diff --git a/src/portable/espressif/esp32s2/dcd_esp32s2.c b/src/portable/espressif/esp32s2/dcd_esp32s2.c
index 72fb4ba4..25e54418 100644
--- a/src/portable/espressif/esp32s2/dcd_esp32s2.c
+++ b/src/portable/espressif/esp32s2/dcd_esp32s2.c
@@ -321,6 +321,7 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 
   xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, dir);
   xfer->buffer       = buffer;
+  xfer->ff           = NULL;
   xfer->total_len    = total_bytes;
   xfer->queued_len   = 0;
   xfer->short_packet = false;
@@ -523,7 +524,12 @@ static void receive_packet(xfer_ctl_t *xfer, /* usb_out_endpoint_t * out_ep, */
   }
 
   // Common buffer read
-  if (xfer->buffer)
+  if (xfer->ff)
+  {
+    // Ring buffer
+    tu_fifo_write_n(xfer->ff, (const void *) rx_fifo, to_recv_size);
+  }
+  else
   {
     uint8_t to_recv_rem = to_recv_size % 4;
     uint16_t to_recv_size_aligned = to_recv_size - to_recv_rem;
@@ -556,12 +562,6 @@ static void receive_packet(xfer_ctl_t *xfer, /* usb_out_endpoint_t * out_ep, */
         last_32b_bound[2] = (tmp & 0x00FF0000) >> 16;
       }
     }
-
-  }
-  else
-  {
-    // Ring buffer
-    tu_fifo_write_n(xfer->ff, (const void *) rx_fifo, to_recv_size);
   }
 
   xfer->queued_len += xfer_size;
@@ -581,7 +581,11 @@ static void transmit_packet(xfer_ctl_t *xfer, volatile usb_in_endpoint_t *in_ep,
 
   uint16_t to_xfer_size = (remaining > xfer->max_size) ? xfer->max_size : remaining;
 
-  if (xfer->buffer)
+  if (xfer->ff)
+  {
+    tu_fifo_read_n(xfer->ff, (void *) tx_fifo, to_xfer_size);
+  }
+  else
   {
     uint8_t to_xfer_rem = to_xfer_size % 4;
     uint16_t to_xfer_size_aligned = to_xfer_size - to_xfer_rem;
@@ -616,10 +620,6 @@ static void transmit_packet(xfer_ctl_t *xfer, volatile usb_in_endpoint_t *in_ep,
       (*tx_fifo) = tmp;
     }
   }
-  else
-  {
-    tu_fifo_read_n(xfer->ff, (void *) tx_fifo, to_xfer_size);
-  }
 }
 
 static void read_rx_fifo(void)
diff --git a/src/portable/microchip/samg/dcd_samg.c b/src/portable/microchip/samg/dcd_samg.c
index 6e7e84a9..12b2633a 100644
--- a/src/portable/microchip/samg/dcd_samg.c
+++ b/src/portable/microchip/samg/dcd_samg.c
@@ -61,6 +61,7 @@ void xfer_epsize_set(xfer_desc_t* xfer, uint16_t epsize)
 void xfer_begin(xfer_desc_t* xfer, uint8_t * buffer, uint16_t total_bytes)
 {
   xfer->buffer     = buffer;
+  xfer->ff         = NULL;
   xfer->total_len  = total_bytes;
   xfer->actual_len = 0;
 }
@@ -68,6 +69,7 @@ void xfer_begin(xfer_desc_t* xfer, uint8_t * buffer, uint16_t total_bytes)
 void xfer_end(xfer_desc_t* xfer)
 {
   xfer->buffer     = NULL;
+  xfer->ff         = NULL;
   xfer->total_len  = 0;
   xfer->actual_len = 0;
 }
@@ -82,7 +84,7 @@ void xfer_packet_done(xfer_desc_t* xfer)
 {
   uint16_t const xact_len = xfer_packet_len(xfer);
 
-  if (xfer->buffer) xfer->buffer += xact_len;
+  xfer->buffer += xact_len;
   xfer->actual_len += xact_len;
 }
 
