diff --git a/src/class/audio/audio_device.c b/src/class/audio/audio_device.c
index 7df1777736..6c972ca7a1 100644
--- a/src/class/audio/audio_device.c
+++ b/src/class/audio/audio_device.c
@@ -520,10 +520,10 @@ static bool audiod_rx_xfer_isr(uint8_t rhport, audiod_function_t* audio, uint16_
   TU_VERIFY(tu_fifo_write_n(&audio->ep_out_ff, audio->lin_buf_out, n_bytes_received));
 
   // Schedule for next receive
-  TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_out, audio->lin_buf_out, audio->ep_out_sz), false);
+  TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_out, audio->lin_buf_out, audio->ep_out_sz, true));
   #else
   // Data is already placed in EP FIFO, schedule for next receive
-  TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_out, &audio->ep_out_ff, audio->ep_out_sz), false);
+  TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_out, &audio->ep_out_ff, audio->ep_out_sz, true));
   #endif
 
   #if CFG_TUD_AUDIO_ENABLE_FEEDBACK_EP
@@ -580,10 +580,10 @@ static bool audiod_tx_xfer_isr(uint8_t rhport, audiod_function_t * audio, uint16
   #endif
   #if USE_LINEAR_BUFFER_TX
   tu_fifo_read_n(&audio->ep_in_ff, audio->lin_buf_in, n_bytes_tx);
-  TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_in, audio->lin_buf_in, n_bytes_tx));
+  TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_in, audio->lin_buf_in, n_bytes_tx, true));
   #else
   // Send everything in ISO EP FIFO
-  TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_in, &audio->ep_in_ff, n_bytes_tx));
+  TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_in, &audio->ep_in_ff, n_bytes_tx, true));
   #endif
 
   // Call a weak callback here - a possibility for user to get informed former TX was completed and data gets now loaded into EP in buffer
@@ -607,7 +607,7 @@ bool tud_audio_int_n_write(uint8_t func_id, const audio_interrupt_data_t *data)
   // Check length
   if (tu_memcpy_s(int_ep_buf[func_id].buf, sizeof(int_ep_buf[func_id].buf), data, sizeof(audio_interrupt_data_t)) == 0) {
     // Schedule transmit
-    TU_ASSERT(usbd_edpt_xfer(_audiod_fct[func_id].rhport, _audiod_fct[func_id].ep_int, int_ep_buf[func_id].buf, sizeof(int_ep_buf[func_id].buf)), 0);
+    TU_ASSERT(usbd_edpt_xfer(_audiod_fct[func_id].rhport, _audiod_fct[func_id].ep_int, int_ep_buf[func_id].buf, sizeof(int_ep_buf[func_id].buf), false));
   } else {
     // Release endpoint since we don't make any transfer
     usbd_edpt_release(_audiod_fct[func_id].rhport, _audiod_fct[func_id].ep_int);
@@ -619,7 +619,7 @@ bool tud_audio_int_n_write(uint8_t func_id, const audio_interrupt_data_t *data)
 
 #if CFG_TUD_AUDIO_ENABLE_EP_OUT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_EP
 // This function is called once a transmit of a feedback packet was successfully completed. Here, we get the next feedback value to be sent
-static inline bool audiod_fb_send(audiod_function_t *audio) {
+static inline bool audiod_fb_send(audiod_function_t *audio, bool is_isr) {
   bool apply_correction = (TUSB_SPEED_FULL == tud_speed_get()) && audio->feedback.format_correction;
   // Format the feedback value
   if (apply_correction) {
@@ -647,7 +647,7 @@ static inline bool audiod_fb_send(audiod_function_t *audio) {
   //              10.14    3            3          Linux, OSX
   //
   // We send 3 bytes since sending packet larger than wMaxPacketSize is pretty ugly
-  return usbd_edpt_xfer(audio->rhport, audio->ep_fb, (uint8_t *) audio->fb_buf, apply_correction ? 3 : 4);
+  return usbd_edpt_xfer(audio->rhport, audio->ep_fb, (uint8_t *) audio->fb_buf, apply_correction ? 3 : 4, is_isr);
 }
 #endif
 
@@ -1133,10 +1133,10 @@ static bool audiod_set_interface(uint8_t rhport, tusb_control_request_t const *p
   #endif
             // Schedule first transmit if alternate interface is not zero, as sample data is available a ZLP is loaded
   #if USE_LINEAR_BUFFER_TX
-            TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_in, audio->lin_buf_in, 0));
+            TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_in, audio->lin_buf_in, 0, false));
   #else
             // Send everything in ISO EP FIFO
-            TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_in, &audio->ep_in_ff, 0));
+            TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_in, &audio->ep_in_ff, 0, false));
   #endif
           }
 #endif// CFG_TUD_AUDIO_ENABLE_EP_IN
@@ -1152,9 +1152,9 @@ static bool audiod_set_interface(uint8_t rhport, tusb_control_request_t const *p
 
             // Prepare for incoming data
   #if USE_LINEAR_BUFFER_RX
-            TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_out, audio->lin_buf_out, audio->ep_out_sz), false);
+            TU_VERIFY(usbd_edpt_xfer(rhport, audio->ep_out, audio->lin_buf_out, audio->ep_out_sz, false));
   #else
-            TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_out, &audio->ep_out_ff, audio->ep_out_sz), false);
+            TU_VERIFY(usbd_edpt_xfer_fifo(rhport, audio->ep_out, &audio->ep_out_ff, audio->ep_out_sz, false));
   #endif
           }
 
@@ -1164,7 +1164,7 @@ static bool audiod_set_interface(uint8_t rhport, tusb_control_request_t const *p
             audio->ep_fb = ep_addr;
             audio->feedback.frame_shift = desc_ep->bInterval - 1;
             // Schedule first feedback transmit
-            audiod_fb_send(audio);
+            audiod_fb_send(audio, false);
           }
   #endif
 #endif// CFG_TUD_AUDIO_ENABLE_EP_OUT
@@ -1472,7 +1472,7 @@ bool audiod_xfer_isr(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
     if (audio->ep_fb == ep_addr) {
       // Schedule a transmit with the new value if EP is not busy
       // Schedule next transmission - value is changed bytud_audio_n_fb_set() in the meantime or the old value gets sent
-      audiod_fb_send(audio);
+      audiod_fb_send(audio, true);
       return true;
     }
   #endif
diff --git a/src/class/bth/bth_device.c b/src/class/bth/bth_device.c
index 3f1529cb60..b679d6ab6a 100755
--- a/src/class/bth/bth_device.c
+++ b/src/class/bth/bth_device.c
@@ -67,7 +67,7 @@ static bool bt_tx_data(uint8_t ep, void *data, uint16_t len) {
   // skip if previous transfer not complete
   TU_VERIFY(!usbd_edpt_busy(rhport, ep));
 
-  TU_ASSERT(usbd_edpt_xfer(rhport, ep, data, len));
+  TU_ASSERT(usbd_edpt_xfer(rhport, ep, data, len, false));
 
   return true;
 }
@@ -169,7 +169,7 @@ uint16_t btd_open(uint8_t rhport, tusb_desc_interface_t const *itf_desc, uint16_
   itf_desc = (tusb_desc_interface_t const *) tu_desc_next(tu_desc_next(desc_ep));
 
   // Prepare for incoming data from host
-  TU_ASSERT(usbd_edpt_xfer(rhport, _btd_itf.ep_acl_out, _btd_epbuf.epout_buf, CFG_TUD_BTH_DATA_EPSIZE), 0);
+  TU_ASSERT(usbd_edpt_xfer(rhport, _btd_itf.ep_acl_out, _btd_epbuf.epout_buf, CFG_TUD_BTH_DATA_EPSIZE, false), 0);
 
   drv_len = hci_itf_size;
 
@@ -272,7 +272,7 @@ bool btd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result,
     tud_bt_acl_data_received_cb(_btd_epbuf.epout_buf, xferred_bytes);
 
     // prepare for next data
-    TU_ASSERT(usbd_edpt_xfer(rhport, _btd_itf.ep_acl_out, _btd_epbuf.epout_buf, CFG_TUD_BTH_DATA_EPSIZE));
+    TU_ASSERT(usbd_edpt_xfer(rhport, _btd_itf.ep_acl_out, _btd_epbuf.epout_buf, CFG_TUD_BTH_DATA_EPSIZE, false));
   } else if (ep_addr == _btd_itf.ep_ev) {
     tud_bt_event_sent_cb((uint16_t) xferred_bytes);
   } else if (ep_addr == _btd_itf.ep_acl_in) {
diff --git a/src/class/cdc/cdc_device.c b/src/class/cdc/cdc_device.c
index f1c4a3bbfa..94c82cc77f 100644
--- a/src/class/cdc/cdc_device.c
+++ b/src/class/cdc/cdc_device.c
@@ -111,7 +111,7 @@ static bool _prep_out_transaction(uint8_t itf) {
   available = tu_fifo_remaining(&p_cdc->rx_ff);
 
   if (available >= CFG_TUD_CDC_EP_BUFSIZE) {
-    return usbd_edpt_xfer(rhport, p_cdc->ep_out, p_epbuf->epout, CFG_TUD_CDC_EP_BUFSIZE);
+    return usbd_edpt_xfer(rhport, p_cdc->ep_out, p_epbuf->epout, CFG_TUD_CDC_EP_BUFSIZE, false);
   } else {
     // Release endpoint since we don't make any transfer
     usbd_edpt_release(p_cdc->rhport, p_cdc->ep_out);
@@ -196,7 +196,7 @@ bool tud_cdc_n_notify_uart_state (uint8_t itf, const cdc_notify_uart_state_t *st
   notify_msg->request.wLength = sizeof(cdc_notify_uart_state_t);
   notify_msg->serial_state = *state;
 
