diff --git a/src/class/usbtmc/usbtmc.h b/src/class/usbtmc/usbtmc.h
index 2e4999c2..6893c374 100644
--- a/src/class/usbtmc/usbtmc.h
+++ b/src/class/usbtmc/usbtmc.h
@@ -228,6 +228,15 @@ typedef struct TU_ATTR_PACKED
 
 TU_VERIFY_STATIC(sizeof(usbtmc_get_clear_status_rsp_t) == 2u, "struct wrong length");
 
+// Used for both abort bulk IN and bulk OUT
+typedef struct TU_ATTR_PACKED
+{
+  uint8_t USBTMC_status;
+  uint8_t bTag;
+} usbtmc_initiate_abort_rsp_t;
+
+TU_VERIFY_STATIC(sizeof(usbtmc_get_clear_status_rsp_t) == 2u, "struct wrong length");
+
 typedef struct TU_ATTR_PACKED
 {
   uint8_t USBTMC_status;                 ///< usbtmc_status_enum
diff --git a/src/class/usbtmc/usbtmc_device.c b/src/class/usbtmc/usbtmc_device.c
index cf8a5069..6d562641 100644
--- a/src/class/usbtmc/usbtmc_device.c
+++ b/src/class/usbtmc/usbtmc_device.c
@@ -8,7 +8,7 @@
 /*
  * The MIT License (MIT)
  *
- * Copyright (c) 2019 N Conrad
+ * Copyright (c) 2019 Nathan Conrad
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -33,31 +33,53 @@
 
 #include "tusb_option.h"
 
-// We don't do any cross-task anything here (everything is in tud or interrupt context).
-// You must ensure thread safety in your own app.
+// Synchronization is needed in some spots.
+// These functions should NOT be called from interrupts.
+
+/* The library is designed that its functions can be called by any user task, with need for
+ * additional locking. In the case of "no OS", this task is never preempted other than by
+ * interrupts, and the USBTMC code isn't called by interrupts, so all is OK. In the case
+ * of an OS, this class driver uses the OSAL to perform locking. The code uses a single lock
+ * and does not call outside of this class with a lock held, so deadlocks won't happen.
+ *
+ * This module's application-facing functions are not reentrant. The application must
+ * only call them from a single thread (or implement its own locking).
+ */
 
 
-//Limitations (not planned to be implemented):
-// "vendor-specific" commands are not handled
+//Limitations:
+// "vendor-specific" commands are not handled.
 // Dealing with "termchar" must be handled by the application layer,
 //    though additional error checking is does in this module.
+// talkOnly and listenOnly are NOT supported. They're no permitted
+// in USB488, anyway.
+
+/* Supported:
+ *
+ * Notification pulse
+ * Trigger
+ * Read status byte (both by interrupt endpoint and control message)
+ *
+ */
+
 
 // TODO:
 // USBTMC 3.2.2 error conditions not strictly followed
 // No local lock-out, REN, or GTL.
 // Cannot handle clear.
-// Not all "capabilities" supported
 // Clear message available status byte at the correct time? (488 4.3.1.3)
-// Split transfers
+// Abort bulk in/out
 // No CLEAR_FEATURE/HALT no EP (yet)
-// No aborting transfers.
 
 #if (TUSB_OPT_DEVICE_ENABLED && CFG_TUD_USBTMC)
 
+#include <string.h>
 #include "usbtmc.h"
 #include "usbtmc_device.h"
 #include "device/dcd.h"
 #include "device/usbd.h"
+#include "uart_util.h"
+static char logMsg[150];
 
 // FIXME: I shouldn't need to include _pvt headers.
 #include "device/usbd_pvt.h"
@@ -70,21 +92,31 @@ typedef enum
   STATE_IDLE,
   STATE_RCV,
   STATE_TX_REQUESTED,
-  STATE_TX_INITIATED
+  STATE_TX_INITIATED,
+  STATE_CLEARING,
+  STATE_ABORTING_BULK_IN,
+  STATE_ABORTING_BULK_OUT,
+  STATE_NUM_STATES
 } usbtmcd_state_enum;
 
 typedef struct
 {
-  usbtmcd_state_enum state;
+  volatile usbtmcd_state_enum state;
+
   uint8_t itf_id;
   uint8_t ep_bulk_in;
   uint8_t ep_bulk_out;
   uint8_t ep_int_in;
-  uint8_t ep_bulk_in_buf[64];
-  uint8_t ep_bulk_out_buf[64];
-  uint8_t lastTag;
+  // IN buffer is only used for first packet, not the remainder
+  // in order to deal with prepending header
+  uint8_t ep_bulk_in_buf[USBTMCD_MAX_PACKET_SIZE];
+  // OUT buffer receives one packet at a time
+  uint8_t ep_bulk_out_buf[USBTMCD_MAX_PACKET_SIZE];
+  uint32_t transfer_size_remaining; // also used for requested length for bulk IN.
+
+  uint8_t lastBulkOutTag; // used for aborts (mostly)
+  uint8_t lastBulkInTag; // used for aborts (mostly)
 