@@ -436,13 +438,13 @@ void dcd_int_handler(uint8_t rhport)
         if (xact_len)
         {
           // write to EP fifo
-          if (xfer->buffer)
+          if (xfer->ff)
           {
-            xact_ep_write(epnum, xfer->buffer, xact_len);
+            tu_fifo_read_n(ff, (void *) &UDP->UDP_FDR[epnum], xact_len);
           }
           else
           {
-            tu_fifo_read_n(ff, (void *) &UDP->UDP_FDR[epnum], xact_len);
+            xact_ep_write(epnum, xfer->buffer, xact_len);
           }
 
           // TX ready for transfer
@@ -469,13 +471,13 @@ void dcd_int_handler(uint8_t rhport)
         uint16_t const xact_len = (uint16_t) ((UDP->UDP_CSR[epnum] & UDP_CSR_RXBYTECNT_Msk) >> UDP_CSR_RXBYTECNT_Pos);
 
         // Read from EP fifo
-        if (xfer->buffer)
+        if (xfer->ff)
         {
-          xact_ep_read(epnum, xfer->buffer, xact_len);
+          tu_fifo_write_n(xfer->ff, (const void *) &UDP->UDP_FDR[epnum], xact_len);
         }
         else
         {
-          tu_fifo_write_n(xfer->ff, (const void *) &UDP->UDP_FDR[epnum], xact_len);
+          xact_ep_read(epnum, xfer->buffer, xact_len);
         }
 
         xfer_packet_done(xfer);
diff --git a/src/portable/nuvoton/nuc120/dcd_nuc120.c b/src/portable/nuvoton/nuc120/dcd_nuc120.c
index 0c3bd9a6..9ff34e76 100644
--- a/src/portable/nuvoton/nuc120/dcd_nuc120.c
+++ b/src/portable/nuvoton/nuc120/dcd_nuc120.c
@@ -144,13 +144,13 @@ static void dcd_in_xfer(struct xfer_ctl_t *xfer, USBD_EP_T *ep)
 {
   uint16_t bytes_now = tu_min16(xfer->in_remaining_bytes, xfer->max_packet_size);
 
-  if (xfer->data_ptr)
+  if (xfer->ff)
   {
-    memcpy((uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), xfer->data_ptr, bytes_now);
+    tu_fifo_read_n(xfer->ff, (void *) (USBD_BUF_BASE + ep->BUFSEG), bytes_now);
   }
   else
   {
-    tu_fifo_read_n(xfer->ff, (void *) (USBD_BUF_BASE + ep->BUFSEG), bytes_now);
+    memcpy((uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), xfer->data_ptr, bytes_now);
   }
 
   ep->MXPLD = bytes_now;
@@ -277,6 +277,7 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 
   /* store away the information we'll needing now and later */
   xfer->data_ptr = buffer;
+  xfer->ff       = NULL;
   xfer->in_remaining_bytes = total_bytes;
   xfer->total_bytes = total_bytes;
 
@@ -429,14 +430,14 @@ void dcd_int_handler(uint8_t rhport)
         if (out_ep)
         {
           /* copy the data from the PC to the previously provided buffer */
-          if (xfer->data_ptr)
+          if (xfer->ff)
           {
-            memcpy(xfer->data_ptr, (uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), available_bytes);
-            xfer->data_ptr += available_bytes;
+            tu_fifo_write_n(xfer->ff, (const void *) (USBD_BUF_BASE + ep->BUFSEG), available_bytes);
           }
           else
           {
-            tu_fifo_write_n(xfer->ff, (const void *) (USBD_BUF_BASE + ep->BUFSEG), available_bytes);
+            memcpy(xfer->data_ptr, (uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), available_bytes);
+            xfer->data_ptr += available_bytes;
           }
 
           xfer->out_bytes_so_far += available_bytes;
@@ -452,8 +453,7 @@ void dcd_int_handler(uint8_t rhport)
           /* update the bookkeeping to reflect the data that has now been sent to the PC */
           xfer->in_remaining_bytes -= available_bytes;
 
-          /* increment only if xfer->data_ptr != NULL - if xfer->data_ptr == NULL then a FIFO is used for which xfer->data_ptr MUST STAY ZERO! */
-          if (xfer->data_ptr) xfer->data_ptr += available_bytes;
+          xfer->data_ptr += available_bytes;
 
