diff --git a/examples/MassStorage/msc_external_flash/.skip.txt b/examples/MassStorage/msc_external_flash/.skip.txt
index f8e761cb..66aeeee1 100644
--- a/examples/MassStorage/msc_external_flash/.skip.txt
+++ b/examples/MassStorage/msc_external_flash/.skip.txt
@@ -1,2 +1,3 @@
 pico_rp2040_tinyusb_host
 CH32V20x_EVT
+feather_rp2040_tinyusb
diff --git a/examples/MassStorage/msc_external_flash_sdcard/.skip.txt b/examples/MassStorage/msc_external_flash_sdcard/.skip.txt
index f8e761cb..66aeeee1 100644
--- a/examples/MassStorage/msc_external_flash_sdcard/.skip.txt
+++ b/examples/MassStorage/msc_external_flash_sdcard/.skip.txt
@@ -1,2 +1,3 @@
 pico_rp2040_tinyusb_host
 CH32V20x_EVT
+feather_rp2040_tinyusb
diff --git a/examples/MassStorage/msc_sdfat/.skip.txt b/examples/MassStorage/msc_sdfat/.skip.txt
index a0185409..77a312c7 100644
--- a/examples/MassStorage/msc_sdfat/.skip.txt
+++ b/examples/MassStorage/msc_sdfat/.skip.txt
@@ -1 +1,2 @@
 pico_rp2040_tinyusb_host
+feather_rp2040_tinyusb
diff --git a/src/arduino/Adafruit_USBD_CDC.cpp b/src/arduino/Adafruit_USBD_CDC.cpp
index 893db83e..afe27d5f 100644
--- a/src/arduino/Adafruit_USBD_CDC.cpp
+++ b/src/arduino/Adafruit_USBD_CDC.cpp
@@ -27,11 +27,15 @@
 // esp32 use built-in core cdc
 #if CFG_TUD_CDC && !defined(ARDUINO_ARCH_ESP32)
 
+// Include before "Arduino.h" because TinyUSB is part of platform cores
+// When developing TinyUSB, it needs to include the local version, not the
+// platform core version, which is what gets included by Arduino.h
+#include "Adafruit_USBD_CDC.h"
+
 #include "Arduino.h"
 
 #include "Adafruit_TinyUSB_API.h"
 
-#include "Adafruit_USBD_CDC.h"
 #include "Adafruit_USBD_Device.h"
 
 #ifndef TINYUSB_API_VERSION
@@ -170,6 +174,40 @@ int Adafruit_USBD_CDC::dtr(void) {
   return tud_cdc_n_connected(_instance);
 }
 
+bool Adafruit_USBD_CDC::rts(void) {
+  return tud_cdc_n_get_line_state(_instance) & CDC_CONTROL_LINE_STATE_RTS;
+}
+
+bool Adafruit_USBD_CDC::dsr(void) {
+  return tud_cdc_n_get_serial_state(_instance).dsr;
+}
+
+bool Adafruit_USBD_CDC::dcd(void) {
+  return tud_cdc_n_get_serial_state(_instance).dcd;
+}
+
+bool Adafruit_USBD_CDC::ri(void) {
+  return tud_cdc_n_get_serial_state(_instance).ri;
+}
+
+void Adafruit_USBD_CDC::dsr(bool c) {
+  cdc_serial_state_t serial_state = tud_cdc_n_get_serial_state(_instance);
+  serial_state.dsr = c;
+  tud_cdc_n_set_serial_state(_instance, serial_state);
+}
+
+void Adafruit_USBD_CDC::dcd(bool c) {
+  cdc_serial_state_t serial_state = tud_cdc_n_get_serial_state(_instance);
+  serial_state.dcd = c;
+  tud_cdc_n_set_serial_state(_instance, serial_state);
+}
+
+void Adafruit_USBD_CDC::ri(bool c) {
+  cdc_serial_state_t serial_state = tud_cdc_n_get_serial_state(_instance);
+  serial_state.ri = c;
+  tud_cdc_n_set_serial_state(_instance, serial_state);
+}
+
 Adafruit_USBD_CDC::operator bool() {
   if (!isValid()) {
     return false;
diff --git a/src/arduino/Adafruit_USBD_CDC.h b/src/arduino/Adafruit_USBD_CDC.h
index 9c0952f3..3fb61423 100644
--- a/src/arduino/Adafruit_USBD_CDC.h
+++ b/src/arduino/Adafruit_USBD_CDC.h
@@ -59,7 +59,21 @@ class Adafruit_USBD_CDC : public Stream, public Adafruit_USBD_Interface {
   uint8_t stopbits(void);
   uint8_t paritytype(void);
   uint8_t numbits(void);
-  int dtr(void);
+
+  // Flow control bit getters.
+  int dtr(void); // pre-existing, I don't want to change the return type.
+  bool rts(void);
+  // bool cts(void);  // NOT PART OF THE CDC ACM SPEC?!
+  bool dsr(void);
+  bool dcd(void);
+  bool ri(void);
+
+  // Flow control bit setters.
+  // void cts(bool c);  // NOT PART OF CDC ACM SPEC?!
+  void dsr(bool c);
+  void dcd(bool c);
+  void ri(bool c);
+  // Break is a little harder, it's an event, not a state.
 
