diff --git a/examples/device/usbtmc/src/main.c b/examples/device/usbtmc/src/main.c
index 8bc2a8398..1fce48f45 100644
--- a/examples/device/usbtmc/src/main.c
+++ b/examples/device/usbtmc/src/main.c
@@ -29,7 +29,7 @@
 
 #include "bsp/board.h"
 #include "tusb.h"
-
+#include "usbtmc_app.h"
 //--------------------------------------------------------------------+
 // MACRO CONSTANT TYPEDEF PROTYPES
 //--------------------------------------------------------------------+
@@ -60,6 +60,7 @@ int main(void)
   {
     tud_task(); // tinyusb device task
     led_blinking_task();
+    usbtmc_app_task_iter();
   }
 
   return 0;
diff --git a/examples/device/usbtmc/src/usb_descriptors.c b/examples/device/usbtmc/src/usb_descriptors.c
index 296636359..9567bcab5 100644
--- a/examples/device/usbtmc/src/usb_descriptors.c
+++ b/examples/device/usbtmc/src/usb_descriptors.c
@@ -110,10 +110,10 @@ uint8_t const * tud_hid_descriptor_report_cb(void)
      USBTMC_BULK_DESCRIPTORS(/* OUT = */0x03, /* IN = */ 0x83)
 
 #if defined(CFG_TUD_USBTMC_ENABLE_INT_EP)
-
+// Interrupt endpoint should be 2 bytes on a FS USB link
 #  define USBTMC_DESC(_itfnum) \
      USBTMC_DESC_MAIN(_itfnum, /* _epCount = */ 3), \
-     USBTMC_INT_DESCRIPTOR(/* INT ep # */ 0x84, /* epMaxSize = */ 64, /* bInterval = */16u )
+     USBTMC_INT_DESCRIPTOR(/* INT ep # */ 0x84, /* epMaxSize = */ 2, /* bInterval = */16u )
 #  define USBTMC_DESC_LEN (USBTMC_IF_DESCRIPTOR_LEN + USBTMC_BULK_DESCRIPTORS_LEN + USBTMC_INT_DESCRIPTOR_LEN)
 
 #else
@@ -248,7 +248,7 @@ uint16_t const* tud_descriptor_string_cb(uint8_t index)
   }
 
   // first byte is length (including header), second byte is string type
-  _desc_str[0] = (TUSB_DESC_STRING << 8 ) | (2*chr_count + 2);
+  _desc_str[0] = (((uint16_t)TUSB_DESC_STRING) << 8 ) | (2u*chr_count + 2u);
 
   return _desc_str;
 }
diff --git a/examples/device/usbtmc/src/usbtmc_app.c b/examples/device/usbtmc/src/usbtmc_app.c
index 6b72bb360..af97939b9 100644
--- a/examples/device/usbtmc/src/usbtmc_app.c
+++ b/examples/device/usbtmc/src/usbtmc_app.c
@@ -25,6 +25,7 @@
 
 #include <strings.h>
 #include "class/usbtmc/usbtmc_device.h"
+#include "bsp/board.h"
 #include "main.h"
 
 #if (USBTMC_CFG_ENABLE_488)
@@ -65,9 +66,21 @@ usbtmcd_app_capabilities  =
 };
 
 static const char idn[] = "TinyUSB,ModelNumber,SerialNumber,FirmwareVer\n";
-static uint8_t status;
-static bool queryReceived = false;
+static volatile uint8_t status;
 
+// 0=not query, 1=queried, 2=delay,set(MAV), 3=delay 4=ready?
+// (to simulate delay)
+static volatile uint16_t queryState = 0;
+static volatile uint32_t queryDelayStart;
+static volatile uint32_t bulkInStarted;
+
+static usbtmc_msg_dev_dep_msg_in_header_t rspMsg = {
+    .bmTransferAttributes =
+    {
+      .EOM = 1,
+      .UsingTermChar = 0
+    }
+};
 
 bool usbtmcd_app_msgBulkOut_start(uint8_t rhport, usbtmc_msg_request_dev_dep_out const * msgHeader)
 {
@@ -86,7 +99,7 @@ bool usbtmcd_app_msg_data(uint8_t rhport, void *data, size_t len, bool transfer_
   (void)rhport;
   (void)transfer_complete;
   if(transfer_complete && (len >=4) && !strncasecmp("*idn?",data,4)) {
-    queryReceived = true;
+    queryState = 1;
   }
   return true;
 }
@@ -98,47 +111,73 @@ bool usbtmcd_app_msgBulkIn_complete(uint8_t rhport)
 }
 