           /* if more data to send, send it; otherwise, alert TinyUSB that we've finished */
           if (xfer->in_remaining_bytes)
diff --git a/src/portable/nuvoton/nuc121/dcd_nuc121.c b/src/portable/nuvoton/nuc121/dcd_nuc121.c
index 1560d564..a689470d 100644
--- a/src/portable/nuvoton/nuc121/dcd_nuc121.c
+++ b/src/portable/nuvoton/nuc121/dcd_nuc121.c
@@ -144,13 +144,13 @@ static void dcd_in_xfer(struct xfer_ctl_t *xfer, USBD_EP_T *ep)
 {
   uint16_t bytes_now = tu_min16(xfer->in_remaining_bytes, xfer->max_packet_size);
 
-  if (xfer->data_ptr)
+  if (xfer->ff)
   {
-    memcpy((uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), xfer->data_ptr, bytes_now);
+    tu_fifo_read_n(xfer->ff, (void *) (USBD_BUF_BASE + ep->BUFSEG), bytes_now);
   }
   else
   {
-    tu_fifo_read_n(xfer->ff, (void *) (USBD_BUF_BASE + ep->BUFSEG), bytes_now);
+    memcpy((uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), xfer->data_ptr, bytes_now);
   }
 
   ep->MXPLD = bytes_now;
@@ -281,6 +281,7 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 
   /* store away the information we'll needing now and later */
   xfer->data_ptr = buffer;
+  xfer->ff       = NULL;
   xfer->in_remaining_bytes = total_bytes;
   xfer->total_bytes = total_bytes;
 
@@ -438,14 +439,14 @@ void dcd_int_handler(uint8_t rhport)
         if (out_ep)
         {
           /* copy the data from the PC to the previously provided buffer */
-          if (xfer->data_ptr)
+          if (xfer->ff)
           {
-            memcpy(xfer->data_ptr, (uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), available_bytes);
-            xfer->data_ptr += available_bytes;
+            tu_fifo_write_n(xfer->ff, (const void *) (USBD_BUF_BASE + ep->BUFSEG), available_bytes);
           }
           else
           {
-            tu_fifo_write_n(xfer->ff, (const void *) (USBD_BUF_BASE + ep->BUFSEG), available_bytes);
+            memcpy(xfer->data_ptr, (uint8_t *)(USBD_BUF_BASE + ep->BUFSEG), available_bytes);
+            xfer->data_ptr += available_bytes;
           }
 
           xfer->out_bytes_so_far += available_bytes;
@@ -460,7 +461,7 @@ void dcd_int_handler(uint8_t rhport)
         {
           /* update the bookkeeping to reflect the data that has now been sent to the PC */
           xfer->in_remaining_bytes -= available_bytes;
-          if (xfer->data_ptr) xfer->data_ptr += available_bytes;
+          xfer->data_ptr += available_bytes;
 
           /* if more data to send, send it; otherwise, alert TinyUSB that we've finished */
           if (xfer->in_remaining_bytes)
diff --git a/src/portable/nuvoton/nuc505/dcd_nuc505.c b/src/portable/nuvoton/nuc505/dcd_nuc505.c
index 92656488..3641b704 100644
--- a/src/portable/nuvoton/nuc505/dcd_nuc505.c
+++ b/src/portable/nuvoton/nuc505/dcd_nuc505.c
@@ -181,7 +181,11 @@ static void dcd_userEP_in_xfer(struct xfer_ctl_t *xfer, USBD_EP_T *ep)
   }
 
   /* provided buffers are thankfully 32-bit aligned, allowing most data to be transfered as 32-bit */
-  if (xfer->data_ptr)
+  if (xfer->ff)
+  {
+    tu_fifo_read_n(xfer->ff, (void *) (ep->EPDAT_BYTE), bytes_now);
+  }
+  else
   {
     uint16_t countdown = bytes_now;
     while (countdown > 3)
@@ -195,10 +199,6 @@ static void dcd_userEP_in_xfer(struct xfer_ctl_t *xfer, USBD_EP_T *ep)
     while (countdown--)
       ep->EPDAT_BYTE = *xfer->data_ptr++;
   }
-  else
-  {
-    tu_fifo_read_n(xfer->ff, (void *) (ep->EPDAT_BYTE), bytes_now);
-  }
 
   /* for short packets, we must nudge the peripheral to say 'that's all folks' */
   if (bytes_now != xfer->max_packet_size)
@@ -394,6 +394,7 @@ bool dcd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t *buffer, uint16_t to
 