   // Stream API
   virtual int available(void);
diff --git a/src/class/cdc/cdc.h b/src/class/cdc/cdc.h
index da490a6d..a5a5c5f8 100644
--- a/src/class/cdc/cdc.h
+++ b/src/class/cdc/cdc.h
@@ -412,6 +412,49 @@ typedef struct TU_ATTR_PACKED
 
 TU_VERIFY_STATIC(sizeof(cdc_line_control_state_t) == 2, "size is not correct");
 
+//--------------------------------------------------------------------+
+// Notifications
+//--------------------------------------------------------------------+
+
+typedef union TU_ATTR_PACKED {
+  struct {
+    uint16_t dcd         :1;
+    uint16_t dsr         :1;
+    uint16_t break_err   :1;
+    uint16_t ri          :1;
+    uint16_t frame_err   :1;
+    uint16_t parity_err  :1;
+    uint16_t overrun_err :1;
+    uint16_t             :9;
+  };
+  uint16_t state;
+} cdc_serial_state_t;
+
+TU_VERIFY_STATIC(sizeof(cdc_serial_state_t) == 2, "size is not correct");
+
+typedef struct TU_ATTR_PACKED {
+  tusb_notification_t header;
+  union {
+    cdc_serial_state_t serial_state;
+    // Add more Notification "Data" payloads here as more are implemented.
+  };
+} cdc_notify_struct_t;
+
+TU_VERIFY_STATIC(sizeof(cdc_notify_struct_t) == 10, "size is not correct");
+
+tu_static const cdc_notify_struct_t cdc_notify_serial_status = {
+  .header = {
+    .bmRequestType_bit = {
+      .recipient = TUSB_REQ_RCPT_INTERFACE,
+      .type = TUSB_REQ_TYPE_CLASS,
+      .direction = TUSB_DIR_IN,
+    },
+    .bNotification = CDC_NOTIF_SERIAL_STATE,
+    .wValue = 0,
+    .wLength = sizeof(cdc_serial_state_t),
+  }
+};
+
 TU_ATTR_PACKED_END  // End of all packed definitions
 TU_ATTR_BIT_FIELD_ORDER_END
 
diff --git a/src/class/cdc/cdc_device.c b/src/class/cdc/cdc_device.c
index 6fccab6d..0c439d59 100644
--- a/src/class/cdc/cdc_device.c
+++ b/src/class/cdc/cdc_device.c
@@ -59,6 +59,10 @@ typedef struct {
   // Bit 0:  DTR (Data Terminal Ready), Bit 1: RTS (Request to Send)
   uint8_t line_state;
 
+  // Notify host of flow control bits: DSR, DCD, RI, and some error flags.
+  cdc_serial_state_t serial_state;
+  bool serial_state_changed;
+
   /*------------- From this point, data is not cleared by bus reset -------------*/
   char wanted_char;
   TU_ATTR_ALIGNED(4) cdc_line_coding_t line_coding;
@@ -76,6 +80,7 @@ typedef struct {
   // Endpoint Transfer buffer
   CFG_TUSB_MEM_ALIGN uint8_t epout_buf[CFG_TUD_CDC_EP_BUFSIZE];
   CFG_TUSB_MEM_ALIGN uint8_t epin_buf[CFG_TUD_CDC_EP_BUFSIZE];
+  CFG_TUSB_MEM_ALIGN cdc_notify_struct_t epnotif_buf;
 } cdcd_interface_t;
 
 #define ITF_MEM_RESET_SIZE   offsetof(cdcd_interface_t, wanted_char)
@@ -115,6 +120,29 @@ static bool _prep_out_transaction (cdcd_interface_t* p_cdc) {
   }
 }
 
+bool _send_serial_state_notification(cdcd_interface_t *p_cdc) {
+  const uint8_t rhport = 0;
+
+  if (!p_cdc->serial_state_changed) {
+    // Nothing to do.
+    return true;
+  }
+
+  if (!usbd_edpt_claim(rhport, p_cdc->ep_notif)) {
+    // If claim failed, we're already in the middle of a transaction.
+    // cdcd_xfer_cb() will pick up this change.
+    return true;
+  }
+  
+  // We have the end point.  Build and send the notification.
+  p_cdc->serial_state_changed = false;
+  
+  p_cdc->epnotif_buf = cdc_notify_serial_status;
+  p_cdc->epnotif_buf.header.wIndex = p_cdc->itf_num;
+  p_cdc->epnotif_buf.serial_state = p_cdc->serial_state;
+  return usbd_edpt_xfer(rhport, p_cdc->ep_notif, (uint8_t *) &(p_cdc->epnotif_buf), sizeof(p_cdc->epnotif_buf));
+}
+
 //--------------------------------------------------------------------+
 // APPLICATION API
 //--------------------------------------------------------------------+
@@ -138,6 +166,19 @@ uint8_t tud_cdc_n_get_line_state(uint8_t itf) {
   return _cdcd_itf[itf].line_state;
 }
 