-  uint32_t transfer_size_remaining;
   uint8_t const * devInBuffer;
 } usbtmc_interface_state_t;
 
@@ -97,39 +129,63 @@ static usbtmc_interface_state_t usbtmc_state =
     .ep_int_in = 0
 };
 
-// We want everything to fit nicely in a single packet, so lets require EP size >32
-// I'm not sure if this is really necessary, though.
+// We need all headers to fit in a single packet in this implementation.
 TU_VERIFY_STATIC(USBTMCD_MAX_PACKET_SIZE >= 32u,"USBTMC dev EP packet size too small");
-
+TU_VERIFY_STATIC(
+    (sizeof(usbtmc_state.ep_bulk_in_buf) % USBTMCD_MAX_PACKET_SIZE) == 0,
+    "packet buffer must be a multiple of the packet size");
 
 static bool handle_devMsgOutStart(uint8_t rhport, void *data, size_t len);
 static bool handle_devMsgOut(uint8_t rhport, void *data, size_t len, size_t packetLen);
 
+
+osal_mutex_def_t usbtmcLockBuffer;
+static osal_mutex_t usbtmcLock;
+
+// Our own private lock, mostly for the state variable.
+#define criticalEnter() do {osal_mutex_lock(usbtmcLock,OSAL_TIMEOUT_WAIT_FOREVER); } while (0)
+#define criticalLeave() do {osal_mutex_unlock(usbtmcLock); } while (0)
+
 // called from app
 // We keep a reference to the buffer, so it MUST not change until the app is
 // notified that the transfer is complete.
 // length of data is specified in the hdr.
+
+// We can't just send the whole thing at once because we need to concatanate the
+// header with the data.
 bool usbtmcd_transmit_dev_msg_data(
     uint8_t rhport,
-    usbtmc_msg_dev_dep_msg_in_header_t const * hdr,
-    const void *data)
+    const void * data, size_t len,
+    bool usingTermChar)
 {
-  TU_ASSERT(usbtmc_state.state == STATE_TX_REQUESTED);
+  const unsigned int txBufLen = sizeof(usbtmc_state.ep_bulk_in_buf);
+
 #ifndef NDEBUG
-  TU_ASSERT(hdr->TransferSize > 0u);
-  if(hdr->bmTransferAttributes.UsingTermChar)
+  TU_ASSERT(len > 0u);
+  TU_ASSERT(len <= usbtmc_state.transfer_size_remaining);
+  if(usingTermChar)
   {
     TU_ASSERT(usbtmcd_app_capabilities.bmDevCapabilities.canEndBulkInOnTermChar);
     TU_ASSERT(termCharRequested);
-    TU_ASSERT(((uint8_t*)data)[hdr->TransferSize-1] == termChar);
+    TU_ASSERT(((uint8_t*)data)[len-1] == termChar);
   }
 #endif
 