     /* store away the information we'll needing now and later */
     xfer->data_ptr = buffer;
+    xfer->ff       = NULL;
     xfer->in_remaining_bytes = total_bytes;
     xfer->total_bytes = total_bytes;
 
@@ -656,14 +657,15 @@ void dcd_int_handler(uint8_t rhport)
 #else
           uint16_t const available_bytes = ep->EPDATCNT & USBD_EPDATCNT_DATCNT_Msk;
           /* copy the data from the PC to the previously provided buffer */
-          if (xfer->data_ptr)
+          if (xfer->ff)
           {
-            for (int count = 0; (count < available_bytes) && (xfer->out_bytes_so_far < xfer->total_bytes); count++, xfer->out_bytes_so_far++)
-              *xfer->data_ptr++ = ep->EPDAT_BYTE;
+            tu_fifo_write_n(xfer->ff, (const void *) &ep->EPDAT_BYTE, tu_min16(available_bytes, xfer->total_bytes - xfer->out_bytes_so_far));
           }
           else
           {
-            tu_fifo_write_n(xfer->ff, (const void *) &ep->EPDAT_BYTE, tu_min16(available_bytes, xfer->total_bytes - xfer->out_bytes_so_far));
+            for (int count = 0; (count < available_bytes) && (xfer->out_bytes_so_far < xfer->total_bytes); count++, xfer->out_bytes_so_far++)
+              *xfer->data_ptr++ = ep->EPDAT_BYTE;
+
           }
 
           /* when the transfer is finished, alert TinyUSB; otherwise, continue accepting more data */
diff --git a/src/portable/st/synopsys/dcd_synopsys.c b/src/portable/st/synopsys/dcd_synopsys.c
index b6dacd92..5f8c4463 100644
--- a/src/portable/st/synopsys/dcd_synopsys.c
+++ b/src/portable/st/synopsys/dcd_synopsys.c
@@ -646,6 +646,7 @@ bool dcd_edpt_xfer (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t
 
   xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, dir);
   xfer->buffer      = buffer;
+  xfer->ff          = NULL;
   xfer->total_len   = total_bytes;
 
   // EP0 can only handle one packet
@@ -908,7 +909,12 @@ static void handle_rxflvl_ints(uint8_t rhport, USB_OTG_OUTEndpointTypeDef * out_
       xfer_ctl_t * xfer = XFER_CTL_BASE(epnum, TUSB_DIR_OUT);
 
       // Read packet off RxFIFO
-      if (xfer->buffer)
+      if (xfer->ff)
+      {
+        // Ring buffer
+        tu_fifo_write_n(xfer->ff, (const void *) rx_fifo, bcnt);
+      }
+      else
       {
         // Linear buffer
         read_fifo_packet(rhport, xfer->buffer, bcnt);
@@ -916,11 +922,6 @@ static void handle_rxflvl_ints(uint8_t rhport, USB_OTG_OUTEndpointTypeDef * out_
         // Increment pointer to xfer data
         xfer->buffer += bcnt;
       }
-      else
-      {
-        // Ring buffer
-        tu_fifo_write_n(xfer->ff, (const void *) rx_fifo, bcnt);
-      }
 
       // Truncate transfer length in case of short packet
       if(bcnt < xfer->max_size) {
@@ -1028,18 +1029,18 @@ static void handle_epin_ints(uint8_t rhport, USB_OTG_DeviceTypeDef * dev, USB_OT
           }
 
           // Push packet to Tx-FIFO
-          if (xfer->buffer)
+          if (xfer->ff)
+          {
+            usb_fifo_t tx_fifo = FIFO_BASE(rhport, n);
+            tu_fifo_read_n(xfer->ff, (void *) tx_fifo, packet_size);
+          }
+          else
           {
             write_fifo_packet(rhport, n, xfer->buffer, packet_size);
 
             // Increment pointer to xfer data
             xfer->buffer += packet_size;
           }
-          else
-          {
-            usb_fifo_t tx_fifo = FIFO_BASE(rhport, n);
-            tu_fifo_read_n(xfer->ff, (void *) tx_fifo, packet_size);
-          }
         }
 
         // Turn off TXFE if all bytes are written.