-  return usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_notify, (uint8_t *)notify_msg, 8 + sizeof(cdc_notify_uart_state_t));
+  return usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_notify, (uint8_t *)notify_msg, 8 + sizeof(cdc_notify_uart_state_t), false);
 }
 
 bool tud_cdc_n_notify_conn_speed_change(uint8_t itf, const cdc_notify_conn_speed_change_t* conn_speed_change) {
@@ -213,7 +213,7 @@ bool tud_cdc_n_notify_conn_speed_change(uint8_t itf, const cdc_notify_conn_speed
   notify_msg->request.wLength = sizeof(cdc_notify_conn_speed_change_t);
   notify_msg->conn_speed_change = *conn_speed_change;
 
-  return usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_notify, (uint8_t *)notify_msg, 8 + sizeof(cdc_notify_conn_speed_change_t));
+  return usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_notify, (uint8_t *)notify_msg, 8 + sizeof(cdc_notify_conn_speed_change_t), false);
 }
 #endif
 
@@ -280,7 +280,7 @@ uint32_t tud_cdc_n_write_flush(uint8_t itf) {
   const uint16_t count = tu_fifo_read_n(&p_cdc->tx_ff, p_epbuf->epin, CFG_TUD_CDC_EP_BUFSIZE);
 
   if (count) {
-    TU_ASSERT(usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_in, p_epbuf->epin, count), 0);
+    TU_ASSERT(usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_in, p_epbuf->epin, count, false), 0);
     return count;
   } else {
     // Release endpoint since we don't make any transfer
@@ -560,7 +560,7 @@ bool cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_
       // xferred_bytes is multiple of EP Packet size and not zero
       if (!tu_fifo_count(&p_cdc->tx_ff) && xferred_bytes && (0 == (xferred_bytes & (BULK_PACKET_SIZE - 1)))) {
         if (usbd_edpt_claim(rhport, p_cdc->ep_in)) {
-          TU_ASSERT(usbd_edpt_xfer(rhport, p_cdc->ep_in, NULL, 0));
+          TU_ASSERT(usbd_edpt_xfer(rhport, p_cdc->ep_in, NULL, 0, false));
         }
       }
     }
diff --git a/src/class/hid/hid_device.c b/src/class/hid/hid_device.c
index b4f24902b7..6ee4cd9c1a 100644
--- a/src/class/hid/hid_device.c
+++ b/src/class/hid/hid_device.c
@@ -128,7 +128,7 @@ bool tud_hid_n_report(uint8_t instance, uint8_t report_id, void const *report, u
     TU_VERIFY(0 == tu_memcpy_s(p_epbuf->epin, CFG_TUD_HID_EP_BUFSIZE, report, len));
   }
 
-  return usbd_edpt_xfer(rhport, p_hid->ep_in, p_epbuf->epin, len);
+  return usbd_edpt_xfer(rhport, p_hid->ep_in, p_epbuf->epin, len, false);
 }
 
 uint8_t tud_hid_n_interface_protocol(uint8_t instance) {
@@ -263,7 +263,7 @@ uint16_t hidd_open(uint8_t rhport, tusb_desc_interface_t const *desc_itf, uint16
 
   // Prepare for output endpoint
   if (p_hid->ep_out) {
-    TU_ASSERT(usbd_edpt_xfer(rhport, p_hid->ep_out, p_epbuf->epout, CFG_TUD_HID_EP_BUFSIZE), drv_len);
+    TU_ASSERT(usbd_edpt_xfer(rhport, p_hid->ep_out, p_epbuf->epout, CFG_TUD_HID_EP_BUFSIZE, false), drv_len);
   }
 
   return drv_len;
@@ -413,7 +413,7 @@ bool hidd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_
     }
 
     // prepare for new transfer
-    TU_ASSERT(usbd_edpt_xfer(rhport, p_hid->ep_out, p_epbuf->epout, CFG_TUD_HID_EP_BUFSIZE));
+    TU_ASSERT(usbd_edpt_xfer(rhport, p_hid->ep_out, p_epbuf->epout, CFG_TUD_HID_EP_BUFSIZE, false));
   }
 
   return true;
diff --git a/src/class/midi/midi_device.c b/src/class/midi/midi_device.c
index 7dac7c4a54..c4b4925d62 100644
--- a/src/class/midi/midi_device.c
+++ b/src/class/midi/midi_device.c
@@ -99,7 +99,7 @@ static void _prep_out_transaction(uint8_t idx) {
   available = tu_fifo_remaining(&p_midi->rx_ff);
 
   if ( available >= CFG_TUD_MIDI_EP_BUFSIZE )  {
-    usbd_edpt_xfer(rhport, p_midi->ep_out, _midid_epbuf[idx].epout, CFG_TUD_MIDI_EP_BUFSIZE);
+    usbd_edpt_xfer(rhport, p_midi->ep_out, _midid_epbuf[idx].epout, CFG_TUD_MIDI_EP_BUFSIZE, false);
   }else
   {
     // Release endpoint since we don't make any transfer
@@ -228,7 +228,7 @@ static uint32_t write_flush(uint8_t idx) {
   uint16_t count = tu_fifo_read_n(&midi->tx_ff, _midid_epbuf[idx].epin, CFG_TUD_MIDI_EP_BUFSIZE);
 
   if (count) {
-    TU_ASSERT( usbd_edpt_xfer(rhport, midi->ep_in, _midid_epbuf[idx].epin, count), 0 );
+    TU_ASSERT( usbd_edpt_xfer(rhport, midi->ep_in, _midid_epbuf[idx].epin, count, false), 0 );
     return count;
   }else {
     // Release endpoint since we don't make any transfer
@@ -548,7 +548,7 @@ bool midid_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32
       // xferred_bytes is multiple of EP size and not zero
       if (!tu_fifo_count(&p_midi->tx_ff) && xferred_bytes && (0 == (xferred_bytes % CFG_TUD_MIDI_EP_BUFSIZE))) {
         if (usbd_edpt_claim(rhport, p_midi->ep_in)) {
-          usbd_edpt_xfer(rhport, p_midi->ep_in, NULL, 0);
+          usbd_edpt_xfer(rhport, p_midi->ep_in, NULL, 0, false);
         }
       }
     }
diff --git a/src/class/msc/msc_device.c b/src/class/msc/msc_device.c
index b0eafd5dac..b272c80c0b 100644
--- a/src/class/msc/msc_device.c
+++ b/src/class/msc/msc_device.c
@@ -113,13 +113,13 @@ static inline bool send_csw(mscd_interface_t* p_msc) {
   p_msc->csw.data_residue = p_msc->cbw.total_bytes - p_msc->xferred_len;
   p_msc->stage = MSC_STAGE_STATUS_SENT;
   memcpy(_mscd_epbuf.buf, &p_msc->csw, sizeof(msc_csw_t));
-  return usbd_edpt_xfer(rhport, p_msc->ep_in , _mscd_epbuf.buf, sizeof(msc_csw_t));
+  return usbd_edpt_xfer(rhport, p_msc->ep_in , _mscd_epbuf.buf, sizeof(msc_csw_t), false);
 }
 
 static inline bool prepare_cbw(mscd_interface_t* p_msc) {
   uint8_t rhport = p_msc->rhport;
   p_msc->stage = MSC_STAGE_CMD;
-  return usbd_edpt_xfer(rhport, p_msc->ep_out,  _mscd_epbuf.buf, sizeof(msc_cbw_t));
+  return usbd_edpt_xfer(rhport, p_msc->ep_out,  _mscd_epbuf.buf, sizeof(msc_cbw_t), false);
 }
 
 static void fail_scsi_op(mscd_interface_t* p_msc, uint8_t status) {
@@ -531,7 +531,7 @@ bool mscd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t event, uint32_t
           } else {
             // Didn't check for case 9 (Ho > Dn), which requires examining scsi command first
             // but it is OK to just receive data then responded with failed status
-            TU_ASSERT(usbd_edpt_xfer(rhport, p_msc->ep_out, _mscd_epbuf.buf, (uint16_t) p_msc->total_len));
+            TU_ASSERT(usbd_edpt_xfer(rhport, p_msc->ep_out, _mscd_epbuf.buf, (uint16_t) p_msc->total_len, false));
           }
         } else {
           // First process if it is a built-in commands
@@ -563,7 +563,7 @@ bool mscd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t event, uint32_t
             } else {
               // cannot return more than host expect
               p_msc->total_len = tu_min32((uint32_t)resplen, p_cbw->total_bytes);
-              TU_ASSERT(usbd_edpt_xfer(rhport, p_msc->ep_in, _mscd_epbuf.buf, (uint16_t) p_msc->total_len));
+              TU_ASSERT(usbd_edpt_xfer(rhport, p_msc->ep_in, _mscd_epbuf.buf, (uint16_t) p_msc->total_len, false));
             }
           }
         }
@@ -860,7 +860,7 @@ static void proc_read10_cmd(mscd_interface_t* p_msc) {
 static void proc_read_io_data(mscd_interface_t* p_msc, int32_t nbytes) {
   const uint8_t rhport = p_msc->rhport;
   if (nbytes > 0) {
-    TU_ASSERT(usbd_edpt_xfer(rhport, p_msc->ep_in, _mscd_epbuf.buf, (uint16_t) nbytes),);
+    TU_ASSERT(usbd_edpt_xfer(rhport, p_msc->ep_in, _mscd_epbuf.buf, (uint16_t) nbytes, false),);
   } else {
     // nbytes is status
     switch (nbytes) {
@@ -896,7 +896,7 @@ static void proc_write10_cmd(mscd_interface_t* p_msc) {
   // remaining bytes capped at class buffer
   uint16_t nbytes = (uint16_t)tu_min32(CFG_TUD_MSC_EP_BUFSIZE, p_cbw->total_bytes - p_msc->xferred_len);
   // Write10 callback will be called later when usb transfer complete
-  TU_ASSERT(usbd_edpt_xfer(p_msc->rhport, p_msc->ep_out, _mscd_epbuf.buf, nbytes),);
+  TU_ASSERT(usbd_edpt_xfer(p_msc->rhport, p_msc->ep_out, _mscd_epbuf.buf, nbytes, false),);
 }
 