 static uint8_t noQueryMsg[] = "ERR: No query\n";
+
 bool usbtmcd_app_msgBulkIn_request(uint8_t rhport, usbtmc_msg_request_dev_dep_in const * request)
 {
-  usbtmc_msg_dev_dep_msg_in_header_t hdr = {
-      .header =
-      {
-          .MsgID = request->header.MsgID,
-          .bTag = request->header.bTag,
-          .bTagInverse = request->header.bTagInverse
-      },
-      .TransferSize = sizeof(idn)-1,
-      .bmTransferAttributes =
-      {
-        .EOM = 1,
-        .UsingTermChar = 0
-      }
-  };
-  if(queryReceived)
+  rspMsg.header.MsgID = request->header.MsgID,
+  rspMsg.header.bTag = request->header.bTag,
+  rspMsg.header.bTagInverse = request->header.bTagInverse;
+  if(queryState != 0)
   {
-    usbtmcd_transmit_dev_msg_data(rhport, &hdr, idn);
+    TU_ASSERT(bulkInStarted == 0);
+    bulkInStarted = 1;
   }
   else
   {
-    hdr.TransferSize = sizeof(noQueryMsg)-1;
-    usbtmcd_transmit_dev_msg_data(rhport, &hdr, noQueryMsg);
+    rspMsg.TransferSize = sizeof(noQueryMsg)-1;
+    usbtmcd_transmit_dev_msg_data(rhport, &rspMsg, noQueryMsg);
   }
-  queryReceived = false;
+  // Always return true indicating not to stall the EP.
   return true;
 }
 
+void usbtmc_app_task_iter(void) {
+  uint8_t const rhport = 0;
+
+  switch(queryState) {
+  case 1:
+    queryDelayStart = board_millis();
+    queryState = 2;
+    break;
+  case 2:
+    if( (board_millis() - queryDelayStart) > 1000u) {
+      queryDelayStart = board_millis();
+      queryState=3;
+      status |= 0x10u; // MAV
+    }
+    break;
+  case 3:
+    if( (board_millis() - queryDelayStart) > 1000u) {
+      queryState = 4;
+    }
+    break;
+  case 4: // time to transmit;
+    if(bulkInStarted) {
+      queryState = 0;
+      bulkInStarted = 0;
+      rspMsg.TransferSize = sizeof(idn)-1;
+      usbtmcd_transmit_dev_msg_data(rhport, &rspMsg, idn);
+      status &= ~(0x10u); // MAV
+    }
+    break;
+  }
+}
+
 // Return status byte, but put the transfer result status code in the rspResult argument.
-uint8_t usbtmcd_app_get_stb(uint8_t rhport, uint8_t *rspResult)
+uint8_t usbtmcd_app_get_stb(uint8_t rhport, uint8_t *tmcResult)
 {
   (void)rhport;
-  *rspResult = USBTMC_STATUS_SUCCESS;
+  *tmcResult = USBTMC_STATUS_SUCCESS;
   // Increment status so that we see different results on each read...
-  status++;
 
   return status;
 }
 
-bool usbtmcd_app_indicator_pluse(uint8_t rhport, tusb_control_request_t const * msg)
+bool usbtmcd_app_indicator_pluse(uint8_t rhport, tusb_control_request_t const * msg, uint8_t *tmcResult)
 {
+  (void)rhport;
+  (void)msg;
   led_indicator_pulse();
+  *tmcResult = USBTMC_STATUS_SUCCESS;
+  return true;
 }
diff --git a/examples/device/usbtmc/src/usbtmc_app.h b/examples/device/usbtmc/src/usbtmc_app.h
new file mode 100644
index 000000000..4de30c2ba
--- /dev/null
+++ b/examples/device/usbtmc/src/usbtmc_app.h
@@ -0,0 +1,7 @@
+
+#ifndef USBTMC_APP_H
+#define USBTMC_APP_H
+
+void usbtmc_app_task_iter(void);
+
+#endif
diff --git a/src/class/usbtmc/usbtmc_device.c b/src/class/usbtmc/usbtmc_device.c
index 7bc768a58..db0c95a32 100644
--- a/src/class/usbtmc/usbtmc_device.c
+++ b/src/class/usbtmc/usbtmc_device.c
@@ -379,9 +379,11 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
 #if (USBTMC_CFG_ENABLE_488)
   ushort bTag;
 #endif
-  // We only handle class requests.
+  // We only handle class requests, IN direction.
   if(request->bmRequestType_bit.type != TUSB_REQ_TYPE_CLASS)
+  {
     return false;
+  }
 