+cdc_serial_state_t tud_cdc_n_get_serial_state(uint8_t itf) {
+  return _cdcd_itf[itf].serial_state;
+}
+
+void tud_cdc_n_set_serial_state(uint8_t itf, cdc_serial_state_t serial_state) {
+  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
+  if (p_cdc->serial_state.state != serial_state.state) {
+    p_cdc->serial_state_changed = true;
+    p_cdc->serial_state = serial_state;
+    _send_serial_state_notification(p_cdc);
+  }
+}
+
 void tud_cdc_n_get_line_coding(uint8_t itf, cdc_line_coding_t* coding) {
   (*coding) = _cdcd_itf[itf].line_coding;
 }
@@ -437,10 +478,10 @@ bool cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_
   // Identify which interface to use
   for (itf = 0; itf < CFG_TUD_CDC; itf++) {
     p_cdc = &_cdcd_itf[itf];
-    if ((ep_addr == p_cdc->ep_out) || (ep_addr == p_cdc->ep_in)) break;
+    if ((ep_addr == p_cdc->ep_out) || (ep_addr == p_cdc->ep_in) || (ep_addr == p_cdc->ep_notif)) break;
   }
   TU_ASSERT(itf < CFG_TUD_CDC);
-
+  
   // Received new data
   if (ep_addr == p_cdc->ep_out) {
     tu_fifo_write_n(&p_cdc->rx_ff, p_cdc->epout_buf, (uint16_t) xferred_bytes);
@@ -479,7 +520,11 @@ bool cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_
     }
   }
 
-  // nothing to do with notif endpoint for now
+  // Notifications
+  if (ep_addr == p_cdc->ep_notif) {
+    // Send any changes that may have come in while sending the previous change.
+    return _send_serial_state_notification(p_cdc);
+  }
 
   return true;
 }
diff --git a/src/class/cdc/cdc_device.h b/src/class/cdc/cdc_device.h
index 463feedf..d5522028 100644
--- a/src/class/cdc/cdc_device.h
+++ b/src/class/cdc/cdc_device.h
@@ -70,6 +70,12 @@ bool tud_cdc_n_connected(uint8_t itf);
 // Get current line state. Bit 0:  DTR (Data Terminal Ready), Bit 1: RTS (Request to Send)
 uint8_t tud_cdc_n_get_line_state(uint8_t itf);
 
+// Get current serial state.
+cdc_serial_state_t tud_cdc_n_get_serial_state(uint8_t itf);
+
+// Set current serial state.
+void tud_cdc_n_set_serial_state(uint8_t itf, cdc_serial_state_t ser_state);
+
 // Get current line encoding: bit rate, stop bits parity etc ..
 void tud_cdc_n_get_line_coding(uint8_t itf, cdc_line_coding_t* coding);
 
@@ -132,6 +138,14 @@ TU_ATTR_ALWAYS_INLINE static inline uint8_t tud_cdc_get_line_state(void) {
   return tud_cdc_n_get_line_state(0);
 }
 
+TU_ATTR_ALWAYS_INLINE static inline cdc_serial_state_t tud_cdc_get_serial_state(void) {
+  return tud_cdc_n_get_serial_state(0);
+}
+
+TU_ATTR_ALWAYS_INLINE static inline void tud_cdc_set_serial_state(cdc_serial_state_t ser_state) {
+  tud_cdc_n_set_serial_state(0, ser_state);
+}
+
 TU_ATTR_ALWAYS_INLINE static inline void tud_cdc_get_line_coding(cdc_line_coding_t* coding) {
   tud_cdc_n_get_line_coding(0, coding);
 }
diff --git a/src/common/tusb_types.h b/src/common/tusb_types.h
index d9c6ea75..d05c75d2 100644
--- a/src/common/tusb_types.h
+++ b/src/common/tusb_types.h
@@ -491,6 +491,27 @@ typedef struct TU_ATTR_PACKED {
 
 TU_VERIFY_STATIC( sizeof(tusb_control_request_t) == 8, "size is not correct");
 
+
+typedef struct TU_ATTR_PACKED {
+  union {
+    struct TU_ATTR_PACKED {
+      uint8_t recipient :  5; ///< Recipient type tusb_request_recipient_t.
+      uint8_t type      :  2; ///< Request type tusb_request_type_t.
+      uint8_t direction :  1; ///< Direction type. tusb_dir_t
+    } bmRequestType_bit;
+
+    uint8_t bmRequestType;
+  };
+
+  uint8_t bNotification;
+  uint16_t wValue;
+  uint16_t wIndex;
+  uint16_t wLength;
+} tusb_notification_t;
+
+TU_VERIFY_STATIC( sizeof(tusb_notification_t) == 8, "size is not correct");
+
+
 TU_ATTR_PACKED_END  // End of all packed definitions
 TU_ATTR_BIT_FIELD_ORDER_END