 // process new data arrived from WRITE10
diff --git a/src/class/mtp/mtp_device.c b/src/class/mtp/mtp_device.c
index 04bde94153..764019e426 100644
--- a/src/class/mtp/mtp_device.c
+++ b/src/class/mtp/mtp_device.c
@@ -191,7 +191,7 @@ TU_ATTR_UNUSED static const char* _mtp_phase_str[] = {
 //--------------------------------------------------------------------+
 static bool prepare_new_command(mtpd_interface_t* p_mtp) {
   p_mtp->phase = MTP_PHASE_COMMAND;
-  return usbd_edpt_xfer(p_mtp->rhport, p_mtp->ep_out, _mtpd_epbuf.buf, CFG_TUD_MTP_EP_BUFSIZE);
+  return usbd_edpt_xfer(p_mtp->rhport, p_mtp->ep_out, _mtpd_epbuf.buf, CFG_TUD_MTP_EP_BUFSIZE, false);
 }
 
 static bool mtpd_data_xfer(mtp_container_info_t* p_container, uint8_t ep_addr) {
@@ -219,7 +219,7 @@ static bool mtpd_data_xfer(mtp_container_info_t* p_container, uint8_t ep_addr) {
   if (xact_len) {
     // already transferred all bytes in header's length. Application make an unnecessary extra call
     TU_VERIFY(usbd_edpt_claim(p_mtp->rhport, ep_addr));
-    TU_ASSERT(usbd_edpt_xfer(p_mtp->rhport, ep_addr, _mtpd_epbuf.buf, xact_len));
+    TU_ASSERT(usbd_edpt_xfer(p_mtp->rhport, ep_addr, _mtpd_epbuf.buf, xact_len, false));
   }
   return true;
 }
@@ -238,7 +238,7 @@ bool tud_mtp_response_send(mtp_container_info_t* p_container) {
   p_container->header->type = MTP_CONTAINER_TYPE_RESPONSE_BLOCK;
   p_container->header->transaction_id = p_mtp->command.header.transaction_id;
   TU_VERIFY(usbd_edpt_claim(p_mtp->rhport, p_mtp->ep_in));
-  return usbd_edpt_xfer(p_mtp->rhport, p_mtp->ep_in, _mtpd_epbuf.buf, (uint16_t)p_container->header->len);
+  return usbd_edpt_xfer(p_mtp->rhport, p_mtp->ep_in, _mtpd_epbuf.buf, (uint16_t) p_container->header->len, false);
 }
 
 bool tud_mtp_mounted(void) {
@@ -251,7 +251,7 @@ bool tud_mtp_event_send(mtp_event_t* event) {
   TU_VERIFY(p_mtp->ep_event != 0);
   _mtpd_epbuf.buf_event = *event;
   TU_VERIFY(usbd_edpt_claim(p_mtp->rhport, p_mtp->ep_event)); // Claim the endpoint
-  return usbd_edpt_xfer(p_mtp->rhport, p_mtp->ep_event, (uint8_t*) &_mtpd_epbuf.buf_event, sizeof(mtp_event_t));
+  return usbd_edpt_xfer(p_mtp->rhport, p_mtp->ep_event, (uint8_t*) &_mtpd_epbuf.buf_event, sizeof(mtp_event_t), false);
 }
 
 //--------------------------------------------------------------------+
diff --git a/src/class/net/ecm_rndis_device.c b/src/class/net/ecm_rndis_device.c
index 7dff668233..eaa82c187e 100644
--- a/src/class/net/ecm_rndis_device.c
+++ b/src/class/net/ecm_rndis_device.c
@@ -82,12 +82,12 @@ static bool can_xmit;
 static bool ecm_link_is_up = true;  // Store link state for ECM mode
 
 void tud_network_recv_renew(void) {
-  usbd_edpt_xfer(0, _netd_itf.ep_out, _netd_epbuf.rx, NETD_PACKET_SIZE);
+  usbd_edpt_xfer(0, _netd_itf.ep_out, _netd_epbuf.rx, NETD_PACKET_SIZE, false);
 }
 
 static void do_in_xfer(uint8_t *buf, uint16_t len) {
   can_xmit = false;
-  usbd_edpt_xfer(0, _netd_itf.ep_in, buf, len);
+  usbd_edpt_xfer(0, _netd_itf.ep_in, buf, len, false);
 }
 
 void netd_report(uint8_t *buf, uint16_t len) {
@@ -100,7 +100,7 @@ void netd_report(uint8_t *buf, uint16_t len) {
   }
 
   memcpy(_netd_epbuf.notify, buf, len);
-  usbd_edpt_xfer(rhport, _netd_itf.ep_notif, _netd_epbuf.notify, len);
+  usbd_edpt_xfer(rhport, _netd_itf.ep_notif, _netd_epbuf.notify, len, false);
 }
 
 //--------------------------------------------------------------------+
diff --git a/src/class/net/ncm_device.c b/src/class/net/ncm_device.c
index 02833c5f17..335f6ad09d 100644
--- a/src/class/net/ncm_device.c
+++ b/src/class/net/ncm_device.c
@@ -205,7 +205,7 @@ static void notification_xmit(uint8_t rhport, bool force_next) {
 
     uint16_t notif_len = sizeof(notify_speed_change.header) + notify_speed_change.header.wLength;
     ncm_epbuf.epnotif = notify_speed_change;
-    usbd_edpt_xfer(rhport, ncm_interface.ep_notif, (uint8_t*) &ncm_epbuf.epnotif, notif_len);
+    usbd_edpt_xfer(rhport, ncm_interface.ep_notif, (uint8_t*) &ncm_epbuf.epnotif, notif_len, false);
 
     ncm_interface.notification_xmit_state = NOTIFICATION_CONNECTED;
     ncm_interface.notification_xmit_is_running = true;
@@ -227,7 +227,7 @@ static void notification_xmit(uint8_t rhport, bool force_next) {
 
     uint16_t notif_len = sizeof(notify_connected.header) + notify_connected.header.wLength;
     ncm_epbuf.epnotif = notify_connected;
-    usbd_edpt_xfer(rhport, ncm_interface.ep_notif, (uint8_t *) &ncm_epbuf.epnotif, notif_len);
+    usbd_edpt_xfer(rhport, ncm_interface.ep_notif, (uint8_t *) &ncm_epbuf.epnotif, notif_len, false);
 
     ncm_interface.notification_xmit_state = NOTIFICATION_DONE;
     ncm_interface.notification_xmit_is_running = true;
@@ -331,7 +331,7 @@ static bool xmit_insert_required_zlp(uint8_t rhport, uint32_t xferred_bytes) {
   TU_LOG_DRV("xmit_insert_required_zlp! (%u)\n", (unsigned) xferred_bytes);
 
   // start transmission of the ZLP
-  usbd_edpt_xfer(rhport, ncm_interface.ep_in, NULL, 0);
+  usbd_edpt_xfer(rhport, ncm_interface.ep_in, NULL, 0, false);
 
   return true;
 } // xmit_insert_required_zlp
@@ -377,7 +377,7 @@ static void xmit_start_if_possible(uint8_t rhport) {
   }
 
   // Kick off an endpoint transfer
-  usbd_edpt_xfer(0, ncm_interface.ep_in, ncm_interface.xmit_tinyusb_ntb->data, ncm_interface.xmit_tinyusb_ntb->nth.wBlockLength);
+  usbd_edpt_xfer(0, ncm_interface.ep_in, ncm_interface.xmit_tinyusb_ntb->data, ncm_interface.xmit_tinyusb_ntb->nth.wBlockLength, false);
 } // xmit_start_if_possible
 
 /**
@@ -526,7 +526,7 @@ static void recv_try_to_start_new_reception(uint8_t rhport) {
 
   // initiate transfer
   TU_LOG_DRV("  start reception\n");
-  bool r = usbd_edpt_xfer(rhport, ncm_interface.ep_out, ncm_interface.recv_tinyusb_ntb->data, CFG_TUD_NCM_OUT_NTB_MAX_SIZE);
+  bool r = usbd_edpt_xfer(rhport, ncm_interface.ep_out, ncm_interface.recv_tinyusb_ntb->data, CFG_TUD_NCM_OUT_NTB_MAX_SIZE, false);
   if (!r) {
     recv_put_ntb_into_free_list(ncm_interface.recv_tinyusb_ntb);
     ncm_interface.recv_tinyusb_ntb = NULL;
diff --git a/src/class/usbtmc/usbtmc_device.c b/src/class/usbtmc/usbtmc_device.c
index 3f6bedd4c7..4b0bb01ecd 100644
--- a/src/class/usbtmc/usbtmc_device.c
+++ b/src/class/usbtmc/usbtmc_device.c
@@ -261,7 +261,7 @@ bool tud_usbtmc_transmit_dev_msg_data(
   bool stateChanged =
       atomicChangeState(STATE_TX_REQUESTED, (packetLen >= txBufLen) ? STATE_TX_INITIATED : STATE_TX_SHORTED);
   TU_VERIFY(stateChanged);
-  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) packetLen));
+  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) packetLen, false));
   return true;
 }
 