+  TU_VERIFY(usbtmc_state.state == STATE_TX_REQUESTED);
+  usbtmc_msg_dev_dep_msg_in_header_t *hdr = (usbtmc_msg_dev_dep_msg_in_header_t*)usbtmc_state.ep_bulk_in_buf;
+  memset(hdr, 0x00, sizeof(*hdr));
+  hdr->header.MsgID = USBTMC_MSGID_DEV_DEP_MSG_IN;
+  hdr->header.bTag = usbtmc_state.lastBulkInTag;
+  hdr->header.bTagInverse = (uint8_t)~(usbtmc_state.lastBulkInTag);
+  hdr->TransferSize = len;
+  hdr->bmTransferAttributes.EOM = 1u;
+  hdr->bmTransferAttributes.UsingTermChar = usingTermChar;
+
   // Copy in the header
-  memcpy(usbtmc_state.ep_bulk_in_buf, hdr, sizeof(*hdr));
   size_t packetLen = sizeof(*hdr);
-  // Single-packet transfer
-  if((packetLen + hdr->TransferSize) <= USBTMCD_MAX_PACKET_SIZE)
+
+  // If it fits in a single trasnmission:
+  if((packetLen + hdr->TransferSize) <= txBufLen)
   {
     memcpy((uint8_t*)(usbtmc_state.ep_bulk_in_buf) + packetLen, data, hdr->TransferSize);
     packetLen = (uint16_t)(packetLen+ hdr->TransferSize);
@@ -142,15 +198,23 @@ bool usbtmcd_transmit_dev_msg_data(
     usbtmc_state.transfer_size_remaining = 0;
     usbtmc_state.devInBuffer = NULL;
   }
-  else
+  else /* partial packet */
   {
-    memcpy((uint8_t*)(usbtmc_state.ep_bulk_in_buf) + packetLen, data, USBTMCD_MAX_PACKET_SIZE - packetLen);
-    usbtmc_state.transfer_size_remaining = hdr->TransferSize - (USBTMCD_MAX_PACKET_SIZE - packetLen);
-    usbtmc_state.devInBuffer += (USBTMCD_MAX_PACKET_SIZE - packetLen);
-    packetLen = USBTMCD_MAX_PACKET_SIZE;
+    memcpy((uint8_t*)(usbtmc_state.ep_bulk_in_buf) + packetLen, data, txBufLen - packetLen);
+    usbtmc_state.devInBuffer += txBufLen - packetLen;
+    usbtmc_state.transfer_size_remaining = hdr->TransferSize - (txBufLen - packetLen);
+    packetLen = txBufLen;
   }
-  usbtmc_state.state = STATE_TX_INITIATED;
-  TU_VERIFY( usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_state.ep_bulk_in_buf,(uint16_t)packetLen));
+
+
+  criticalEnter();
+  {
+    TU_VERIFY(usbtmc_state.state == STATE_TX_REQUESTED);
+    usbtmc_state.state = STATE_TX_INITIATED;
+  }
+  criticalLeave();
+
+  TU_VERIFY( usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_state.ep_bulk_in_buf, (uint16_t)packetLen));
   return true;
 }
 
@@ -158,12 +222,17 @@ void usbtmcd_init(void)
 {
 #ifndef NDEBUG
 #  if USBTMC_CFG_ENABLE_488
-    if(usbtmcd_app_capabilities.bmIntfcCapabilities488.supportsTrigger)
-      TU_ASSERT(&usbtmcd_app_msg_trigger != NULL,);
+  if(usbtmcd_app_capabilities.bmIntfcCapabilities488.supportsTrigger)
+    TU_ASSERT(&usbtmcd_app_msg_trigger != NULL,);
+  // Per USB488 spec: table 8
+  TU_ASSERT(!usbtmcd_app_capabilities.bmIntfcCapabilities.listenOnly,);
+  TU_ASSERT(!usbtmcd_app_capabilities.bmIntfcCapabilities.talkOnly,);
 #  endif
     if(usbtmcd_app_capabilities.bmIntfcCapabilities.supportsIndicatorPulse)
       TU_ASSERT(&usbtmcd_app_indicator_pluse != NULL,);
 #endif
+
+    usbtmcLock = osal_mutex_create(&usbtmcLockBuffer);
 }
 
