diff --git a/arch/arm/src/sama5/sam_udphs.c b/arch/arm/src/sama5/sam_udphs.c
index 54aa82d63bd..39f72d63ff1 100644
--- a/arch/arm/src/sama5/sam_udphs.c
+++ b/arch/arm/src/sama5/sam_udphs.c
@@ -969,11 +969,20 @@ static void sam_dma_wrsetup(struct sam_usbdev_s *priv, struct sam_ep_s *privep,
       if (remaining > DMA_MAX_FIFO_SIZE)
         {
           privreq->inflight = DMA_MAX_FIFO_SIZE;
+          privep->zlpneeded = false;
         }
       else
 #endif
         {
           privreq->inflight = remaining;
+
+          /* If the size is an exact multple of full packets, then note if
+           * we need to send a zero length packet next.
+           */
+
+          privep->zlpneeded =
+            ((privreq->req.flags & USBDEV_REQFLAGS_NULLPKT) != 0 &&
+             (remaining % privep->ep.maxpacket) == 0);
         }
 
       /* And perform the single DMA transfer.
@@ -1223,9 +1232,19 @@ static void sam_req_wrsetup(struct sam_usbdev_s *priv,
    * the request.
    */
 
-  if (nbytes >= privep->ep.maxpacket)
+  privep->zlpneeded = false;
+  if (nbytes > privep->ep.maxpacket)
     {
-      nbytes =  privep->ep.maxpacket;
+      nbytes = privep->ep.maxpacket;
+    }
+  else if (nbytes == privep->ep.maxpacket)
+    {
+      /* If the size is exactly a full packet, then note if we need to
+       * send a zero length packet next.
+       */
+
+      privep->zlpneeded =
+        ((privreq->req.flags & USBDEV_REQFLAGS_NULLPKT) != 0);
     }
 
   /* This is the new number of bytes "in-flight" */
@@ -1352,26 +1371,6 @@ static int sam_req_write(struct sam_usbdev_s *priv, struct sam_ep_s *privep)
       bytesleft = privreq->req.len - privreq->req.xfrd;
       if (bytesleft > 0)
         {
-          /* If the size is exactly a full packet, then note if we need to
-           * send a zero length packet next.
-           */
-
-          if (bytesleft == privep->ep.maxpacket &&
-             (privreq->req.flags & USBDEV_REQFLAGS_NULLPKT) != 0)
-            {
-              /* Next time we get here, bytesleft will be zero and zlpneeded
-               * will be set.
-               */
-
-              privep->zlpneeded = true;
-            }
-          else
-            {
-              /* No zero packet is forthcoming (maybe later) */
-
-              privep->zlpneeded = false;
-            }
-
           /* The way that we handle the transfer is going to depend on
            * whether or not this endpoint supports DMA.  In either case
            * the endpoint state will transition to SENDING.
@@ -2392,6 +2391,12 @@ static void sam_dma_interrupt(struct sam_usbdev_s *priv, int epno)
           /* This is an IN endpoint.  Continuing processing the write
            * request.  We must call sam_req_write in the IDLE state
            * with the number of bytes transferred in 'inflight'
+           *
+           * REVISIT: On the SAMV7, I found that you really need to
+           * wait for the TX completion interrupt before calling
+           * sam_req_write().  For the SAMV7, the logic here just
+           * enables that TX completion interrupt.  The symptom of
+           * the problem was occassional missing zero-length packets.
            */
 
           DEBUGASSERT(USB_ISEPIN(privep->ep.eplog));
@@ -2451,7 +2456,7 @@ static void sam_dma_interrupt(struct sam_usbdev_s *priv, int epno)
                   USB_ISEPOUT(privep->ep.eplog));
 
       /* Get the number of bytes transferred from the DMA status.
-        *
+       *
        * BUFF_COUNT holds the number of untransmitted bytes. In this case,
        * BUFF_COUNT should not be zero.  BUFF_COUNT was set to the
        * 'inflight' count when the DMA started so the difference will
diff --git a/arch/arm/src/samv7/sam_usbdevhs.c b/arch/arm/src/samv7/sam_usbdevhs.c
index 7bb5a1d0b58..f3225c8573c 100644
--- a/arch/arm/src/samv7/sam_usbdevhs.c
+++ b/arch/arm/src/samv7/sam_usbdevhs.c
@@ -1027,7 +1027,7 @@ static void sam_dma_wrsetup(struct sam_usbdev_s *priv, struct sam_ep_s *privep,
         {
           privreq->inflight = remaining;
 
-          /* If the size is an exact multple of full packets, then note if that
+          /* If the size is an exact multple of full packets, then note if
            * we need to send a zero length packet next.
            */
 
@@ -1284,7 +1284,7 @@ static void sam_req_wrsetup(struct sam_usbdev_s *priv,
   privep->zlpneeded = false;
   if (nbytes > privep->ep.maxpacket)
     {
-      nbytes =  privep->ep.maxpacket;
+      nbytes = privep->ep.maxpacket;
     }
   else if (nbytes == privep->ep.maxpacket)
     {
@@ -2497,6 +2497,7 @@ static void sam_dma_interrupt(struct sam_usbdev_s *priv, int epno)
 
           DEBUGASSERT(USB_ISEPIN(privep->ep.eplog));
           sam_putreg(USBHS_DEVEPTINT_TXINI, SAM_USBHS_DEVEPTICR(epno));
+
 #if 1 /* Wait for TXINI */
           sam_putreg(USBHS_DEVEPTINT_TXINI, SAM_USBHS_DEVEPTIER(epno));
 #else