@@ -273,7 +273,7 @@ bool tud_usbtmc_transmit_notification_data(const void *data, size_t len) {
   TU_VERIFY(usbd_edpt_busy(usbtmc_state.rhport, usbtmc_state.ep_int_in));
 
   TU_VERIFY(tu_memcpy_s(usbtmc_epbuf.epnotif, CFG_TUD_USBTMC_INT_EP_SIZE, data, len) == 0);
-  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_int_in, usbtmc_epbuf.epnotif, (uint16_t) len));
+  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_int_in, usbtmc_epbuf.epnotif, (uint16_t) len, false));
   return true;
 }
 
@@ -396,7 +396,7 @@ bool tud_usbtmc_start_bus_read(void) {
     default:
       return false;
   }
-  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_bulk_out, usbtmc_epbuf.epout, (uint16_t) usbtmc_state.ep_bulk_out_wMaxPacketSize));
+  TU_VERIFY(usbd_edpt_xfer(usbtmc_state.rhport, usbtmc_state.ep_bulk_out, usbtmc_epbuf.epout, (uint16_t) usbtmc_state.ep_bulk_out_wMaxPacketSize, false));
   return true;
 }
 
@@ -567,7 +567,7 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
         if (usbtmc_state.transfer_size_remaining >= USBTMCD_BUFFER_SIZE) {
           // Copy buffer to ensure alignment correctness
           memcpy(usbtmc_epbuf.epin, usbtmc_state.devInBuffer, USBTMCD_BUFFER_SIZE);
-          TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, USBTMCD_BUFFER_SIZE));
+          TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, USBTMCD_BUFFER_SIZE, false));
           usbtmc_state.devInBuffer += USBTMCD_BUFFER_SIZE;
           usbtmc_state.transfer_size_remaining -= USBTMCD_BUFFER_SIZE;
           usbtmc_state.transfer_size_sent += USBTMCD_BUFFER_SIZE;
@@ -578,7 +578,7 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
           usbtmc_state.transfer_size_sent += packetLen;
           usbtmc_state.transfer_size_remaining = 0;
           usbtmc_state.devInBuffer = NULL;
-          TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) packetLen));
+          TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) packetLen, false));
           if (((packetLen % usbtmc_state.ep_bulk_in_wMaxPacketSize) != 0) || (packetLen == 0)) {
             usbtmc_state.state = STATE_TX_SHORTED;
           }
@@ -587,7 +587,7 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
 
       case STATE_ABORTING_BULK_IN:
         // need to send short packet  (ZLP?)
-        TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) 0u));
+        TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) 0u, false));
         usbtmc_state.state = STATE_ABORTING_BULK_IN_SHORTED;
         return true;
 
@@ -713,7 +713,7 @@ bool usbtmcd_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_request
         criticalLeave();
         if (usbtmc_state.transfer_size_sent == 0) {
           // Send short packet, nothing is in the buffer yet
-          TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) 0u));
+          TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_epbuf.epin, (uint16_t) 0u, false));
           usbtmc_state.state = STATE_ABORTING_BULK_IN_SHORTED;
         }
         TU_VERIFY(tud_usbtmc_initiate_abort_bulk_in_cb(&(rsp.USBTMC_status)));
@@ -841,7 +841,7 @@ bool usbtmcd_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_request
                   },
                   .StatusByte = tud_usbtmc_get_stb_cb(&(rsp.USBTMC_status))};
           // Must be queued before control request response sent (USB488v1.0 4.3.1.2)
-          usbd_edpt_xfer(rhport, usbtmc_state.ep_int_in, (void *) &intMsg, sizeof(intMsg));
+          usbd_edpt_xfer(rhport, usbtmc_state.ep_int_in, (void *) &intMsg, sizeof(intMsg), false);
         }
       } else {
         rsp.statusByte = tud_usbtmc_get_stb_cb(&(rsp.USBTMC_status));
diff --git a/src/class/video/video_device.c b/src/class/video/video_device.c
index 5c00cc358a..2c610c469e 100644
--- a/src/class/video/video_device.c
+++ b/src/class/video/video_device.c
@@ -1262,7 +1262,7 @@ bool tud_video_n_frame_xfer(uint_fast8_t ctl_idx, uint_fast8_t stm_idx, void *bu
   stm->buffer     = (uint8_t*)buffer;
   stm->bufsize    = bufsize;
   uint_fast16_t pkt_len = _prepare_in_payload(stm, stm_epbuf->buf);
-  TU_ASSERT( usbd_edpt_xfer(0, ep_addr, stm_epbuf->buf, (uint16_t) pkt_len), 0);
+  TU_ASSERT( usbd_edpt_xfer(0, ep_addr, stm_epbuf->buf, (uint16_t) pkt_len, false), 0);
   return true;
 }
 
@@ -1433,7 +1433,7 @@ bool videod_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint3
     /* Claim the endpoint */
     TU_VERIFY( usbd_edpt_claim(rhport, ep_addr), 0);
     uint_fast16_t pkt_len = _prepare_in_payload(stm, stm_epbuf->buf);
-    TU_ASSERT( usbd_edpt_xfer(rhport, ep_addr, stm_epbuf->buf, (uint16_t) pkt_len), 0);
+    TU_ASSERT( usbd_edpt_xfer(rhport, ep_addr, stm_epbuf->buf, (uint16_t) pkt_len, false), 0);
   } else {
     stm->buffer  = NULL;
     stm->bufsize = 0;
diff --git a/src/device/dcd.h b/src/device/dcd.h
index 400f62bff5..f901562354 100644
--- a/src/device/dcd.h
+++ b/src/device/dcd.h
@@ -158,11 +158,11 @@ bool dcd_edpt_open            (uint8_t rhport, tusb_desc_endpoint_t const * desc
 void dcd_edpt_close_all       (uint8_t rhport);
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer            (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes);
+bool dcd_edpt_xfer            (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr);
 
 // Submit an transfer using fifo, When complete dcd_event_xfer_complete() is invoked to notify the stack
 // This API is optional, may be useful for register-based for transferring data.
-bool dcd_edpt_xfer_fifo       (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes);
+bool dcd_edpt_xfer_fifo       (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr);
 
 // Stall endpoint, any queuing transfer should be removed from endpoint
 void dcd_edpt_stall           (uint8_t rhport, uint8_t ep_addr);
diff --git a/src/device/usbd.c b/src/device/usbd.c
index 339ccf4b4f..a664c2186b 100644
--- a/src/device/usbd.c
+++ b/src/device/usbd.c
@@ -415,8 +415,8 @@ TU_ATTR_WEAK usbd_class_driver_t const* usbd_app_driver_get_cb(uint8_t* driver_c
   return NULL;
 }
 
-TU_ATTR_WEAK bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes) {
-  (void) rhport; (void) ep_addr; (void) ff; (void) total_bytes;
+TU_ATTR_WEAK bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr) {
+  (void) rhport; (void) ep_addr; (void) ff; (void) total_bytes; (void) is_isr;
   return false;
 }
 
@@ -1410,7 +1410,7 @@ bool usbd_edpt_release(uint8_t rhport, uint8_t ep_addr) {
   return tu_edpt_release(ep_state, _usbd_mutex);
 }
 
-bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes, bool is_isr) {
   rhport = _usbd_rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
@@ -1433,7 +1433,7 @@ bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t t
   // could return and USBD task can preempt and clear the busy
   _usbd_dev.ep_status[epnum][dir].busy = 1;
 
-  if (dcd_edpt_xfer(rhport, ep_addr, buffer, total_bytes)) {
+  if (dcd_edpt_xfer(rhport, ep_addr, buffer, total_bytes, is_isr)) {
     return true;
   } else {
     // DCD error, mark endpoint as ready to allow next transfer
@@ -1449,7 +1449,7 @@ bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t t
 // bytes should be written and second to keep the return value free to give back a boolean
 // success message. If total_bytes is too big, the FIFO will copy only what is available
 // into the USB buffer!
-bool usbd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_t total_bytes) {
+bool usbd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_t total_bytes, bool is_isr) {
   rhport = _usbd_rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
@@ -1464,7 +1464,7 @@ bool usbd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_
   // and usbd task can preempt and clear the busy
   _usbd_dev.ep_status[epnum][dir].busy = 1;
 
-  if (dcd_edpt_xfer_fifo(rhport, ep_addr, ff, total_bytes)) {
+  if (dcd_edpt_xfer_fifo(rhport, ep_addr, ff, total_bytes, is_isr)) {
     TU_LOG_USBD("OK\r\n");
     return true;
   } else {
diff --git a/src/device/usbd_control.c b/src/device/usbd_control.c
index c9700fd9db..b753624255 100644
--- a/src/device/usbd_control.c
+++ b/src/device/usbd_control.c
@@ -71,7 +71,7 @@ CFG_TUD_MEM_SECTION static struct {
 static inline bool status_stage_xact(uint8_t rhport, const tusb_control_request_t* request) {
   // Opposite to endpoint in Data Phase
   const uint8_t ep_addr = request->bmRequestType_bit.direction ? EDPT_CTRL_OUT : EDPT_CTRL_IN;
-  return usbd_edpt_xfer(rhport, ep_addr, NULL, 0);
+  return usbd_edpt_xfer(rhport, ep_addr, NULL, 0, false);
 }
 