 bool usbtmcd_open(uint8_t rhport, tusb_desc_interface_t const * itf_desc, uint16_t *p_length)
@@ -226,10 +295,17 @@ bool usbtmcd_open(uint8_t rhport, tusb_desc_interface_t const * itf_desc, uint16
 #ifndef NDEBUG
   TU_ASSERT(usbtmc_state.ep_bulk_in != 0);
   TU_ASSERT(usbtmc_state.ep_bulk_out != 0);
-  if (itf_desc->bNumEndpoints == 2) {
+  if (itf_desc->bNumEndpoints == 2)
+  {
     TU_ASSERT(usbtmc_state.ep_int_in == 0);
   }
-  else if (itf_desc->bNumEndpoints == 2)
+  else if (itf_desc->bNumEndpoints == 3)
+  {
+    TU_ASSERT(usbtmc_state.ep_int_in != 0);
+  }
+
+  if(usbtmcd_app_capabilities.bmIntfcCapabilities488.is488_2 ||
+      usbtmcd_app_capabilities.bmDevCapabilities488.SR1)
   {
     TU_ASSERT(usbtmc_state.ep_int_in != 0);
   }
@@ -286,12 +362,22 @@ static bool handle_devMsgIn(uint8_t rhport, void *data, size_t len)
 {
   TU_VERIFY(len == sizeof(usbtmc_msg_request_dev_dep_in));
   usbtmc_msg_request_dev_dep_in *msg = (usbtmc_msg_request_dev_dep_in*)data;
-  TU_VERIFY(usbtmc_state.state == STATE_IDLE);
-  usbtmc_state.state = STATE_TX_REQUESTED;
-  usbtmc_state.transfer_size_remaining = msg->TransferSize;
+
+  sprintf(logMsg," handle_devMsgIn len=%ul\r\n",len);
+  uart_tx_str_sync(logMsg);
+
+  criticalEnter();
+  {
+    TU_VERIFY(usbtmc_state.state == STATE_IDLE);
+    usbtmc_state.state = STATE_TX_REQUESTED;
+    usbtmc_state.lastBulkInTag = msg->header.bTag;
+    usbtmc_state.transfer_size_remaining = msg->TransferSize;
+  }
+  criticalLeave();
 
   termCharRequested = msg->bmTransferAttributes.TermCharEnabled;
   termChar = msg->TermChar;
+
   if(termCharRequested)
     TU_VERIFY(usbtmcd_app_capabilities.bmDevCapabilities.canEndBulkInOnTermChar);
 
@@ -302,8 +388,17 @@ static bool handle_devMsgIn(uint8_t rhport, void *data, size_t len)
 bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_t xferred_bytes)
 {
   TU_VERIFY(result == XFER_RESULT_SUCCESS);
+  uart_tx_str_sync("USBTMC Xfer CB" );
+  sprintf(logMsg," STATE=%lu ", (uint32_t)usbtmc_state.state);
+  uart_tx_str_sync(logMsg);
+
+  if(usbtmc_state.state == STATE_CLEARING) {
+    return true; /* I think we can ignore everything here */
+  }
+
   if(ep_addr == usbtmc_state.ep_bulk_out)
   {
+    uart_tx_str_sync("OUT");
     switch(usbtmc_state.state)
     {
     case STATE_IDLE:
@@ -312,15 +407,19 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
       uint8_t invInvTag = (uint8_t)~(msg->header.bTagInverse);
       TU_VERIFY(msg->header.bTag == invInvTag);
       TU_VERIFY(msg->header.bTag != 0x00);
-      usbtmc_state.lastTag = msg->header.bTag;
+
+      sprintf(logMsg," type=%lu\r\n",(uint32_t)msg->header.MsgID);
+      uart_tx_str_sync(logMsg);
 
       switch(msg->header.MsgID) {
       case USBTMC_MSGID_DEV_DEP_MSG_OUT:
         TU_VERIFY(handle_devMsgOutStart(rhport, msg, xferred_bytes));
         TU_VERIFY(usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_out, usbtmc_state.ep_bulk_out_buf, USBTMCD_MAX_PACKET_SIZE));
+        usbtmc_state.lastBulkOutTag = msg->header.bTag;
         break;
 
       case USBTMC_MSGID_DEV_DEP_MSG_IN:
+        uart_tx_sync("Handling msg in req\r\n", 21);
         TU_VERIFY(handle_devMsgIn(rhport, msg, xferred_bytes));
         break;
 
@@ -336,6 +435,7 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
       case USBTMC_MSGID_VENDOR_SPECIFIC_MSG_OUT:
       case USBTMC_MSGID_VENDOR_SPECIFIC_IN:
       default:
+
         TU_VERIFY(false);
         return false;
       }
@@ -347,12 +447,22 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
 