   switch(request->bRequest)
   {
@@ -390,27 +392,38 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
   case USBTMC_bREQUEST_CHECK_ABORT_BULK_OUT_STATUS:
   case USBTMC_bREQUEST_INITIATE_ABORT_BULK_IN:
   case USBTMC_bREQUEST_CHECK_ABORT_BULK_IN_STATUS:
+    TU_VERIFY(request->bmRequestType == 0xA2); // in,class,EP
+    TU_VERIFY(false);
+    break;
+
   case USBTMC_bREQUEST_INITIATE_CLEAR:
   case USBTMC_bREQUEST_CHECK_CLEAR_STATUS:
+    TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
     TU_VERIFY(false);
     break;
 
   case USBTMC_bREQUEST_GET_CAPABILITIES:
-    TU_VERIFY(request->bmRequestType == 0xA1);
+    TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
     TU_VERIFY(request->wValue == 0x0000);
     TU_VERIFY(request->wIndex == usbtmc_state.itf_id);
     TU_VERIFY(request->wLength == sizeof(usbtmcd_app_capabilities));
     TU_VERIFY(tud_control_xfer(rhport, request, (void*)&usbtmcd_app_capabilities, sizeof(usbtmcd_app_capabilities)));
     return true;
   // USBTMC Optional Requests
+
   case USBTMC_bREQUEST_INDICATOR_PULSE: // Optional
+    TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
     TU_VERIFY(usbtmcd_app_capabilities.bmIntfcCapabilities.supportsIndicatorPulse);
-    TU_VERIFY(usbtmcd_app_indicator_pluse(rhport, request));
+    uint8_t tmcResult;
+    TU_VERIFY(usbtmcd_app_indicator_pluse(rhport, request, &tmcResult));
+    TU_VERIFY(tud_control_xfer(rhport, request, (void*)&tmcResult, sizeof(tmcResult)));
+
     return true;
 
 #if (USBTMC_CFG_ENABLE_488)
     // USB488 required requests
   case USBTMC488_bREQUEST_READ_STATUS_BYTE:
+    TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
 
     bTag = request->wValue & 0x7F;
     TU_VERIFY(request->bmRequestType == 0xA1);
@@ -444,6 +457,7 @@ bool usbtmcd_control_request(uint8_t rhport, tusb_control_request_t const * requ
   case USBTMC488_bREQUEST_REN_CONTROL:
   case USBTMC488_bREQUEST_GO_TO_LOCAL:
   case USBTMC488_bREQUEST_LOCAL_LOCKOUT:
+    TU_VERIFY(request->bmRequestType == 0xA1); // in,class,interface
     TU_VERIFY(false);
     return false;
 #endif
diff --git a/src/class/usbtmc/usbtmc_device.h b/src/class/usbtmc/usbtmc_device.h
index 09cda7c67..84640b136 100644
--- a/src/class/usbtmc/usbtmc_device.h
+++ b/src/class/usbtmc/usbtmc_device.h
@@ -64,10 +64,11 @@ bool usbtmcd_app_msgBulkIn_request(uint8_t rhport, usbtmc_msg_request_dev_dep_in
 
 bool usbtmcd_app_msgBulkIn_complete(uint8_t rhport);
 
-TU_ATTR_WEAK bool usbtmcd_app_indicator_pluse(uint8_t rhport, tusb_control_request_t const * msg);
+// Indicator pulse should be 0.5 to 1.0 seconds long
+TU_ATTR_WEAK bool usbtmcd_app_indicator_pluse(uint8_t rhport, tusb_control_request_t const * msg, uint8_t *tmcResult);
 
 #if (USBTMC_CFG_ENABLE_488)
-uint8_t usbtmcd_app_get_stb(uint8_t rhport, uint8_t *rspResult);
+uint8_t usbtmcd_app_get_stb(uint8_t rhport, uint8_t *tmcResult);
 TU_ATTR_WEAK bool usbtmcd_app_msg_trigger(uint8_t rhport, usbtmc_msg_generic_t* msg);
 //TU_ATTR_WEAK bool usbtmcd_app_go_to_local(uint8_t rhport);
 #endif