 // Status phase
@@ -98,7 +98,7 @@ static bool data_stage_xact(uint8_t rhport) {
     }
   }
 
-  return usbd_edpt_xfer(rhport, ep_addr, xact_len ? _ctrl_epbuf.buf : NULL, xact_len);
+  return usbd_edpt_xfer(rhport, ep_addr, xact_len ? _ctrl_epbuf.buf : NULL, xact_len, false);
 }
 
 // Transmit data to/from the control endpoint.
diff --git a/src/device/usbd_pvt.h b/src/device/usbd_pvt.h
index a688cf4979..a1c884f126 100644
--- a/src/device/usbd_pvt.h
+++ b/src/device/usbd_pvt.h
@@ -84,10 +84,10 @@ bool usbd_edpt_open(uint8_t rhport, tusb_desc_endpoint_t const * desc_ep);
 void usbd_edpt_close(uint8_t rhport, uint8_t ep_addr);
 
 // Submit a usb transfer
-bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes);
+bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr);
 
 // Submit a usb ISO transfer by use of a FIFO (ring buffer) - all bytes in FIFO get transmitted
-bool usbd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes);
+bool usbd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr);
 
 // Claim an endpoint before submitting a transfer.
 // If caller does not make any transfer, it must release endpoint for others.
diff --git a/src/portable/bridgetek/ft9xx/dcd_ft9xx.c b/src/portable/bridgetek/ft9xx/dcd_ft9xx.c
index 34a8be3b66..76a54e62e2 100644
--- a/src/portable/bridgetek/ft9xx/dcd_ft9xx.c
+++ b/src/portable/bridgetek/ft9xx/dcd_ft9xx.c
@@ -556,7 +556,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
   (void)dev_addr;
 
   // Respond with status. There is no checking that the address is in range.
-  dcd_edpt_xfer(rhport, tu_edpt_addr(USBD_EP_0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(USBD_EP_0, TUSB_DIR_IN), NULL, 0, false);
 
   // Set the update bit for the address register.
   dev_addr |= 0x80;
@@ -807,8 +807,9 @@ void dcd_edpt_close_all(uint8_t rhport)
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   uint8_t ep_number = tu_edpt_number(ep_addr);
   uint8_t ep_dir = tu_edpt_dir(ep_addr);
@@ -891,8 +892,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 }
 
 // Submit a transfer where is managed by FIFO, When complete dcd_event_xfer_complete() is invoked to notify the stack - optional, however, must be listed in usbd.c
-bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t *ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   (void)ep_addr;
   (void)ff;
diff --git a/src/portable/chipidea/ci_fs/dcd_ci_fs.c b/src/portable/chipidea/ci_fs/dcd_ci_fs.c
index 11ddb683f3..558d64b575 100644
--- a/src/portable/chipidea/ci_fs/dcd_ci_fs.c
+++ b/src/portable/chipidea/ci_fs/dcd_ci_fs.c
@@ -131,7 +131,7 @@ static void prepare_next_setup_packet(uint8_t rhport)
   _dcd.bdt[0][1][in_odd].data      = 1;
   _dcd.bdt[0][1][in_odd ^ 1].data  = 0;
   dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_OUT),
-                _dcd.setup_packet, sizeof(_dcd.setup_packet));
+                _dcd.setup_packet, sizeof(_dcd.setup_packet), false);
 }
 
 static void process_stall(uint8_t rhport)
@@ -303,7 +303,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
 {
   _dcd.addr = dev_addr & 0x7F;
   /* Response with status first before changing device address */
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport)
@@ -419,8 +419,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   dcd_int_enable(rhport);
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   const unsigned epn      = tu_edpt_number(ep_addr);
   const unsigned dir      = tu_edpt_dir(ep_addr);
   endpoint_state_t    *ep = &_dcd.endpoint[epn][dir];
diff --git a/src/portable/chipidea/ci_hs/dcd_ci_hs.c b/src/portable/chipidea/ci_hs/dcd_ci_hs.c
index 244f5a2d40..808c293a53 100644
--- a/src/portable/chipidea/ci_hs/dcd_ci_hs.c
+++ b/src/portable/chipidea/ci_hs/dcd_ci_hs.c
@@ -277,7 +277,7 @@ void dcd_int_disable(uint8_t rhport)
 void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
 {
   // Response with status first before changing device address
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 
   ci_hs_regs_t* dcd_reg = CI_HS_REG(rhport);
   dcd_reg->DEVICEADDR = (dev_addr << 25) | TU_BIT(24);
@@ -465,8 +465,9 @@ static void qhd_start_xfer(uint8_t rhport, uint8_t epnum, uint8_t dir)
   dcd_reg->ENDPTPRIME = TU_BIT(epnum + (dir ? 16 : 0));
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir   = tu_edpt_dir(ep_addr);
 
@@ -486,8 +487,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t t
 #if !CFG_TUD_MEM_DCACHE_ENABLE
 // fifo has to be aligned to 4k boundary
 // It's incompatible with dcache enabled transfer, since neither address nor size is aligned to cache line
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir   = tu_edpt_dir(ep_addr);
 
diff --git a/src/portable/dialog/da146xx/dcd_da146xx.c b/src/portable/dialog/da146xx/dcd_da146xx.c
index 56ecb7575b..5beb62b4d4 100644
--- a/src/portable/dialog/da146xx/dcd_da146xx.c
+++ b/src/portable/dialog/da146xx/dcd_da146xx.c
@@ -837,7 +837,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
   // Set default address for one ZLP
   USB->USB_EPC0_REG = USB_USB_EPC0_REG_USB_DEF_Msk;
   USB->USB_FAR_REG = (dev_addr & USB_USB_FAR_REG_USB_AD_Msk) | USB_USB_FAR_REG_USB_AD_EN_Msk;
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport)
@@ -1025,8 +1025,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   tu_memclr(xfer, sizeof(*xfer));
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir   = tu_edpt_dir(ep_addr);
   xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, dir);
diff --git a/src/portable/mentor/musb/dcd_musb.c b/src/portable/mentor/musb/dcd_musb.c
index 4fce08dd9a..1e4ec00159 100644
--- a/src/portable/mentor/musb/dcd_musb.c
+++ b/src/portable/mentor/musb/dcd_musb.c
@@ -772,8 +772,9 @@ void dcd_edpt_close_all(uint8_t rhport)
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   bool ret;
   // TU_LOG1("X %x %d\r\n", ep_addr, total_bytes);
@@ -794,8 +795,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t t
 
 // Submit a transfer where is managed by FIFO, When complete dcd_event_xfer_complete() is invoked to notify the stack
 // - optional, however, must be listed in usbd.c
-bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   bool ret;
   // TU_LOG1("X %x %d\r\n", ep_addr, total_bytes);
diff --git a/src/portable/microchip/pic/dcd_pic.c b/src/portable/microchip/pic/dcd_pic.c
index b4a6981992..3114295de6 100644
--- a/src/portable/microchip/pic/dcd_pic.c
+++ b/src/portable/microchip/pic/dcd_pic.c
@@ -545,7 +545,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
 {
   _dcd.addr = dev_addr & 0x7F;
   /* Response with status first before changing device address */
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport)
@@ -687,8 +687,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   if (ie) intr_enable(rhport);
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
 
   const unsigned epn      = tu_edpt_number(ep_addr);
   const unsigned dir      = tu_edpt_dir(ep_addr);
diff --git a/src/portable/microchip/pic32mz/dcd_pic32mz.c b/src/portable/microchip/pic32mz/dcd_pic32mz.c
index cbd157d6bc..a903c3ae20 100644
--- a/src/portable/microchip/pic32mz/dcd_pic32mz.c
+++ b/src/portable/microchip/pic32mz/dcd_pic32mz.c
@@ -444,8 +444,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   (void) ep_addr;
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir   = tu_edpt_dir(ep_addr);
   xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, dir);
diff --git a/src/portable/microchip/samd/dcd_samd.c b/src/portable/microchip/samd/dcd_samd.c
index e43439f2af..8293273e5e 100644
--- a/src/portable/microchip/samd/dcd_samd.c
+++ b/src/portable/microchip/samd/dcd_samd.c
@@ -142,7 +142,7 @@ void dcd_set_address (uint8_t rhport, uint8_t dev_addr)
   (void) dev_addr;
 
   // Response with zlp status
-  dcd_edpt_xfer(rhport, 0x80, NULL, 0);
+  dcd_edpt_xfer(rhport, 0x80, NULL, 0, false);
 
   // DCD can only set address after status for this request is complete
   // do it at dcd_edpt0_status_complete()
@@ -258,8 +258,9 @@ void dcd_edpt_close_all (uint8_t rhport)
   // TODO implement dcd_edpt_close_all()
 }
 
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
diff --git a/src/portable/microchip/samg/dcd_samg.c b/src/portable/microchip/samg/dcd_samg.c
index a5c768839e..c6c7f15d15 100644
--- a/src/portable/microchip/samg/dcd_samg.c
+++ b/src/portable/microchip/samg/dcd_samg.c
@@ -175,7 +175,7 @@ void dcd_set_address (uint8_t rhport, uint8_t dev_addr)
   (void) dev_addr;
 
   // Response with zlp status
-  dcd_edpt_xfer(rhport, 0x80, NULL, 0);
+  dcd_edpt_xfer(rhport, 0x80, NULL, 0, false);
 