     case STATE_TX_REQUESTED:
     case STATE_TX_INITIATED:
+    case STATE_ABORTING_BULK_IN:
+    case STATE_ABORTING_BULK_OUT:
     default:
+      if(msg == NULL)
+        sprintf(logMsg," Unknown received control?\r\n ");
+      else {
+        sprintf(logMsg," msg=%lu\r\n ", (uint32_t)msg->header.MsgID);
+      }
+      uart_tx_str_sync(logMsg);
       TU_VERIFY(false);
     }
   }
   else if(ep_addr == usbtmc_state.ep_bulk_in)
   {
+    sprintf(logMsg,"IN\r\n");
+    uart_tx_str_sync(logMsg);
     TU_ASSERT(usbtmc_state.state == STATE_TX_INITIATED);
     if(usbtmc_state.transfer_size_remaining == 0)
     {
@@ -360,14 +470,14 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint
       TU_VERIFY(usbtmcd_app_msgBulkIn_complete(rhport));
       TU_VERIFY( usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_out, usbtmc_state.ep_bulk_out_buf, USBTMCD_MAX_PACKET_SIZE));
     }
-    else if(usbtmc_state.transfer_size_remaining >= USBTMCD_MAX_PACKET_SIZE)
+    else if(usbtmc_state.transfer_size_remaining > sizeof(usbtmc_state.devInBuffer))
     {
-      memcpy(usbtmc_state.ep_bulk_in_buf, usbtmc_state.devInBuffer, USBTMCD_MAX_PACKET_SIZE);
-      usbtmc_state.devInBuffer += USBTMCD_MAX_PACKET_SIZE;
-      usbtmc_state.transfer_size_remaining -= USBTMCD_MAX_PACKET_SIZE;
-      TU_VERIFY( usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_state.ep_bulk_in_buf,USBTMCD_MAX_PACKET_SIZE));
+      memcpy(usbtmc_state.ep_bulk_in_buf, usbtmc_state.devInBuffer, sizeof(usbtmc_state.ep_bulk_in_buf));
+      usbtmc_state.devInBuffer += sizeof(usbtmc_state.devInBuffer);
+      usbtmc_state.transfer_size_remaining -= sizeof(usbtmc_state.devInBuffer);
+      TU_VERIFY( usbd_edpt_xfer(rhport, usbtmc_state.ep_bulk_in, usbtmc_state.ep_bulk_in_buf,sizeof(usbtmc_state.devInBuffer)));
     }
-    else // short packet
+    else // last packet
     {
       size_t packetLen = usbtmc_state.transfer_size_remaining;
       memcpy(usbtmc_state.ep_bulk_in_buf, usbtmc_state.devInBuffer, usbtmc_state.transfer_size_remaining);
@@ -401,6 +511,7 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
       (request->bRequest == TUSB_REQ_CLEAR_FEATURE) &&
       (request->wValue == TUSB_REQ_FEATURE_EDPT_HALT))
   {
+    uart_tx_str_sync("feature clear\r\n");
     if((request->wIndex) == usbtmc_state.ep_bulk_out)
     {
       usmtmcd_app_bulkOut_clearFeature(rhport);
@@ -426,23 +537,48 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
   // USBTMC required requests
   case USBTMC_bREQUEST_INITIATE_ABORT_BULK_OUT:
   case USBTMC_bREQUEST_CHECK_ABORT_BULK_OUT_STATUS:
-  case USBTMC_bREQUEST_INITIATE_ABORT_BULK_IN:
+  {
+    TU_VERIFY(request->bmRequestType == 0xA2); // in,class,EP
+    TU_VERIFY(request->wLength == 1u);
+    tmcStatusCode = USBTMC_STATUS_FAILED;
+    usbd_edpt_xfer(rhport, 0u, (void*)&tmcStatusCode,sizeof(tmcStatusCode));
+    return true;
+  }
   case USBTMC_bREQUEST_CHECK_ABORT_BULK_IN_STATUS:
-    {
-      TU_VERIFY(request->bmRequestType == 0xA2); // in,class,EP
-      TU_VERIFY(request->wLength == 1u);
-      tmcStatusCode = USBTMC_STATUS_FAILED;
-      usbd_edpt_xfer(rhport, 0u, (void*)&tmcStatusCode,sizeof(tmcStatusCode));
-      return true;
-    }
+  {
+    TU_VERIFY(request->bmRequestType == 0xA2); // in,class,EP
+    TU_VERIFY(request->wLength == 1u);
+    usbtmc_get_clear_status_rsp_t clearStatusRsp = {0};
+    tmcStatusCode = USBTMC_STATUS_FAILED;
+    usbd_edpt_xfer(rhport, 0u, (void*)&tmcStatusCode,sizeof(tmcStatusCode));
+    return true;
+  }
+
+  case USBTMC_bREQUEST_INITIATE_ABORT_BULK_IN:
+  {
+    usbtmc_initiate_abort_rsp_t rsp = {0};
+    uart_tx_str_sync("init abort bulk in\r\n");
+    TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
+    TU_VERIFY(request->wLength == sizeof(tmcStatusCode));
+    TU_VERIFY(request->wIndex == usbtmc_state.ep_int_in);
+    // wValue is the requested bTag to abort
+    usbtmc_state.transfer_size_remaining = 0;
+    usbtmc_state.state = STATE_ABORTING_BULK_IN;
+    TU_VERIFY(usbtmcd_app_initiate_clear(rhport, &tmcStatusCode));
+    TU_VERIFY(tud_control_xfer(rhport, request, (void*)&tmcStatusCode,sizeof(tmcStatusCode)));
+    return true;
+  }
 
