2040_tinyusb_host.test.skip

@@ -0,0 +1,40 @@
+/*********************************************************************
+ Adafruit invests time and resources providing this open source code,
+ please support Adafruit and open-source hardware by purchasing
+ products from Adafruit!
+
+ MIT license, check LICENSE for more information
+ Copyright (c) 2019 Ha Thach for Adafruit Industries
+ All text above, and the splash screen below must be included in
+ any redistribution
+*********************************************************************/
+
+#include "Adafruit_TinyUSB.h"
+
+/* This sketch demonstrates USB CDC Serial echo (convert to upper case) using SerialTinyUSB which
+ * is available for both core with built-in USB support and without.
+ */
+
+void setup() {
+  // Manual begin() is required on core without built-in support e.g. mbed rp2040
+  if (!TinyUSBDevice.isInitialized()) {
+    TinyUSBDevice.begin(0);
+  }
+}
+
+void loop() {
+  #ifdef TINYUSB_NEED_POLLING_TASK
+  // Manual call tud_task since it isn't called by Core's background
+  TinyUSBDevice.task();
+  #endif
+
+  uint8_t buf[64];
+  uint32_t count = 0;
+  while (SerialTinyUSB.available()) {
+    buf[count++] = (uint8_t) toupper(SerialTinyUSB.read());
+  }
+
+  if (count) {
+    SerialTinyUSB.write(buf, count);
+  }
+}

examples/CDC/serial_echo/serial_echo.ino

@@ -25,13 +25,6 @@
 #ifndef ADAFRUIT_TINYUSB_H_
 #define ADAFRUIT_TINYUSB_H_
 
-// Core that has built-in support: Adafruit SAMD, nRF, rp2040, esp32
-#if !(defined(ARDUINO_ARCH_SAMD) || defined(ARDUINO_NRF52_ADAFRUIT) ||         \
-      defined(ARDUINO_ARCH_ESP32) ||                                           \
-      (defined(ARDUINO_ARCH_RP2040) && !defined(ARDUINO_ARCH_MBED)))
-#define TINYUSB_NEED_POLLING_TASK
-#endif
-
 // Error message for Core that must select TinyUSB via menu
 #if !defined(USE_TINYUSB) &&                                                   \
     (defined(ARDUINO_ARCH_SAMD) ||                                             \

src/Adafruit_TinyUSB.h

@@ -32,6 +32,13 @@
 // TinyUSB_API, USBD_CDC, USBD_Device, USBD_Interface,
 #define TINYUSB_API_VERSION 30000
 
+// Core that has built-in support: Adafruit SAMD, Adafruit nRF, rp2040, esp32
+#if !(defined(ARDUINO_ARCH_SAMD) || defined(ARDUINO_NRF52_ADAFRUIT) ||         \
+      defined(ARDUINO_ARCH_ESP32) ||                                           \
+      (defined(ARDUINO_ARCH_RP2040) && !defined(ARDUINO_ARCH_MBED)))
+#define TINYUSB_NEED_POLLING_TASK
+#endif
+
 //--------------------------------------------------------------------+
 // Core API
 // Should be called by BSP Core to initialize, process task

src/arduino/Adafruit_TinyUSB_API.h

@@ -150,7 +150,16 @@ uint8_t Adafruit_USBD_Device::addStringDescriptor(const char *s) {
   return index;
 }
 
-void Adafruit_USBD_Device::task(void) { tud_task(); }
+void Adafruit_USBD_Device::task(void) {
+  tud_task();
+
+#ifdef TINYUSB_NEED_POLLING_TASK
+  // can also be used with port with built-in support
+  if (SerialTinyUSB) {
+    SerialTinyUSB.flush();
+  }
+#endif
+}
 
 bool Adafruit_USBD_Device::mounted(void) { return tud_mounted(); }