   // DCD can only set address after status for this request is complete.
   // do it at dcd_edpt0_status_complete()
@@ -282,8 +282,9 @@ void dcd_edpt_close_all (uint8_t rhport)
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
@@ -309,8 +310,9 @@ bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t
 }
 
 #if 0 // TODO support dcd_edpt_xfer_fifo API
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
   return true;
 }
diff --git a/src/portable/microchip/samx7x/dcd_samx7x.c b/src/portable/microchip/samx7x/dcd_samx7x.c
index 8aec1568d0..57c0fcb4de 100644
--- a/src/portable/microchip/samx7x/dcd_samx7x.c
+++ b/src/portable/microchip/samx7x/dcd_samx7x.c
@@ -132,7 +132,7 @@ void dcd_set_address (uint8_t rhport, uint8_t dev_addr)
   // do it at dcd_edpt0_status_complete()
 
   // Response with zlp status
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 // Wake up host
@@ -605,8 +605,9 @@ static void dcd_transmit_packet(xfer_ctl_t * xfer, uint8_t ep_ix)
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir   = tu_edpt_dir(ep_addr);
@@ -666,8 +667,9 @@ bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t
 // bytes should be written and second to keep the return value free to give back a boolean
 // success message. If total_bytes is too big, the FIFO will copy only what is available
 // into the USB buffer!
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir   = tu_edpt_dir(ep_addr);
diff --git a/src/portable/mindmotion/mm32/dcd_mm32f327x_otg.c b/src/portable/mindmotion/mm32/dcd_mm32f327x_otg.c
index 1ce3da27ee..929cb40c4c 100644
--- a/src/portable/mindmotion/mm32/dcd_mm32f327x_otg.c
+++ b/src/portable/mindmotion/mm32/dcd_mm32f327x_otg.c
@@ -127,7 +127,7 @@ static void prepare_next_setup_packet(uint8_t rhport)
   _dcd.bdt[0][1][in_odd].data      = 1;
   _dcd.bdt[0][1][in_odd ^ 1].data  = 0;
   dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_OUT),
-                _dcd.setup_packet, sizeof(_dcd.setup_packet));
+                _dcd.setup_packet, sizeof(_dcd.setup_packet), false);
 }
 
 static void process_stall(uint8_t rhport)
@@ -282,7 +282,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
   (void) rhport;
   _dcd.addr = dev_addr & 0x7F;
   /* Response with status first before changing device address */
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 #ifdef __GNUC__ // caused by extra declaration of SystemCoreClock in freeRTOSConfig.h
@@ -381,8 +381,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   bd->head            = 0;
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
   NVIC_DisableIRQ(USB_FS_IRQn);
   const unsigned epn = ep_addr & 0xFu;
diff --git a/src/portable/nordic/nrf5x/dcd_nrf5x.c b/src/portable/nordic/nrf5x/dcd_nrf5x.c
index 9e5f5117ff..89dff49955 100644
--- a/src/portable/nordic/nrf5x/dcd_nrf5x.c
+++ b/src/portable/nordic/nrf5x/dcd_nrf5x.c
@@ -426,7 +426,8 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr) {
   __DSB();
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   (void) rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
diff --git a/src/portable/nuvoton/nuc120/dcd_nuc120.c b/src/portable/nuvoton/nuc120/dcd_nuc120.c
index 0edebf1590..d9a0e3fa88 100644
--- a/src/portable/nuvoton/nuc120/dcd_nuc120.c
+++ b/src/portable/nuvoton/nuc120/dcd_nuc120.c
@@ -294,8 +294,9 @@ void dcd_edpt_close_all (uint8_t rhport)
   // TODO implement dcd_edpt_close_all()
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   /* mine the data for the information we need */
@@ -326,8 +327,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 }
 
 #if 0 // TODO support dcd_edpt_xfer_fifo API
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   /* mine the data for the information we need */
diff --git a/src/portable/nuvoton/nuc121/dcd_nuc121.c b/src/portable/nuvoton/nuc121/dcd_nuc121.c
index 37210ea34e..a4dfe24faf 100644
--- a/src/portable/nuvoton/nuc121/dcd_nuc121.c
+++ b/src/portable/nuvoton/nuc121/dcd_nuc121.c
@@ -323,8 +323,9 @@ void dcd_edpt_close_all (uint8_t rhport)
   // TODO implement dcd_edpt_close_all()
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   /* mine the data for the information we need */
@@ -355,8 +356,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 }
 
 #if 0 // TODO support dcd_edpt_xfer_fifo API
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   /* mine the data for the information we need */
diff --git a/src/portable/nuvoton/nuc505/dcd_nuc505.c b/src/portable/nuvoton/nuc505/dcd_nuc505.c
index fa457d8612..25e3f22031 100644
--- a/src/portable/nuvoton/nuc505/dcd_nuc505.c
+++ b/src/portable/nuvoton/nuc505/dcd_nuc505.c
@@ -376,8 +376,9 @@ void dcd_edpt_close_all (uint8_t rhport)
   // TODO implement dcd_edpt_close_all()
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   if (0x80 == ep_addr) /* control EP0 IN */
@@ -437,8 +438,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 }
 
 #if 0 // TODO support dcd_edpt_xfer_fifo API
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   TU_ASSERT(0x80 != ep_addr && 0x00 != ep_addr);  // Must not be used for control stuff
diff --git a/src/portable/nxp/khci/dcd_khci.c b/src/portable/nxp/khci/dcd_khci.c
index 3d5e195a97..8941ca7662 100644
--- a/src/portable/nxp/khci/dcd_khci.c
+++ b/src/portable/nxp/khci/dcd_khci.c
@@ -129,7 +129,7 @@ static void prepare_next_setup_packet(uint8_t rhport)
   _dcd.bdt[0][1][in_odd].data      = 1;
   _dcd.bdt[0][1][in_odd ^ 1].data  = 0;
   dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_OUT),
-                _dcd.setup_packet, sizeof(_dcd.setup_packet));
+                _dcd.setup_packet, sizeof(_dcd.setup_packet), false);
 }
 
 static void process_stall(uint8_t rhport)
@@ -314,7 +314,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
 {
   _dcd.addr = dev_addr & 0x7F;
   /* Response with status first before changing device address */
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport)
@@ -428,8 +428,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   if (ie) NVIC_EnableIRQ(USB0_IRQn);
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
   const unsigned epn      = tu_edpt_number(ep_addr);
   const unsigned dir      = tu_edpt_dir(ep_addr);
diff --git a/src/portable/nxp/lpc17_40/dcd_lpc17_40.c b/src/portable/nxp/lpc17_40/dcd_lpc17_40.c
index 855c59cd1c..364cf8de49 100644
--- a/src/portable/nxp/lpc17_40/dcd_lpc17_40.c
+++ b/src/portable/nxp/lpc17_40/dcd_lpc17_40.c
@@ -205,7 +205,7 @@ void dcd_int_disable(uint8_t rhport)
 void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
 {
   // Response with status first before changing device address
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 
   sie_write(SIE_CMDCODE_SET_ADDRESS, 1, 0x80 | dev_addr); // 7th bit is : device_enable
 
@@ -399,8 +399,9 @@ static bool control_xact(uint8_t rhport, uint8_t dir, uint8_t * buffer, uint8_t
   return true;
 }
 
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   // Control transfer is not DMA support, and must be done in slave mode
   if ( tu_edpt_number(ep_addr) == 0 )
   {
diff --git a/src/portable/nxp/lpc_ip3511/dcd_lpc_ip3511.c b/src/portable/nxp/lpc_ip3511/dcd_lpc_ip3511.c
index 7c637ce0c9..143b0277c4 100644
--- a/src/portable/nxp/lpc_ip3511/dcd_lpc_ip3511.c
+++ b/src/portable/nxp/lpc_ip3511/dcd_lpc_ip3511.c
@@ -322,7 +322,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
   dcd_registers_t* dcd_reg = _dcd_controller[rhport].regs;
 
   // Response with status first before changing device address
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 
   dcd_reg->DEVCMDSTAT &= ~DEVCMDSTAT_DEVICE_ADDR_MASK;
   dcd_reg->DEVCMDSTAT |= dev_addr;
@@ -464,7 +464,8 @@ static void prepare_ep_xfer(uint8_t rhport, uint8_t ep_id, uint16_t buf_offset,
   ep_cs[0].cmd_sts.active = 1;
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   uint8_t const ep_id = ep_addr2id(ep_addr);
 
   if (!buffer || total_bytes == 0) {
diff --git a/src/portable/raspberrypi/pio_usb/dcd_pio_usb.c b/src/portable/raspberrypi/pio_usb/dcd_pio_usb.c
index 60afbd4352..5e3dd7fafd 100644
--- a/src/portable/raspberrypi/pio_usb/dcd_pio_usb.c
+++ b/src/portable/raspberrypi/pio_usb/dcd_pio_usb.c
@@ -76,7 +76,7 @@ void dcd_set_address (uint8_t rhport, uint8_t dev_addr)
 {
   // must be called before queuing status
   pio_usb_device_set_address(dev_addr);
-  dcd_edpt_xfer(rhport, 0x80, NULL, 0);
+  dcd_edpt_xfer(rhport, 0x80, NULL, 0, false);
 }
 
 // Wake up host
@@ -114,15 +114,16 @@ void dcd_edpt_close_all (uint8_t rhport)
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
   endpoint_t *ep = pio_usb_device_get_endpoint_by_address(ep_addr);
   return pio_usb_ll_transfer_start(ep, buffer, total_bytes);
 }
 