   case USBTMC_bREQUEST_INITIATE_CLEAR:
     {
+      uart_tx_str_sync("init clear\r\n");
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
       TU_VERIFY(request->wLength == sizeof(tmcStatusCode));
       // After receiving an INITIATE_CLEAR request, the device must Halt the Bulk-OUT endpoint, queue the
       // control endpoint response shown in Table 31, and clear all input buffers and output buffers.
       usbd_edpt_stall(rhport, usbtmc_state.ep_bulk_out);
+      usbtmc_state.transfer_size_remaining = 0;
+      usbtmc_state.state = STATE_CLEARING;
       TU_VERIFY(usbtmcd_app_initiate_clear(rhport, &tmcStatusCode));
       TU_VERIFY(tud_control_xfer(rhport, request, (void*)&tmcStatusCode,sizeof(tmcStatusCode)));
       return true;
@@ -450,17 +586,31 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
 
   case USBTMC_bREQUEST_CHECK_CLEAR_STATUS:
     {
-      usbtmc_get_clear_status_rsp_t clearStatusRsp = {0};
+      uart_tx_str_sync("check clear\r\n");
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
+      usbtmc_get_clear_status_rsp_t clearStatusRsp = {0};
       TU_VERIFY(request->wLength == sizeof(clearStatusRsp));
-      TU_VERIFY(usbtmcd_app_get_clear_status(rhport, &clearStatusRsp));
 
+      if(usbd_edpt_busy(rhport, usbtmc_state.ep_bulk_in))
+      {
+        // Stuff stuck in TX buffer?
+        clearStatusRsp.bmClear.BulkInFifoBytes = 1;
+        clearStatusRsp.USBTMC_status = USBTMC_STATUS_PENDING;
+      }
+      else
+      {
+        // Let app check if it's clear
+        TU_VERIFY(usbtmcd_app_get_clear_status(rhport, &clearStatusRsp));
+      }
+      if(clearStatusRsp.USBTMC_status == USBTMC_STATUS_SUCCESS)
+        usbtmc_state.state = STATE_IDLE;
       TU_VERIFY(tud_control_xfer(rhport, request, (void*)&clearStatusRsp,sizeof(clearStatusRsp)));
       return true;
     }
 
   case USBTMC_bREQUEST_GET_CAPABILITIES:
     {
+      uart_tx_str_sync("get capabilities\r\n");
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
       TU_VERIFY(request->wLength == sizeof(usbtmcd_app_capabilities));
       TU_VERIFY(tud_control_xfer(rhport, request, (void*)&usbtmcd_app_capabilities, sizeof(usbtmcd_app_capabilities)));
@@ -470,6 +620,7 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
 
   case USBTMC_bREQUEST_INDICATOR_PULSE: // Optional
     {
+      uart_tx_str_sync("indicate\r\n");
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
       TU_VERIFY(request->wLength == sizeof(tmcStatusCode));
       TU_VERIFY(usbtmcd_app_capabilities.bmIntfcCapabilities.supportsIndicatorPulse);
@@ -482,6 +633,7 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
     // USB488 required requests
   case USBTMC488_bREQUEST_READ_STATUS_BYTE:
     {
+      uart_tx_str_sync("read stb\r\n");
       usbtmc_read_stb_rsp_488_t rsp;
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
       TU_VERIFY(request->wLength == sizeof(rsp)); // in,class,interface
@@ -520,6 +672,7 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
   case USBTMC488_bREQUEST_GO_TO_LOCAL:
   case USBTMC488_bREQUEST_LOCAL_LOCKOUT:
     {
+      uart_tx_str_sync("Unsupported REN/GTL/LLO\r\n");
       TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
       TU_VERIFY(false);
       return false;
@@ -527,6 +680,7 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
 #endif
 
   default:
+    uart_tx_str_sync("Default CTRL handler\r\n");
     TU_VERIFY(false);
     return false;
   }