 // Submit a transfer where is managed by FIFO, When complete dcd_event_xfer_complete() is invoked to notify the stack - optional, however, must be listed in usbd.c
-//bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+//bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 //{
 //  (void) rhport;
 //  (void) ep_addr;
diff --git a/src/portable/raspberrypi/rp2040/dcd_rp2040.c b/src/portable/raspberrypi/rp2040/dcd_rp2040.c
index a89c2f42bf..15852f29fd 100644
--- a/src/portable/raspberrypi/rp2040/dcd_rp2040.c
+++ b/src/portable/raspberrypi/rp2040/dcd_rp2040.c
@@ -526,7 +526,8 @@ void dcd_edpt_close_all(uint8_t rhport) {
   reset_non_control_endpoints();
 }
 
-bool dcd_edpt_xfer(__unused uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(__unused uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   assert(rhport == 0);
   hw_endpoint_xfer(ep_addr, buffer, total_bytes);
   return true;
diff --git a/src/portable/renesas/rusb2/dcd_rusb2.c b/src/portable/renesas/rusb2/dcd_rusb2.c
index ecd28973c7..6ac1c5ee40 100644
--- a/src/portable/renesas/rusb2/dcd_rusb2.c
+++ b/src/portable/renesas/rusb2/dcd_rusb2.c
@@ -859,8 +859,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
   _dcd.ep[dir][epn] = 0;
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   rusb2_reg_t* rusb = RUSB2_REG(rhport);
 
   dcd_int_disable(rhport);
@@ -870,8 +871,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t to
   return r;
 }
 
-bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   // USB buffers always work in bytes so to avoid unnecessary divisions we demand item_size = 1
   TU_ASSERT(ff->item_size == 1);
   rusb2_reg_t* rusb = RUSB2_REG(rhport);
diff --git a/src/portable/sony/cxd56/dcd_cxd56.c b/src/portable/sony/cxd56/dcd_cxd56.c
index a13cd152c4..be694edfa0 100644
--- a/src/portable/sony/cxd56/dcd_cxd56.c
+++ b/src/portable/sony/cxd56/dcd_cxd56.c
@@ -358,8 +358,9 @@ void dcd_edpt_close_all (uint8_t rhport)
   // TODO implement dcd_edpt_close_all()
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   bool ret = true;
diff --git a/src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c b/src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c
index ed823a832f..381aa0b400 100644
--- a/src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c
+++ b/src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c
@@ -246,7 +246,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr) {
   (void)dev_addr;
 
   // Respond with status
-  dcd_edpt_xfer(rhport, TUSB_DIR_IN_MASK | 0x00, NULL, 0);
+  dcd_edpt_xfer(rhport, TUSB_DIR_IN_MASK | 0x00, NULL, 0, false);
 
   // DCD can only set address after status for this request is complete.
   // do it at dcd_edpt0_status_complete()
@@ -788,7 +788,8 @@ static bool edpt_xfer(uint8_t rhport, uint8_t ep_num, tusb_dir_t dir) {
   return true;
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   uint8_t const ep_num = tu_edpt_number(ep_addr);
   tusb_dir_t const dir = tu_edpt_dir(ep_addr);
   xfer_ctl_t *xfer = xfer_ctl_ptr(ep_num, dir);
@@ -801,7 +802,8 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
   return edpt_xfer(rhport, ep_num, dir);
 }
 
-bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t *ff, uint16_t total_bytes) {
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   uint8_t const ep_num = tu_edpt_number(ep_addr);
   tusb_dir_t const dir = tu_edpt_dir(ep_addr);
   xfer_ctl_t *xfer = xfer_ctl_ptr(ep_num, dir);
diff --git a/src/portable/sunxi/dcd_sunxi_musb.c b/src/portable/sunxi/dcd_sunxi_musb.c
index f1f4897cbc..46d05e3e6a 100644
--- a/src/portable/sunxi/dcd_sunxi_musb.c
+++ b/src/portable/sunxi/dcd_sunxi_musb.c
@@ -1083,8 +1083,9 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr)
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   bool ret;
   // TU_LOG1("X %x %d\r\n", ep_addr, total_bytes);
@@ -1102,8 +1103,9 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t t
 }
 
 // Submit a transfer where is managed by FIFO, When complete dcd_event_xfer_complete() is invoked to notify the stack - optional, however, must be listed in usbd.c
-bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   bool ret;
   // TU_LOG1("X %x %d\r\n", ep_addr, total_bytes);
diff --git a/src/portable/synopsys/dwc2/dcd_dwc2.c b/src/portable/synopsys/dwc2/dcd_dwc2.c
index f1e4dbd77e..ad78708b6b 100644
--- a/src/portable/synopsys/dwc2/dcd_dwc2.c
+++ b/src/portable/synopsys/dwc2/dcd_dwc2.c
@@ -456,7 +456,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr) {
   dwc2->dcfg = (dwc2->dcfg & ~DCFG_DAD_Msk) | (dev_addr << DCFG_DAD_Pos);
 
   // Response with status after changing device address
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport) {
@@ -577,13 +577,14 @@ bool dcd_edpt_iso_activate(uint8_t rhport,  tusb_desc_endpoint_t const * p_endpo
   return true;
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   uint8_t const epnum = tu_edpt_number(ep_addr);
   uint8_t const dir = tu_edpt_dir(ep_addr);
   xfer_ctl_t* xfer = XFER_CTL_BASE(epnum, dir);
   bool ret;
 
-  usbd_spin_lock(false);
+  usbd_spin_lock(is_isr);
 
   if (xfer->max_size == 0) {
     ret = false;  // Endpoint is closed
@@ -602,7 +603,7 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t to
     ret = true;
   }
 
-  usbd_spin_unlock(false);
+  usbd_spin_unlock(is_isr);
 
   return ret;
 }
@@ -611,7 +612,8 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t to
 // bytes should be written and second to keep the return value free to give back a boolean
 // success message. If total_bytes is too big, the FIFO will copy only what is available
 // into the USB buffer!
-bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_t total_bytes) {
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   // USB buffers always work in bytes so to avoid unnecessary divisions we demand item_size = 1
   TU_ASSERT(ff->item_size == 1);
 
@@ -620,7 +622,7 @@ bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_t
   xfer_ctl_t* xfer = XFER_CTL_BASE(epnum, dir);
   bool ret;
 
-  usbd_spin_lock(false);
+  usbd_spin_lock(is_isr);
 
   if (xfer->max_size == 0) {
     ret = false;  // Endpoint is closed
@@ -635,7 +637,7 @@ bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t* ff, uint16_t
     ret = true;
   }
 
-  usbd_spin_unlock(false);
+  usbd_spin_unlock(is_isr);
 
   return ret;
 }
diff --git a/src/portable/template/dcd_template.c b/src/portable/template/dcd_template.c
index 3738ac0cb9..90c672d19c 100644
--- a/src/portable/template/dcd_template.c
+++ b/src/portable/template/dcd_template.c
@@ -113,7 +113,8 @@ void dcd_edpt_close_all (uint8_t rhport) {
 }
 
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   (void) rhport;
   (void) ep_addr;
   (void) buffer;
@@ -122,7 +123,8 @@ bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t
 }
 
 // Submit a transfer where is managed by FIFO, When complete dcd_event_xfer_complete() is invoked to notify the stack - optional, however, must be listed in usbd.c
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes) {
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   (void) rhport;
   (void) ep_addr;
   (void) ff;
diff --git a/src/portable/ti/msp430x5xx/dcd_msp430x5xx.c b/src/portable/ti/msp430x5xx/dcd_msp430x5xx.c
index 64cbc50873..10c7d78c5b 100644
--- a/src/portable/ti/msp430x5xx/dcd_msp430x5xx.c
+++ b/src/portable/ti/msp430x5xx/dcd_msp430x5xx.c
@@ -219,7 +219,7 @@ void dcd_set_address (uint8_t rhport, uint8_t dev_addr)
   USBFUNADR = dev_addr;
 
   // Response with status after changing device address
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport)
@@ -344,8 +344,9 @@ void dcd_edpt_close_all (uint8_t rhport)
   // TODO implement dcd_edpt_close_all()
 }
 
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
@@ -393,8 +394,9 @@ bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t
 }
 
 #if 0 // TODO support dcd_edpt_xfer_fifo API
-bool dcd_edpt_xfer_fifo (uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes)
+bool dcd_edpt_xfer_fifo(uint8_t rhport, uint8_t ep_addr, tu_fifo_t * ff, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void) rhport;
 
   uint8_t const epnum = tu_edpt_number(ep_addr);
diff --git a/src/portable/valentyusb/eptri/dcd_eptri.c b/src/portable/valentyusb/eptri/dcd_eptri.c
index a03c945589..760f3c90a5 100644
--- a/src/portable/valentyusb/eptri/dcd_eptri.c
+++ b/src/portable/valentyusb/eptri/dcd_eptri.c
@@ -375,7 +375,7 @@ void dcd_int_disable(uint8_t rhport)
 void dcd_set_address(uint8_t rhport, uint8_t dev_addr)
 {
   // Respond with ACK status first before changing device address
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
 
   // Wait for the response packet to get sent
   while (tx_active)
@@ -475,8 +475,9 @@ void dcd_edpt_clear_stall(uint8_t rhport, uint8_t ep_addr)
   // IN endpoints will get un-stalled when more data is written.
 }
 
-bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes)
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr)
 {
+  (void) is_isr;
   (void)rhport;
   uint8_t ep_num = tu_edpt_number(ep_addr);
   uint8_t ep_dir = tu_edpt_dir(ep_addr);
diff --git a/src/portable/wch/dcd_ch32_usbfs.c b/src/portable/wch/dcd_ch32_usbfs.c
index c248ba14e0..eb2ebd8683 100644
--- a/src/portable/wch/dcd_ch32_usbfs.c
+++ b/src/portable/wch/dcd_ch32_usbfs.c
@@ -218,7 +218,7 @@ void dcd_int_disable(uint8_t rhport) {
 
 void dcd_set_address(uint8_t rhport, uint8_t dev_addr) {
   (void) dev_addr;
-  dcd_edpt_xfer(rhport, 0x80, NULL, 0); // zlp status response
+  dcd_edpt_xfer(rhport, 0x80, NULL, 0, false); // zlp status response
 }
 
 void dcd_remote_wakeup(uint8_t rhport) {
@@ -289,7 +289,8 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr) {
   // TODO optional
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   (void) rhport;
   uint8_t ep = tu_edpt_number(ep_addr);
   uint8_t dir = tu_edpt_dir(ep_addr);
diff --git a/src/portable/wch/dcd_ch32_usbhs.c b/src/portable/wch/dcd_ch32_usbhs.c
index 4a208b9df4..a18eb3e810 100644
--- a/src/portable/wch/dcd_ch32_usbhs.c
+++ b/src/portable/wch/dcd_ch32_usbhs.c
@@ -203,7 +203,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr) {
   (void) dev_addr;
 
   // Response with zlp status
-  dcd_edpt_xfer(rhport, 0x80, NULL, 0);
+  dcd_edpt_xfer(rhport, 0x80, NULL, 0, false);
 }
 
 void dcd_remote_wakeup(uint8_t rhport) {
@@ -315,7 +315,8 @@ void dcd_edpt_clear_stall(uint8_t rhport, uint8_t ep_addr) {
   }
 }
 
-bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes, bool is_isr) {
+  (void) is_isr;
   (void) rhport;
   uint8_t const ep_num = tu_edpt_number(ep_addr);
   tusb_dir_t const dir = tu_edpt_dir(ep_addr);
diff --git a/src/tusb.c b/src/tusb.c
index 083e6d8613..7f451ee70e 100644
--- a/src/tusb.c
+++ b/src/tusb.c
@@ -378,7 +378,7 @@ TU_ATTR_ALWAYS_INLINE static inline bool stream_xfer(uint8_t hwid, tu_edpt_strea
     #endif
   } else {
     #if CFG_TUD_ENABLED
-    return usbd_edpt_xfer(hwid, s->ep_addr, count ? s->ep_buf : NULL, count);
+    return usbd_edpt_xfer(hwid, s->ep_addr, count ? s->ep_buf : NULL, count, false);
     #endif
   }
   return false;
diff --git a/test/fuzz/dcd_fuzz.cc b/test/fuzz/dcd_fuzz.cc
index 046a90555b..7a5d51623a 100644
--- a/test/fuzz/dcd_fuzz.cc
+++ b/test/fuzz/dcd_fuzz.cc
@@ -104,7 +104,7 @@ void dcd_set_address(uint8_t rhport, uint8_t dev_addr) {
   UNUSED(rhport);
   state.address = dev_addr;
   // Respond with status.
-  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0);
+  dcd_edpt_xfer(rhport, tu_edpt_addr(0, TUSB_DIR_IN), NULL, 0, false);
   return;
 }
 
@@ -160,10 +160,11 @@ void dcd_edpt_close(uint8_t rhport, uint8_t ep_addr) {
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to
 // notify the stack
 bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer,
-                   uint16_t total_bytes) {
+                   uint16_t total_bytes, bool is_isr) {
   UNUSED(rhport);
   UNUSED(buffer);
   UNUSED(total_bytes);
+  UNUSED(is_isr);
 
   uint8_t const dir = tu_edpt_dir(ep_addr);
 
diff --git a/test/unit-test/test/device/msc/test_msc_device.c b/test/unit-test/test/device/msc/test_msc_device.c
index 49843a921a..ea02b7050a 100644
--- a/test/unit-test/test/device/msc/test_msc_device.c
+++ b/test/unit-test/test/device/msc/test_msc_device.c
@@ -256,7 +256,7 @@ void test_msc(void)
   dcd_edpt_open_ExpectAndReturn(rhport, (tusb_desc_endpoint_t const *) tu_desc_next(desc_ep), true);
 
   // Prepare SCSI command
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_OUT, NULL, sizeof(msc_cbw_t), true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_OUT, NULL, sizeof(msc_cbw_t), false, true);
   dcd_edpt_xfer_IgnoreArg_buffer();
   dcd_edpt_xfer_ReturnMemThruPtr_buffer( (uint8_t*) &cbw_read10, sizeof(msc_cbw_t));
 
@@ -264,20 +264,20 @@ void test_msc(void)
   dcd_event_xfer_complete(rhport, EDPT_MSC_OUT, sizeof(msc_cbw_t), 0, true);
 
   // control status
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_IN, NULL, 0, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_IN, NULL, 0, false, true);
 
   // SCSI Data transfer
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_IN, NULL, 512, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_IN, NULL, 512, false, true);
   dcd_edpt_xfer_IgnoreArg_buffer();
   dcd_event_xfer_complete(rhport, EDPT_MSC_IN, 512, 0, true); // complete
 
   // SCSI Status
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_IN, NULL, 13, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_IN, NULL, 13, false, true);
   dcd_edpt_xfer_IgnoreArg_buffer();
   dcd_event_xfer_complete(rhport, EDPT_MSC_IN, 13, 0, true);
 
   // Prepare for next command
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_OUT, NULL, sizeof(msc_cbw_t), true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_MSC_OUT, NULL, sizeof(msc_cbw_t), false, true);
   dcd_edpt_xfer_IgnoreArg_buffer();
 
   tud_task();
diff --git a/test/unit-test/test/device/usbd/test_usbd.c b/test/unit-test/test/device/usbd/test_usbd.c
index f0153da3f2..3a2cf32178 100644
--- a/test/unit-test/test/device/usbd/test_usbd.c
+++ b/test/unit-test/test/device/usbd/test_usbd.c
@@ -151,11 +151,11 @@ void test_usbd_get_device_descriptor(void)
   dcd_event_setup_received(rhport, (uint8_t*) &req_get_desc_device, false);
 
   // data
-  dcd_edpt_xfer_ExpectWithArrayAndReturn(rhport, 0x80, (uint8_t*)&data_desc_device, sizeof(tusb_desc_device_t), sizeof(tusb_desc_device_t), true);
+  dcd_edpt_xfer_ExpectWithArrayAndReturn(rhport, 0x80, (uint8_t*)&data_desc_device, sizeof(tusb_desc_device_t), sizeof(tusb_desc_device_t), false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_IN, sizeof(tusb_desc_device_t), 0, false);
 
   // status
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_OUT, NULL, 0, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_OUT, NULL, 0, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_OUT, 0, 0, false);
   dcd_edpt0_status_complete_ExpectWithArray(rhport, &req_get_desc_device, 1);
 
@@ -184,11 +184,11 @@ void test_usbd_get_configuration_descriptor(void)
   dcd_event_setup_received(rhport, (uint8_t*) &req_get_desc_configuration, false);
 
   // data
-  dcd_edpt_xfer_ExpectWithArrayAndReturn(rhport, 0x80, (uint8_t*) data_desc_configuration, total_len, total_len, true);
+  dcd_edpt_xfer_ExpectWithArrayAndReturn(rhport, 0x80, (uint8_t*) data_desc_configuration, total_len, total_len, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_IN, total_len, 0, false);
 
   // status
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_OUT, NULL, 0, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_OUT, NULL, 0, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_OUT, 0, 0, false);
   dcd_edpt0_status_complete_ExpectWithArray(rhport, &req_get_desc_configuration, 1);
 
@@ -227,20 +227,20 @@ void test_usbd_control_in_zlp(void)
 
   // 1st transaction
   dcd_edpt_xfer_ExpectWithArrayAndReturn(rhport, EDPT_CTRL_IN,
-                                         zlp_desc_configuration, CFG_TUD_ENDPOINT0_SIZE, CFG_TUD_ENDPOINT0_SIZE, true);
+                                         zlp_desc_configuration, CFG_TUD_ENDPOINT0_SIZE, CFG_TUD_ENDPOINT0_SIZE, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_IN, CFG_TUD_ENDPOINT0_SIZE, 0, false);
 
   // 2nd transaction
   dcd_edpt_xfer_ExpectWithArrayAndReturn(rhport, EDPT_CTRL_IN,
-                                         zlp_desc_configuration + CFG_TUD_ENDPOINT0_SIZE, CFG_TUD_ENDPOINT0_SIZE, CFG_TUD_ENDPOINT0_SIZE, true);
+                                         zlp_desc_configuration + CFG_TUD_ENDPOINT0_SIZE, CFG_TUD_ENDPOINT0_SIZE, CFG_TUD_ENDPOINT0_SIZE, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_IN, CFG_TUD_ENDPOINT0_SIZE, 0, false);
 
   // Expect Zero length Packet
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_IN, NULL, 0, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_IN, NULL, 0, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_IN, 0, 0, false);
 
   // Status
-  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_OUT, NULL, 0, true);
+  dcd_edpt_xfer_ExpectAndReturn(rhport, EDPT_CTRL_OUT, NULL, 0, false, true);
   dcd_event_xfer_complete(rhport, EDPT_CTRL_OUT, 0, 0, false);
   dcd_edpt0_status_complete_ExpectWithArray(rhport, &req_get_desc_configuration, 1);